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FINAL REPORT

English River Watershed Plan

Kalona, Iowa

53:084 Project Design and Management The University of Iowa

Prepared for: Professor Larry W eber , The University of Iowa - I I H R

Professor Jacob Odgaard, The University of Iowa - I I H R

Prepared by A nvil Engineer ing Submitted: May 9, 2011

University of Iowa Civil Engineering Dept. 4105 Seamans Center Iowa City, IA 52242 (860) 287-2840 [email protected]

1

May 3, 2011 Professor Larry Weber University of Iowa IIHR Hydroscience and Engineering 107C Stanley Hydraulics Lab Iowa City, IA 52242 RE: Kalona, Iowa, English River Watershed Plan Dear Professor Weber, As per your request attached are four (4) copies of the final report for the Kalona, Iowa, English River Watershed project. The final report includes an executive summary, statement of design objectives, three completed design tasks, and associated technical details. Anvil Engineering has enjoyed working with you and the city of Kalona developing designs for the future of the English River Watershed. Sincerely, Jonathan Durst Project Manager Enclosures

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Final Report Kalona, Iowa, English River Watershed Plan

Anvil Engineering Page | 1

Executive Summary

Anvil Engineering is a small engineering firm based out of Iowa City, Iowa. The firm was

contracted to complete three preliminary design tasks for Kalona, Iowa. The design tasks;

characterizing the English River Watershed, developing preliminary designs for upgrades to

plain maps, were

expeditiously completed by experience in water resource

management and water quality protection.

Each design task is discussed sequentially in further detail within the report. The task to

characterize the watershed and analyze the FEMA flood maps (Task 1 and 3, respectively) did

not require preliminary designs. These two tasks were instead oriented to provide the City of

Kalona with a basic set of technical data for the use on future projects and as a general reference

for any interested parties. A sample of the provided information is as follows: the projected

100-year flow rate in the English River is roughly 225,000 gallons per second with a water level

of 657 feet above mean sea level (Task 1, Section 1.2) and 401 parcels amounting to $46.9

million in property value are entirely within the 100-year flood plain according to new FEMA

flood map (Task 3, Section 3.0).

Task 2, upgrades to the western creek drainage, did require the development of multiple

alternative designs. Two preliminary designs were considered for the creek; bank stabilization in

order to convey higher flows and minimize bank erosion, and bank stabilization in conjunction

with a detention pond north of Kalona to moderate peak flows. The former alternative, utilizing

bank stabilization, was chosen as the preferred alternative. This decision was made by the use of

selection criteria and is discussed further in sections 2.3 and 2.4 of the report.

The cost of these improvements to the west creek was estimated at $6 million. The construction

timeline of the bank stabilizing improvements is subject to the unknown variables of necessary

design improvements to the four bridge/culvert structures and stormwater outfalls along the

length of the creek. Additionally, Anvil recommends the use of simple rain and stream gages

within the creek watershed and channel in order to provide the contracted design firm with

specific data for the west creek.

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The main challenge Anvil Engineering overcame during this preliminary design project was to

obtain an appropriately detailed set of data in order to generate basic hydraulic models of the

west creek drainage and English River watershed. Resourcefulness on the part of Anvil

personnel and generous help from Kalona

were crucial to the success of this project.

The total cost of the English River Watershed Plan is $42,500. This amount was derived by

computing Anvil Engineering hourly rates for hours logged during the course of the 13-week

project with the addition of extraneous costs. Please refer to Appendix C for additional

budgetary information.

Anvil Engineering is proud to have provided Kalona with a detailed preliminary technical and

design report, and looks forward to continuing to serve the city with our experience in water

resource management, enthusiastic dedication to high quality results, and client satisfaction.

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Table of Contents 0.0: Project Background Information ..........................................................................................5

1.0: TASK 1 Characterization of the English River Watershed ................................................9

1.1: Land Use ....................................................................................................................... 10

1.2: USGS Gage Analysis .................................................................................................... 13

1.3: Watershed Improvements .............................................................................................. 16

1.3.1 Reservoir Systems: ................................................................................................... 16

1.3.2 Environmental Rehabilitation: .................................................................................. 20

2.0: TASK 2 Preliminary Design Alternatives for Creek Improvements ................................ 23

2.1: Design Objectives.......................................................................................................... 27

2.2: Alternative Solutions ..................................................................................................... 29

2.2.1: Alternative 1 Bank Stabilization........................................................................... 33

2.2.2: Alternative 2 Bank Stabilization with Detention Pond .......................................... 36

2.3: Selection Criteria and Weighting Factors ....................................................................... 38

2.4: Selection Matrix ............................................................................................................ 39

2.5: Summary of Task 2 Design............................................................................................ 40

3.0: TASK 3 FEMA Map Analysis ........................................................................................ 41

4.0: About Anvil Engineering................................................................................................... 44

5.0: Project Summary ............................................................................................................... 45

6.0 References ........................................................................................................................... 46

Appendix A: Task 1 Supplemental Information ........................................................................ 48

A.1: Description of land use categories ................................................................................. 48

A.2: Hypothetical Reservoir System Design & Cost ............................................................. 50

A.3: Hypothetical Riparian Rehabilitation Design & Cost .................................................... 53

Appendix B: Task 2 Supplemental Information ........................................................................ 56

B.1: Data Sets and Models.................................................................................................... 56

B.1.1: WinTR-55 West Creek Flows ................................................................................ 56

B.1.2: HEC-RAS West Creek Hydrologic Model.............................................................. 68

B.2: Alternative 1 Design and Cost Calculations .................................................................. 71

B.2.1: Channel Side Slope and Coverage Area ................................................................. 71

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B.2.2: Sample Calculation Station 15234.77 .................................................................. 73

B.2.3: Costs ...................................................................................................................... 77

B.2.4: Summary Table ...................................................................................................... 78

B.3: Alternative 2 Design and Cost Calculations .................................................................. 79

B.3.1: Detention Pond Sizing ............................................................................................ 79

B.3.2: Costs ...................................................................................................................... 80

B.3.3: Summary Table ...................................................................................................... 81

B.4: Recommended Design Alternative Construction Information ........................................ 82

B.4.1 Permitting: ............................................................................................................... 82

Appendix C: Anvil Engineering Project Costs .......................................................................... 83

C.1: Anvil Engineering Annual Operating Expenses Summary ............................................. 83

C.2: Direct and Indirect Cost Breakdown ............................................................................. 84

C.3: Annual Operating Expenses Calculations ...................................................................... 85

Appendix D: Additional figure information .............................................................................. 87

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0.0: Project Background Information

Kalona, Iowa is a small city located in the southeast quadrant of Iowa along the English River

(Figure 1). The population of Kalona, Iowa according to the 2000 census was 2,293 persons

with a 2010 population growth for Washington County of roughly 5 to 15% (U.S. Census

Bureau, 2011). Kalona has experienced numerous flooding events within the last decade due to

a number of factors. These factors include: unfavorable weather patterns; the

the relatively flat, traditional English River flood plain; and three creek drainages prone to flash

flooding within the city limits. A brief assessment of the United States Geological Survey

(USGS) stream gage located south of Kalona by the Highway 1 bridge places English River peak

annual flows from 2008, 2009, and 2010 all within the top 20 highest river flows on record

(USGS, 2010). With the frequency of flooding disasters in the county, the Federal Emergency

Management Agency (FEMA) has accordingly produced new flood maps for the region (FEMA,

2011). The newly mapped flood plain delineations place approximately 75% of Kalona within

the 100-year high risk flood zone (Figure 2).

Figure 1: Map of Iowa showing the location of Kalona, Iowa and proximity of the city to the English River (Geology.com, 2011).

K alona, Iowa

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Figure 2: Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM). Areas of Kalona, Iowa highlighted with blue are considered to be within the 100-year flood plain (Zone A).

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Understandably citizens of Kalona are very concerned about the implications of the new flood

plain maps; specifically how to translate the maps into the implied risk and the financial burdens

of the National Flood Insurance Program (NFIP). Anvil Engineering was therefore given three

tasks to help city officials address a portion of these concerns.

The first task was to characterize the English River Watershed and perform a standard analysis

of the English River USGS gage (Figure 3). From the analysis it was determined that the

majority (87.9%) of the watershed is used as crop land, pasture, or grassland; and the 100-year

flood flows are approximately 30,000 cubic feet per second (cfs) with a water elevation of 657

feet above mean sea level at the gage site (USGS, 2010). Accompanying this analysis is the

discussion of two potential watershed improvements to reduce peak flows.

Figure 3: Map depicting the English River Watershed upstream of the USGS stream gage (blue dot) located near Kalona, Iowa (red dot) (Iowa Flood Center, 2011)

The second and third tasks were assigned by Kalona City Administrator, Ryan Schlabaugh. Due

to the frequency of flash flooding of the intra-city creek drainages and the issuance of new flood

plain mapping by FEMA, Mr. Schlabaugh expressed interest in potential improvements to the

creek systems in Kalona; specifically the west creek, the largest of the three creek drainages, and

an analysis of the flood maps. Anvil Engineering therefore made interests our

second and third tasks, respectively. The analysis of the FEMA maps (Task 3) culminated in the

K alona, Iowa English River Watershed

USGS Gage

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creation of a color coded parcel map to help homeowners visualize the impact of the flood plain

on their property. Task 2, the preliminary design of two creek upgrade alternatives yielded a

recommended design; the use of bank stabilization techniques (riprap and gabion baskets) to

increase the conveyance and minimize erosion of the west creek.

The report is broken up by task. Task 1 and 3 are relatively shorter than Task 2, due to these

tasks requiring only the discussion of factual information to be used by Kalona as a resource.

Task 2 required the preliminary design of two alternatives; therefore, it contains a larger number

of sections relative to Task 1 and 3. Task 1, the characterization of the English River watershed,

is first to be discussed and appropriately so, due to the information gained from the analysis of

the English River being carried forward to the remaining tasks.

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1.0: T ASK 1 Character ization of the E nglish River Watershed

Historically the holistic approach of improving an entire watershed has not been widely

practiced. This is due to a variety of reasons; for example, the complication of coordinating the

needs and wants of numerous private and public entities, the relatively large sums of money

needed for construction, and the lack of general hydrologic understanding. In an effort to

provide the City of Kalona with a basic set of factual information, Anvil Engineering has

analyzed the land use in the English River Watershed and the USGS river gage located south of

Kalona with a discussion of the results (Sections 1.1 and 1.2, respectively). Two alternative

options for watershed improvement are also discussed in the final section of Task 1 (Section

1.3). Accompanying the discussions of alternatives are hypothetical calculations for the design

and costs of each alternative. Since these designs are simply hypothetical and not specific to any

area in the English River Watershed, it should be understood that the costs associated with the

designs are only the rough approximation of material costs. The following section will begin

with a discussion of land use within the English River Watershed.

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1.1: Land Use

The purpose for exploring the land use in the watershed is to help characterize the sources or

potential causes of large amounts of runoff contributing to flood events. The statistical

breakdown in Table 1 shows that the majority of land (87.9%) in the English River Watershed is

used as row crop, pasture, or grassland, all of which are not ideal for the infiltration of rainwater.

By not infiltrating rainwater, these land areas will tend to convey more rainwater as runoff

(Mays, 2005). This runoff then translates to higher stream and subsequently river flows with the

potential to cause flooding. The land use for the watershed is graphically presented in Figure 4

with the use of a U.S. Department of Agriculture (USDA) map.

Table 1: Statistical breakdown of land use in the English River Watershed.

(Definitions of land use categories can be found in Appendix A.1)

To exemplify the importance of land use we will consider two types of land use in the context of

the USDA Natural Resources Conservation Service (NRCS) curve number (CN) method. The

two land use practices to be compared will be: Case 1 straight row crops with soil in good

hydrologic condition (~58% of the English River Watershed), and Case 2 deciduous forest land

in good hydrologic condition (~4% of the watershed). Assuming a class B soil (shallow loess,

sandy loam soils), the potential maximum retention of water by land in Case 1 is 2.82 inches, and

Percentage of Watershed

Type of Landuse

0.15% Open Water4.57% Developed, Open Space1.59% Developed, Low Intensity0.14% Developed, Medium Intensity0.03% Developed, High Intensity0.02% Barren Land3.92% Deciduous Forest0.01% Evergreen Forest12.60% Grassland16.97% Pasture/Hay58.33% Cultivated Cropland1.40% Woody Wetlands0.28% Emergent Wetlands

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for Case 2, 7.24 inches (Mays, 2005). Therefore a forested area can infiltrated nearly three times

the amount of rainwater infiltrated in an area used for row crops, or three times less water

becomes runoff into streams thereby potentially mitigating a flood event. Again these numbers

are only meant to show the importance of land use when discussing causes of peak flow events

in streams and rivers.

From the statistics in Table 1 it can be surmised that any sufficiently large storm (i.e. greater than

6 inches over a short duration) within the basin will cause a good amount of runoff and have the

potential to cause the English River to reach a flood stage. The next section discusses the

statistical analysis of the USGS stream gage situated in the English River and how these data are

translated into expected flows and levels for flood events with various return periods (i.e. the

100-year flood).

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(Source: National Land Cover Data Set (NLCD), by Multi-Resolution Land Characteristics (MRLC) Consortium - USGS, EPA, NOAA, SFS, BLM, NASA, NPS, NRCS, USFWS, OSM.)

Figure 4: Graphical depiction of the English River Watershed and associated land use. A statistical breakdown of land use is available in Table 1.

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1.2: USGS Gage A nalysis

Kalona, Iowa is situated directly north of the English River. The nearest USGS river gage is to

the east of the highway 1 bridge on the south bank of the English River (Figure 5). The function

of a USGS river gage is to record river flows and associated water levels over time. This then

allows professionals to perform statistical analyses on the river data which culminate in values

for flood flows and levels. Therefore the gage south of Kalona, with records dating as far back

as 1930, is in an ideal location for this project.

The current, preferred technique for analysis is the Log-Pearson method; a statistical analysis of

the annual peak flow data with the use of a skew factor. The results from the Log-Pearson

method are presented in Table 2. The correlation of flows to gage levels was accomplished by

fitting an exponential trend line to a graph of peak flows and gage height (Figure 6).

Figure 5: USGS English River Gage location in relation to Kalona, IA.

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Table 2: Results of Log-Pearson Analysis of USGS peak annual flow gage data. Gage height was calculated using the exponential trend line in Figure 2. Mean sea level is the addition of the gage height to the gage datum of 633.45

Figure 6: Plotted peak annual flow data for the USGS gage located on the English River south of Kalona, IA. A best fit exponential line was applied to the data to correlate flows to gage heights in Table 1.

The reason for the flood range in Table 2 is due to the skew factors used in the Log-Pearson

analysis. As a statistical analysis the Log-Pearson method makes use of factors such as the

mean, standard deviation, and root mean square of the data. From these terms a skew factor is

Return Period

Gage Height

Mean Sea Level

(ft)2 6100 6173 15.3 648.75 11065 11096 18.4 651.810 15104 14977 20.0 653.525 21046 20532 21.7 655.250 26077 25099 22.9 656.3100 31608 29997 23.9 657.3200 37722 35296 24.8 658.2

Flow Range (cfs)

y = 1376.5x -‐ 13246R² = 0.6836

y = 327.46e0.1915xR² = 0.9503

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5 10 15 20 25

River F

low (cfs)

Gage Height (ft)

Peak Flow & Height 1930 -‐ 2009

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generated with the correlation to tabulated data. The skew factor for the English River was in

between to two numbers and therefore both numbers were computed to yield the flow range

reported in Table 2.

The most prevalent numbers within the table are for the 100-year flood. To begin the name 100-

year flood refers to the flood with a 100-year return period. Return period is a statistical term

that is better interpreted not as the flood that occurs once every 100 years, but rather as the flood

that has a 1% chance of occurrence every year. The analysis gives the flow and gage level with a

1% yearly risk as roughly 30,000 cubic feet per second (~225,000 gallons per second) at 657 feet

above mean sea level. This flow is sufficient to fill one Olympic-sized swimming pool every

three seconds.

These flows are considerable and floods, as most resident of the Midwest know, are devastating

natural disasters. There are solutions available to communities living within flood plains to help

reduce the risk of flooding. Many solutions utilized are local in nature (i.e. levees, flood walls,

etc ), but there is a growing focus on solutions that are regional; encompassing the entire

watershed. The next section briefly describes two such solutions. Realistically some

combination of solutions is typically best suited for each case.

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1.3: Watershed Improvements

1.3.1 Reservoi r Systems:

Detention and retention basins are structures frequently used in flood control projects. Both

types of basins have the same purpose, to slow the flow of water while on its path to connecting

tributaries, but differ in how they function. As stated in Water-Resources Engineering by David

A. Chin, detention basins are water-storage areas where the stored water is released gradually

through an uncontrolled outlet, and retention basins are water storage areas where there is either

no outlet or the impounded water is stored for a prolonged period, effectively creating a pond or

reservoir. Therefore a retention basin increases the amount of water runoff that permeates into

the ground by ponding. Retention basin may also have an emergency spill way or outlet

structure to release water if the level in the pond or reservoir exceeds a given height. An image

of a typical retention basin is shown below as Figure 8.

Like retentions basins, detention basins can also pool water. For example, the reservoir behind

the Hoover Dam is considered a detention basin because the water is detained and exits through a

controlled, continuous flow outlet. Detention basins where the basin constantly contains water

are known to as wet-detention basins or detention ponds. A schematic of a detention basin is

displayed in Figure 9. When a detention basin is designed to only fill with water at certain times

but remain empty otherwise it is called a dry-detention basin (Figure 7) (Chin, 2006). Detention

basins may also have ancillary functions. For instance basins can be designed to provide greater

storm water quality by allowing sediment to settle out of the accumulated runoff or function as a

habitat preserve. In general retention and detention basins may be thought of as designated

floodable areas, thereby reducing the amount of water downstream. For example, the particular

basin shown in Figure 7 is filled with water when its downstream drainage is backed up. By

designing this area to contain the backed up water the housing nearby is then better protected

from flooding due to heavy river or stream flows.

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Figure 9: Schematic of a Detention Basin, (Iowa Stormwater Management, 2009)

Another good way to visualize the utility of detention basins is to think of a side-by-side kitchen

sink. Image if the water slowly flowing out of the faucet is a river and the sink drain is partially

plugged simulating a dam. This scenario would represent a wet-detention pond if the water

builds up in the sink but eventually the flow out of the faucet and flow out the drain become

equal. Detention basins also often have emergency overflow sections which are represented in

this example by the sink partition. If water level in the primary sink exceeds this partition it will

overflow the partition into the adjacent sink and flow out the secondary sink drain. A dry-

Figure 8: Typical Retention Basin Figure 7: Urban Detention (Dry) Basin

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detention basin is very similar with only minor differences. Instead of immediately ponding the

water, any nominal flow into the sink may escape unimpeded through the drain. Only when high

flow events from a large storm or excessive snow melt will the basin or sink begin to pond the

water. In the sink example this could be simulated by dumping a bucket of water into the sink.

The flow from the bucket would greatly exceed the ability of the sink drain and thus, water

would pond. Eventually the water in the basin will drain, but downstream areas will be protected

from the spurious high flow events and therefore be less apt to flood.

To appropriately apply a detention basin plan to the English River Watershed we must first gain

a better understanding of the watershed itself. Using geographic information sources (USDA),

the English River is roughly 85 miles in length and is fed by three other rivers; the Deep, Middle

English, and South English Rivers are all tributaries of the English River. The English River

Watershed drains roughly 640 square miles (Iowa DNR, 2009) and, as listed in Table 2, the 100

year flow for the English River at Kalona, Iowa is approximately 30,000 cubic feet per second

(cfs) which correlates to a water surface level of 657 feet above sea level. These water levels

and flows are significant and have the potential to cause great damage to the City of Kalona.

(FEMA, 2011)

watershed or tributaries would provide a method of controlling runoff flows to the English River

and therefore reduce the risk of flooding for Kalona and other communities within the English

River flood plain. For example, due to the installation of the Coralville Dam and Reservoir in

Coralville, Iowa, an estimated $66.5 million in damages were prevented during the 2008 flood

(Coralville Lake Fact Sheet, 2010). Although these two situations may seem quite different, the

message is clear, detention basins have the potential to significantly reduce the amount of

damage caused by flooding.

The largest obstacle preventing a watershed based strategy to reduce the risk of flooding in the

English River is the fact that the English River Watershed spans across the jurisdiction of many

individual property owners and governmental entities. In order to develop and implement an

effective plan for the installation of flood prevention structures the coordination and interests of

each affected party would have to be understood and a compromise reached. The difficulty

being that some parties may have to make the sacrifices of land or money in order to help

everyone else. Additionally, the funding for an English River flood prevention project would

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also become a limit. Though currently, due to recent flooding in the state of Iowa, flood

prevention and mitigation projects are receiving increased attention by communities as well as

funding programs. Two programs involved in funding flood prevention and water quality

projects in the state of Iowa include the Watershed Protection Fund (WSPF) and the Watershed

Improvement Review Board (WIRB).

The WIRB is a 15-member board consisting of various environmental specialists and state

representatives. (Iowa Department of Agriculture and Land Stewardship: FAQ, 2011) It was

founded in 2005 to award grants to applicants to improve water quality and flood prevention.

The funds administered by the WIRB are appropriations made by the Iowa Legislature. In order

to obtain funds a community must complete an application prior to an announced Request for

Application deadline. In the years of 2009 and 2010 there were five separate application

deadlines with a total of 66 applicants. Of the 66 applicants, 38 of them were awarded funds.

The funds awarded for the years of 2009 and 2010 together totaled $11.1 million and ranged

from $500,000 to $33,000 for each applicant (2009 Annual Report, 2010) (2010 Annual Report,

2011). It should be noted that matching funds are not required for applicants; however,

leveraging of funds and local commitment are two criteria the Board uses to evaluate

applications (Iowa Department of Agriculture and Land Stewardship: FAQ, 2011). Greater

details are provided in the WIRB program section on the Iowa Department of Agriculture and

Land Stewardship website.

The information provided is intended to provide the reader with an overview of the benefits of

retention/detention basins and how their implementation in the English River Watershed would

serve a community. Also provide in Appendix A.2 of this report are the details of a generic

detention basin design, including costs of materials. In conjunction with built structures for the

reduction of runoff, certain environmental methods may also be desirable. The following section

discusses a environmental method of runoff reduction.

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1.3.2 Environmental Rehabilitation:

Riparian buffer strips are engineered areas of vegetation at the interface between rivers and land.

Buffer strips are usually designed to reduce pollution from runoff into rivers and streams. This

reduction in pollution increases river water quality, which benefits wildlife and reduces the

chemical demand required for municipal drinking water treatment. Buffer strips also look

natural because they use native tree and bush species. This makes buffer strips very aesthetically

pleasing to both humans and wildlife. The use of vegetation slows down runoff flows in the

attempt to infiltrate as much of the water as possible while also reducing pollutant transport. The

roots of these plants prevent erosion of topsoil and the selected vegetation is also required to be

hydrophilic (water loving) due to expected submergence during high flow events. The general

layout of a riparian buffer strip is shown in Figure 10.

Figure 10: Example of Riparian Buffer Strip Layout (Hill, 2009)

An example of the successful use of riparian buffer strips to promote water quality is in

Baltimore County, Maryland. Baltimore has three drinking water reservoirs in Baltimore County

which provide water to about 1.6 million people every day (Stabenfeldt, 1996). In the early

ed to protect their water resources and implemented the

following strategies: watershed management and planning, water quality monitoring, citizen

education, volunteer stream restoration activities, and legislation. This project was supported by

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a $24 million funding program to improve streams, create wetlands and forests. The integral

nature of riparian buffer strips to their water management plan is exemplified by the following

quote from their Regulations for the Protection of Water Quality, Streams, Wetlands and

F loodplains:

The purpose of the Forest Buffer is to protect Baltimore County's streams, wetlands and f loodplains; to protect the water quality of Baltimore County's watercourses, reservoirs, lakes and the Chesapeake Bay; to protect Baltimore County's riparian and aquatic ecosystems; and to provide environmentally sound use of Baltimore

(Stabenfeldt, 1996)

A major concern addressed with this regulation was building new forest buffer in areas where

channel erosion, stream pollution or habitat degradation exists. Implementation of the forest

buffers also helped Baltimore County reduce their peak runoff volume. Anvil Engineering

decided to include this discussion of environmental rehabilitation with the use of riparian buffer

strips due to the importance of runoff mitigation to the reduction of peak flows in the English

River Watershed.

It was hypothesized that with the larger percentage of agricultural land within the watershed,

river flows may be significantly affected by the implementation of riparian buffer strips. From

Table 1, about 59 percent of the English River watershed is cultivated cropland. Cropland is

known to cause more precipitation to become runoff contributing to larger stream flows than

similar land used a forest (Mays, 2005). Additionally farming practices in the English River

watershed compound the runoff effect by clearing the land of its natural vegetation all the way

up to the river or stream bank. This effectively allows the accumulated runoff from a large area

of farm land to dump directly into streams and rivers, causing river bank erosion, pollution, and

flooding. Riparian buffer strips attempt to solve this issue by providing a region of natural

vegetation prior to the river or stream to slow the water down and potentially infiltrate it into the

ground.

In order to determine how much of this cropland would need to be converted to riparian buffer

land, the NRCS Curve Number runoff method was used (Mays, 2005). For information on the

use this method or for the curve number values used please refer to Appendix A.3. Using a 100-

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year 24-hour rainfall event of 6.7 inches, the current land use produces 4.74 inches of runoff.

Assuming riparian buffers replace a sufficient are of cultivated cropland to achieve a 5%

reduction in runoff volume, about 50 square miles (~32,000 acres) of cultivated cropland would

need to be converted. This result means that if the banks of the English River consisted entirely

of cropland, converting to 100 foot wide buffer strips on both banks would require 1,300 miles of

buffer on each side of the river. This number greatly exceeds the length of the river, but

considering 50 square miles is only 8% of the watershed that is currently consists mainly of

cultivated cropland, the use of engineered wetlands or wider buffer strips is still a viable option.

Other benefits of the use of rehabilitated wetland areas include: interception of excess nutrients

such as nitrogen and phosphorus and preservation of biodiversity. Nutrients are harmful to water

quality due to the increased production of algae within waterways which contribute to

Reducing nutrient loading increases river water

quality and has the potential to decrease water treatment plant operating expenses. A summary

of benefits according to the National Resource Conservation Service include: remove up to 60%

or more of certain pathogens, remove up to 75% or more of sediment, control soil erosion by

both wind and water, improve soil quality, enhance fish and wildlife habitat, protect buildings

and crops, and conserve biodiversity (NRCS).

An always important factor to consider is potential funding sources that are available to help

build riparian buffer strips. The Conservation Reserve Program gives technical and financial

assistance to eligible farmers for building riparian buffers. Funding includes a cash match and

annual rental payment for building the buffer on their land. The Environmental Quality

Incentives Program also gives technical and financial assistance to agricultural producers similar

to the Conservation Reserve Program. Other programs do exist and are usually intended to

improve soil quality, water quality, and habitat production. The majority involve a cash match of

50-75% by the farmer, with annual payments to the farmer

land (NRCS).

Environmental rehabilitation remains a viable option for the English River Watershed and

realistically a combination of built structures and rehabilitation is the most likely solution for any

watershed management plan. The next section begins a discussion of local solutions for Kalona.

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2.0: T ASK 2 Preliminary Design A lternatives for C reek Improvements

Task 2 is the creation of two

west extent, which is called the west creek throughout this report. The reasons for the focus on

the improvement of the west creek are: the amount of the flooding characterized by the most

recent FEMA flood plain map associated to the west creek (orange shaded area of Figure 11), as

well as the general disrepair and property-encroaching bank erosion of the west creek (Figure 12

and Figure 13). These reasons set the goals for the two preliminary designs; increase the water

conveyance through the west creek and mitigate future bank erosion. The selection criteria in

Section 2.4 incorporate these goals in addition to the projected alternative cost, rated level of

protection, and other factors.

The two design alternatives chosen by Anvil Engineering were: Alternative 1 Bank

Stabilization; the use of gabion boxes and riprap (effectively channelizing the creek by lining it

with rocks), and Alternative 2 Bank Stabilization with a Detention Basin; using the same rock

lining as previously mentioned with the addition of a detention basin north of Kalona to mitigate

peak flow events. By lining the west creek with rocks the roughness of the channel can be

reduced; thereby increasing the ability of the creek to convey higher flows. Additionally, the use

of appropriately sized rocks and installation procedures will also protect the banks from erosion.

The incorporation of a detention basin in the second alternative is to increase the level of

protection of the design by delaying high runoff flows in the upper basin. This delay then

minimizes the peak flows experienced downstream and reduces the risk of out of bank events

along the west creek.

Alternative 1; the use of bank stabilization alone, is recommended by Anvil Engineering.

Before discussing the details of each design alternative the objectives for their preliminary

design as laid out by the client in the request for proposal will be reiterated to again establish the

scope of work.

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Figure 11: Shaded areas indicate those regions affected by 100-year events in the English River and its tributaries. The extent of flooding of west creek during a 100-year event is the orange shaded area. (Strategic Alliance for Risk

Reduction (STARR), 2010)

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Figure 12: Two views of the west creek. a.) Looking south or downstream, north of the US Highway 22 bridge. This picture shows the depth and shape of the channel as well as the slump of top soil into the channel due to extensive bank erosion. b.) Looking south or downstream on the B Avenue bridge towards the C

Avenue bridge. In this picture the riprap placed at the outlet of the bridge to minimize scour can be seen slumping into the channel.

a. b.

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Figure 13: Two views of the west creek exemplifying the amount of erosion and disrepair. a.) View of the right bank of the west creek looking downstream, north of the US Highway 22 bridge. The photo shows the sheared top soil indicative of bank erosion along a stretch of residential back yards. b.) A view of the

south side of the C Avenues bridge/culvert. The right bank culvert is partially filled with sediment impeding its ability to convey water in the west creek.

a. b.

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2.1: Design Objectives

Listed below are the design objectives for the preliminary design of improvements to the West

Creek. Each objective was taken from the request for proposal with clarifications solicited

during subsequent meetings with the client throughout the project. The objectives are

summarized below with a brief discussion of how each was accomplished by Anvil Engineering.

2.1.1 C lient Contact:

Regularly scheduled meetings and weekly progress reports were required by the client for the

duration of the English River Watershed project. Anvil Engineering fully supports strong lines

of communication with clients and views it as a necessity for the successful completion of the

project. In keeping with this ideal, Anvil submitted reports no later than 4:00pm on each Friday

during the project and attended many meetings with Professor Larry Weber to review the status

and direction of the English River Watershed project.

2.1.2 Regulations/Permits:

The regulations of any involved agency, such as the Iowa DNR, Washington County, and the

City of Kalona, were reviewed in order to design improvements to the west creek that do not

conflict with any codes or regulations. Some of the design manuals and permitting reviewed

were the Iowa Stormwater Management Manual, the Iowa Statewide Urban Designs and

Specifications (SUDAS), and the Iowa Department of Natural Resources National Pollution

Discharge Elimination System (NPDES) permits. Appendix B.4.1 contains a discussion of

permitting.

2.1.3 Design A lternatives:

Two design alternatives were investigated for Task 2 of this project. The two alternatives; bank

stabilization of the creek and bank stabilization with an upstream detention basin were chosen

over other options (such as dredging, levees, and diversion of flow to other creek systems) due to

their feasibility and long term benefit; for instance the prevention of further bank erosion into

residential zones and the decreased maintenance cost due to not having to dredge at a more

frequent interval.

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2.1.4 Utilities:

Any utility locations affected by each design alternative was reviewed and noted. These utilities

were mostly the bridges and stormwater outfalls related to the creek. Utility rerouting and

redesign is outside the scope of this project.

2.1.5 Stormwater M anagement:

Each option was designed according to the guidelines laid out in the Iowa Stormwater

Management Manual. For example, the design of an open channel with a majority of drainage

area consisting of open land requires the use of the Natural Resources Conservation Service

(NRCS) curve number method for the determination of runoff flows and the use of the WinTR-

55 program discussed further in Appendix B.1 of this report

2.1.6 Construction:

A brief discussion of preliminary construction phase sequencing was addressed for the selected

alternative. In short the design and construction of Alternative 1 would most likely be able to be

completed within a year. This timeline estimate is subject to change due to the possibility of

unforeseen factors such as the conditions of the bridges and storm sewers. It should be noted

that detailed construction plans are outside the scope of work for this preliminary design project

and have not be generated.

2.1.7 Drawings and Budgets:

Preliminary sketches of lined cross-sections for Alternative 1 were created. The drawings are

detailed sufficiently to show the potential design, but not for actual construction. Cost estimates

for each alternative have also been created and justified using available cost estimates from

contractors or other external consultants. To estimate labor costs, material costs were multiplied

by a factor of 1.5 and summed with the original material costs.

The following sections detail each design alternatives beginning with a discussion of those

attributes shared by both alternatives.

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2.2: A lternative Solutions

The west creek is currently an earthen channel that has shallow side slopes (slope of the banks)

north and south of Kalona, with steeper side slopes where the creek passes within the city limits.

The last known maintenance performed on the channel was a dredging operation in 1994.

Subsequently, due to heavy rainfalls causing the high flows necessary for erosion, the channel

ts (Figure 12). For modeling

purposes,

calculate the flow in open channels, such as the west creek (Mays, 2005). The use of the

The goals of the two alternatives are therefore flood mitigation and erosion control. The basic

thrust of the plan is to .

This reduction in resistance would be accomplished by shaping and lining the banks with rock.

As mentioned previously the current roughness of the creek is 0.050. By lining the channel with

stone this roughness can be reduced in half to 0.025. This reduction effectively doubles the

amount of water the west creek is able to convey. By conveying more water the creek is then

able to stay within its banks at flows that would otherwise cause flooding without the lining. The

the improvements suggested by each design alternative to determine the storm return period

-of- t. An out-of-bank

event for the analysis is defined as the flow that creates a water level within the west creek that is

at least two feet above the either the left or right bank (whichever is greater). The models were

run to simulate two scenarios for the three cases: the current condition of the west creek and for

each alternative. The two scenarios were: a storm event with the English River at normal flows

and a storm event with the English River at 100-year flood levels (Table 3). As expected when

modeling the storm events with the English River at a 100-year flood level the southern extent of

the west creek was entirely flooded. In each of the 100-year flood scenarios the storm event that

caused an out-of-bank event in the west creek occurred at relatively low flows that were not

affected by backwater effects from the English River. Therefore the storm return period that

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would cause an out-of-bank event for the two scenarios was similar for each case. The results of

the modeling analysis are presented in Table 3 and represent the level of flood protection

provided by each design alternative. In addition to lower th

lining provides bank stabilization. Stabilization of the banks prevents erosion.

The first alternative is the use of the stone lining only. The second alternative incorporates the

rock lining designed for the first alternative with a dry detention basin situated north of Kalona.

A dry detention basin is a designated floodable area designed to temporarily store water during

high flows, releasing the stored water at a controlled rate. For the second alternative the northern

-off during storm events with a return period greater than

2-years and release the detained run-off to the west creek at the 2-year storm event flowrate. The

main advantage of the detention basin is reflected by a higher level of flood protection (Table 3).

Table 3: Results of modeling efforts detailed in Appendix B.1. The west creek in its current condition is able to convey flows from a 2-year return period Type II rain storm in Washington County, Iowa without an out-of-bank event. The design alternatives significantly improve upon the level of conveyance offered by the west creek by

lining the creek with stone. Alternative 2 provides greater protection by the addition of a detention basin.

Another factor in the design of the alternatives was the type of bank stabilization method.

Ideally the easiest method of lining the west creek with rock would be to dump rock on the

banks. This ideal would not be effective for a variety of reasons. The first is the side slope of

many portions of the west creek is too steep to maintain the rock on the banks and out of the

channel. Second, if the slopes were made shallow enough to hold the rock, much of the land

English River - Normal Flow

English River - 100-year Flood

Current Conditions 2-year 2-year

Design Alternative 1 - Bank Stabilization

10-year 10-year

Design Alternative 2 - Bank Stabilization with Detention Basin

50-year 50-year

Cas eSce nario

Rate d Le ve l of Prote ction

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must be of a hearty chemical composition and of sufficient size to prevent the rock from rapidly

eroding or being carried away by swift water velocities at high flows.

Gabion baskets were therefore chosen to overcome the constraints presented by the steep side

slopes and constraints of residential backyards. A gabion basket can be visualized as a

rectangular box with sides made of chain link fence filled with large stones (Figure 14). These

baskets are able to be stacked on top of one another to achieve a side slope of 6 feet vertical for

every 1 foot in the horizontal direction (Iowa SUDAS, 2008). Gabion baskets were therefore

chosen as the lining for portions of the west creek within the city limits. Anvil Engineering also

Figure 14: On the right an example gabion baskets used to stabilize the banks of a stream. On the left, a general schematic for the installation of 6 foot x 3 foot x 3 foot gabion baskets (Iowa SUDAS, 2008).

The lengths of the west creek outside of the city limits were assumed by Anvil Engineering to be

more apt for the use of riprap. Riprap, unlike gabion baskets, is a loose stone lining (Figure 15).

Meaning the stones themselves are not contained within a box, but are instead held by their own

weight against the banks. Because the riprap is loose a constraint on the side slope of the creek

is applied to ensure the stones do not fall into and plug up the channel. The maximum side slope

recommended when using riprap is 1 foot vertical for every 2 feet horizontal; a much shallower

slope then what is permitted for gabion baskets.

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Figure 15: On the right an example of riprap used to stabilze the banks of a lake. On the left, a general schematic for the installation of riprap (Iowa Department of Natural Resources, 2006).

The type of stone material selected for the two methods of bank stabilization are dictated by the

appropriate standards for design. For both methods the material consists of large rock, generally

limestone or quartzite. All stone must be less than 3 feet in the largest dimension (Iowa

Department of Natural Resources, 2006). The typical thickness for a riprap layer is

approximately 2 feet (Van Dyke, 2011). Gabion baskets use stone similar in composition to

riprap but potentially of smaller size; a nominal diameter of approximately six inches (Iowa

SUDAS, 2008). A typical gabion basket is six feet in length by three feet in width and breadth.

The stone lining is preferred over the existing soil due to its strength, energy dissipation, and

ness. The strength and energy dissipation of the stone reduces

higher flows. General schematics of a cross-section lined with riprap and gabion baskets are

shown in Figure 14 and Figure 15, respectively.

The next two sections expand

upon the details of Alternative 1 and 2, respectively, and are followed by a discussion of Anvil

-making process for the selection of Alternative 1 as the

recommended alternative.

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2.2.1: A lternative 1 Bank Stabilization Alternative 1 is the use of riprap and gabion baskets to stabilize the banks of the west creek and

. This stabilization of the creek banks protects the

channel for further erosion during high flow events and increases the conveyance of the channel

stance to flow.

Due to riprap being less expensive than gabion baskets, Anvil Engineering sought to use riprap

on all portions of the channel with sufficiently shallow side slope (2:1 horizontal to vertical) or

where restrictions on expanding the channel to lessen the side slope were not present (i.e. the

channel cannot be widened in areas where the creek is hemmed in by residential property).

Therefore the design for the placement of each bank stabilization method is to use riprap to the

north and south of the Kalona city limits and use gabion baskets within the city. A modified

satellite image to graphically represent the placement of the stabilization methods is shown in

Figure 16. Diagrams depicting the proposed changes to two of the creek cross-sections with

each stabilization method are shown in Figure 17 and Figure 18.

Figure 16: Location of riprap and gabion boxes along the West Creek

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Figure 17: Cross-Section view of Sta. 15234.77. This northern section of the channel has a relatively shallow slope, so the application of riprap is acceptable.

Figure 18: Cross-section view of 6173.22. This is inside the city limits, so the slope is steeper and the width is limited. This is a where the application of gabion boxes is preferred.

The total bank length for the placement of riprap and gabion boxes was 8,032 feet and 4,038 feet,

respectively. This is correlated to roughly 54,000 tons of riprap and 4,600 gabion baskets.

Additionally, an amount of back fill and excavation was assumed for each gabion basket

installed. The total estimated cost for Alternative 1 is $6 million. Calculations to derive the

amount of material, and the total cost of the bank stabilization can be found in Appendix B.2.

Table 4 below is a summary of Alternative 1.

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Table 4: Alternative 1 Summary Table

Tons of riprap 53,800

Length of west creek covered by riprap (ft)

8,032

Number of gabion boxes 4,576

Tons of stone for gabion boxes

15,000

Length of west creek covered by gabion boxes (ft)

4,038

Total Cost $6,000,000

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2.2.2: A lternative 2 Bank Stabilization with Detention Pond

Alternative 2 is a combines all of the bank stabilization of Alternative 1 with a detention pond

north of Kalona. The detention pond is designed to hold in abeyance runoff flows up to 1,000

cubic feet per second (cfs) and release this ponded water at a rate of 450 cfs. The area required

to hold this the design flow, assuming a depth within the detention pond of 10 feet, is

approximately 297,000 square feet (~6.82 acres). The detention pond location was chosen north

of Kalona to detain runoff flows from the upper basin of the west creek watershed. This would

then allow the runoff flows from the southern areas of the west creek basin to accumulate and

flow out of the creek without combining with high runoff flows from the north; thereby reducing

the risk of flooding. Calculations used for sizing the detention basin are in Appendix B.3. A

potential location for the detention pond is shown in Figure 19. At this location the emergency

spillway was designed on the west side of the pond to protect Maple Avenue and any nearby

residential property from the effects of erosion caused by the potential high flows expected to

occur if the spillway is utilized. The method used to design the detention basin was proscribed

by the American Association of State Highway and Transportation Officials (AASHTO). The

total cost for Alternative 2 is $7.5 million. Table 5 is a summary of Alternative 2.

Figure 19: The location of the detention north of the City of Kalona, just West of Maple Avenue. The reasoning of the location is described in Section 2.2.2

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Table 5: Alternative 2 Summary Table

Detention Basin Design Inflow (cfs)

1,000

Detention Basin Design Outflow (cfs)

450

Detention Basin Volume (ft3)

2,970,000

Detention Basin Total Depth (ft)

15

Detention Basin Surface Area (acres)

7


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2.3: Selection C riter ia and Weighting Factors

In order to select between the two preliminary design alternatives a set of selection criteria was

developed. These criteria were then assigned a weight by their importance to the client. The six

selection criteria and their associated weighting factors are listed below with brief discussions.

In each case the alternatives were first ranked against each other with the more desirable of the

alternatives receiving a rank of two. This rank is then ng

factor and the product of rank and weighting factor is summed for each alternative. The selection

process is graphically represented in the following section with the use of a matrix.

Selection Criteria

Cost The estimated cost of the design. Cost is the most important of the criteria for this project and therefore receives a weighting factor of five.

Level of Protection The storm return period that causes an out-of-bank condition for the west creek. This was determined by WinTR-55 and HEC-RAS model simulations for both alternatives. This criterion also takes into account the expected protection against erosion provided by each alternative. This criterion is of less importance than cost, but is also the purpose of the design and is therefore given a weighting factor of four.

Expected Land Use The amount of land required to construct each alternative. It is expected that Alternative 2 will require more land due to the construction of a detention pond. More land use requires more money in order to purchase the land; therefore, this criterion is given a weighting factor of three.

Operation and Maintenance (O&M) Costs associated with the maintenance of each alternative. These include dredging, inspections, and replacement. A weighting factor of four is assigned to this criterion due to the significance of O&M costs to the life-cycle of the design.

Ability to Upgrade This criterion establishes the ease with which each alternative may be redesigned or upgraded in the future to handle higher flows due to additional development in Kalona. Due to the uncertainty in estimating this criterion a weighting factor of two is assigned.

Construction Time The length of time required to construct each alternative. The shorter the time of construction the fewer disturbances to the flow of commerce within the city; therefore, it is desirable to have a shorter construction time. Again due to uncertainty in the estimate a weighting factor of two is assigned.

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2.4: Selection Matrix

Criterion Alternative 1 Alternative 2

Rank Weight Product Rank Weight Product

Cost 2 5 10 1 5 5

Level of Protection 1 4 4 2 4 8

Expected Land Use 2 3 6 1 3 3

O&M 2 4 8 1 4 4

Ability to Upgrade 2 2 4 1 2 2

Construction Time 2 2 4 1 2 2

Sum Total 36 Sum Total 24

As explained in the previous section; for each of the criterion the Alternatives were first ranked

against each other with the more favorable of the two alternatives

instance Alternative 1 estimated costs were $6 million and Alternative 2 estimated costs were

$7.5

this rank is multiplied by the cost

multiplication of the ranks and weights are then summed to give the overall score for the

alternatives. The alternative with the greater score was then selected as the recommended

alternative. Anvil Engineering recommends the selection of Alternative 1. The following

section is a summary of design Task 2.

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2.5: Summary of Task 2 Design

The objective of design Task 2 was to develop preliminary designs for the improvement of

reek. The current problems facing the west creek can be concisely expressed as

extensive erosion and frequent flooding. To address these problems Anvil developed two

alternatives: Alternative 1 was the use of two bank stabilization techniques to prevent future

After detailing the preliminary designs for both Alternatives and computing rough cost estimates,

Alternative 1 was chosen as the recommended design.

Alternative 1 uses gabion baskets and riprap to shore up the banks of the west creek. This then

prevent soil from washing into the creek during high flow events. The stabilization of the bank

becomes more able to convey high flows that may have caused an out-of-bank event if the

channel were left in its current state. The cost of Alternative 1 is roughly $6 million.

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3.0: T ASK 3 F E M A M ap Analysis

With the issuance of new flood plain maps by FEMA, a vast majority of the City of Kalona was

mapped into the high-risk or 100-year flood plain zone. This zone is denoted as Zone A and is

the blue shaded area in Figure 20. Due to this mapping the homes inside of the high-risk flood

zone will experience additional financial burdens by the need to buy flood insurance.

Figure 20: Map of Kalona, Iowa overlaid by the new FEMA 100-year flood plain delineations. As can be seen a majority of the city now lies within Zone A (the 100-year flood plain)

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Anvil Engineering, in an effort to help the residents of Kalona interpret Figure 20 in relation to

the National Flood Insurance Program (NFIP) guidelines for flood insurance, developed Table 6

and its associated Figure 21. This figure has each parcel in the corporate limits of Kalona color

coded by the status of parcel in relation to the flood plain. For instance dark green parcels are

not in the flood plain; whereas dark red parcels lie entirely in the flood plain. Parcels hashed

with black lines are partially in the flood plain. These partially covered parcels were broken in

smaller subgroups based on whether the structures on that parcel were in the flood plain (red),

partially in the flood plain (yellow), or not in the flood plain (green). This method of color

coding was used specifically to coincide with FEMA letter of map amendment (LOMA)

procedures. A LOMA allows a homeowner to apply for a change in flood-risk status with

FEMA. In order to qualify for a LOMA or LOMA Out as Shown a homeowner has to provide

plain or that the home is explicitly shown as not in the flood plain by using the flood plain maps

provided by FEMA. Therefore the parcels partially in the flood plain that are coded green are

eligible for a LOMA Out as Shown, and those parcels partially in the flood plain that are coded

yellow may benefit by hiring a survey team to determine the lowest adjacent grade of their home.

It is not able to be determined whether parcels coded red with black hashing would benefit

pursuing a LOMA. Table 6 is an effort to quantify monetarily the assets within each category

represented in Figure 21.

Table 6: A quantitative breakdown of Figure 21, including the total FY10 assessed property values, obtained from the Washington County Office, which are affected by each parcel category. The monetary values in the

third column are in millions of dollars.

Number of Parcels in Category

Total Property Value in Category

($1,000,000)391 44.3$ 10 2.6$ 70 10.5$ 84 14.2$ 555 78.7$ 43 0.9$

Parcel Partially in Flood Plain, Structure partially in Flood PlainParcel Partially in Flood Plain, Structure out as shown

Parcel not in Flood PlainParcel Partially in Flood Plain, No structure on parcel

Category

Parcel in Flood PlainParcel Partially in Flood Plain, Entire Structure in Flood Plain

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Figure 21: Parcel map of the corporate limits of Kalona, Iowa color coded to express the impact of the new FEMA flood map. It is hoped that residents can utilize this map to help determine what options are available to them for designating their home either in the high-risk flood plain (Zone A) or outside of the high-risk flood plain (Zone X). Those parcels not in the flood plain are automatically in Zone X. Those parcels partially in the flood plain may be designated as in Zone A. These homeowners may be able to have their property reclassified by submitting a letter of map amendment (LOMA). The parcels with black line hashing are partially in the flood plain; of these parcels those colored green are eligible for a LOMA out as shown, and those colored yellow, by hiring a survey crew,

may qualify for a LOMA. The parcels in red are either entirely in the flood plain or have the entire structure on the parcel in the flood plain. It cannot be determined whether these parcels would benefit by pursuing a LOMA.

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4.0: About A nvil E ngineer ing Anvil Engineering, a design engineering firm located in Iowa City, Iowa, specializes in water

resource management, water quality protection, transportation construction, and structural design

with a focus on client satisfaction, economics, and sustainability.

and exceptional solutions to a wide range of civil and environmental engineering needs. We aim

to meet the goals of our clients and maintain a mindset for sustainability in or

The following is a brief summary of the Anvil Engineering design team; resumes for each

individual are located in Appendix D.

M atthew Anderson: Structural Transportation Specialist.

Matthew has been involved with numerous transportation projects which include

inspection of the Fort Madison, Iowa, bypass and the Farmington, Iowa, Des

Moines River bridge.

Jonathan Durst : Project Manager / Water Resources Specialist.

Jon has worked on flood mitigation projects for the Cedar Rapids, Iowa, Quaker

Oats facility and Coralville, Iowa, Iowa River Landing development.

Jacob Ehrmann: Structural Engineer.

Jacob has experience with the inspection of numerous bridges along Highway 61

in Fort Madison, Iowa.

John Foster: Water Quality Specialist.

John has worked extensively with remote water quality sensor networks in the

Clear Creek watershed in Coralville, Iowa.

Ian Stewart: Environmental Remediation and Control Engineer.

Ian has worked alongside the Iowa Department of Natural Resources and Cargill

of Sioux City, Iowa, to develop plans for enhanced waste management and

minimization.

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5.0: Project Summary

Anvil Engineering, a small engineering firm based out of Iowa City, Iowa, has been contracted to

complete three preliminary design tasks for an English River Watershed Plan at the behest of

Kalona, Iowa. Anvil

approach was an ideal match for the assignment of this project.

The three design task; characterization of the English River Watershed, two preliminary designs

for improvements to Kalona

were all completed on schedule. The characterization of the watershed and analysis of the flood

map culminated in Section 1 and 3 of this report as references for technical information.

Information such as the 100-year river flows and number of parcels eligible for risk

reclassification within the National Flood Insurance Program. Task 2 detailed in Section 2

creek. The

cost estimate for this preliminary design solution was $6 million.

The estimated total cost of the English River Watershed Plan is $42,500. This amount was

derived by computing Anvil Engineering hourly rates for a 10 hour work week throughout the 13

week duration of the project for the 5 person design team.

Anvil Engineering looks forward to providing continued engineering excellence and customer

satisfaction as we move forward with the English River Watershed project.

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6.0 References

Iowa Stormwater Management. (2009). Retrieved April 14, 2011, from Iowa State University Institute for Transportation: /www.intrans.iastate.edu/pubs/stormwater/Design/2C/2C-‐9 Detention Storage Design.pdf

2009 Annual Report. (2010, June 29). Retrieved March 27, 2011, from Iowa Department of Agriculture and Land Stewardship: http://www.agriculture.state.ia.us/IWIRB.asp

Coralville Lake Fact Sheet. (2010, August). Retrieved April 2, 2011, from U.S. Army Corps of Engineers: http://www.mvr.usace.army.mil/Brochures/documents/CoralvilleLakeFactSheet.pdf

2010 Annual Report. (2011, February 25). Retrieved March 27, 2011, from Iowa Department of Agriculture and Land Stewardship: http://www.agriculture.state.ia.us/IWIRB.asp.

Iowa Department of Agriculture and Land Stewardship: FAQ. (2011, March 27). Retrieved March 27, 2011, from http://www.agriculture.state.ia.us/IWIRB.asp

Cherry Hills Inc. (2009). Cherry Hills Construction and Demolition Inc. Retrieved April 25, 2011, from http://www.cherryhillinc.com/

Chin, D. A. (2006). Water-‐Resources Engineering. Pearson Education, Inc.

FEMA. (2011, March 3). Kalona, Iowa Stakeholder Meeting. (Anvil Engineering, Interviewer) Kalona, Iowa.

Geology.com. (2011). Iowa Lakes, Rivers, and Water Resources. Retrieved February 13, 2011, from Geology.com: http://geology.com/lakes-‐rivers-‐water/iowa.shtml

Hill, D. (2009). Riparian Buffer Strips. Lexington, Kentucky, United States.

Iowa Department of Natural Resources. (2006). How to Control Streambank Erosion. Iowa, United States.

Iowa Department of Transportation. (2011). Storm Water Discharge Permits. In IA DoT Office of Design, Design Manual (pp. 10D-‐1 page 4).

Iowa DNR. (2009, May 8). Watershed Boundary of the English River in Iowa, from its Confluence with the Iowa River, Derived from the Watershed Boundary Dataset. Retrieved March 1, 2011, from University of Iowa GIS Library: ftp://ftp.igsb.uiowa.edu/GIS_library/Watersheds/Stream_Watersheds/Mississippi_River/Iowa_River/English_River/

Iowa Flood Center. (2011, February 13). Drainage Map: English River. Retrieved February 13, 2011, from Iowa Flood Center Maps: http://weather.iihr.uiowa.edu/ifc/drainage.html

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Iowa SUDAS. (2008). SUDAS Standard Specifications -‐ Section 9050 -‐ Gabions and Rip Rap. In I. f. University, Iowa Statewide Urban Designs and Specifications (SUDAS).

Mays, L. W. (2005). Water Resources Engineering. John Wiley & Sons, Inc.

Midwestern Culvert Design, L. (2011, April 25). (A. Engineering, Interviewer)

Northern Iowa Construction Products. (2011, April 23). (A. Engineering, Interviewer)

NRCS. (n.d.). Buffer Strips: Common Sense Conservation. Retrieved 2011, from National Resource Convervastion Service: http://www.nrcs.usda.gov/feature/buffers/*

Stabenfeldt, L. (1996). Forest and Riparian Buffer Conservation. Retrieved from Chesapeake Bay Program: http://www.chesapeakebay.net/archive/facts/forests/farbc/farbc-‐00.htm

Strategic Alliance for Risk Reduction (STARR). (2010, June). Preliminary Engineering Flood Study.

U.S. Army Corps of Engineers (USACE). (2010). HEC-‐RAS User's Manual. Davis.

U.S. Census Bureau. (2011, March 26). 2010 Census Data. Retrieved March 26, 2010, from 2010 Census: http://2010.census.gov/2010census/data/

USDA. (2009). WinTR-‐55. Retrieved April 13, 2011, from WinTR-‐55 User's Guide: http://www.wsi.nrcs.usda.gov/products/W2Q/H&H/docs/WinTR55/WinTR-‐55%20User%20Guide.pdf

USGS. (2010, November). USGS Surface Water for Iowa: Peak Streamflow. Retrieved February 13, 2011, from USGS National Water Information System: http://nwis.waterdata.usgs.gov/ia/nwis/peak/?site_no=05455500&agency_cd=USGS

Van Dyke, M. (2011, April 25). P.E. (A. Engineering, Interviewer)

Wikipedia. (2010, December 4). Kalona, Iowa. Retrieved February 13, 2011, from Wikipedia: http://en.wikipedia.org/wiki/Kalona,_Iowa

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Appendix A : Task 1 Supplemental Information

A .1: Descr iption of land use categories

Land Use Descriptions:

Open Water - All areas of open water, generally with less than 25% cover of vegetation

or soil.

Developed, Open Space - Includes areas with a mixture of some constructed materials,

but mostly vegetation in the form of lawn grasses. Impervious surfaces account for less

than 20 percent of total cover. These areas most commonly include large-lot single-

family housing units, parks, golf courses, and vegetation planted in developed settings for

recreation, erosion control, or aesthetic purposes

Developed, Low Intensity - Includes areas with a mixture of constructed materials and

vegetation. Impervious surfaces account for 20-49 percent of total cover. These areas

most commonly include single-family housing units.

Developed, Medium Intensity - Includes areas with a mixture of constructed materials

and vegetation. Impervious surfaces account for 50-79 percent of the total cover. These

areas most commonly include single-family housing units.

Developed, High Intensity - Includes highly developed areas where people reside or work

in high numbers. Examples include apartment complexes, row houses and

commercial/industrial. Impervious surfaces account for 80 to100 percent of the total

cover.

Barren Land (Rock/Sand/Clay) - Barren areas of bedrock, desert pavement, scarps, talus,

slides, volcanic material, glacial debris, sand dunes, strip mines, gravel pits and other

accumulations of earthen material. Generally, vegetation accounts for less than 15% of

total cover.

Deciduous Forest - Areas dominated by trees generally greater than 5 meters tall, and

greater than 20% of total vegetation cover. More than 75 percent of the tree species shed

foliage simultaneously in response to seasonal change.

4/30/2011



Evergreen Forest - Areas dominated by trees generally greater than 5 meters tall, and

greater than 20% of total vegetation cover. More than 75 percent of the tree species

maintain their leaves all year. Canopy is never without green foliage.

Grassland/Herbaceous - Areas dominated by grammanoid or herbaceous vegetation,

generally greater than 80% of total vegetation. These areas are not subject to intensive

management such as tilling, but can be utilized for grazing.

Pasture/Hay - Areas of grasses, legumes, or grass-legume mixtures planted for livestock

grazing or the production of seed or hay crops, typically on a perennial cycle. Pasture/hay

vegetation accounts for greater than 20 percent of total vegetation.

Cultivated Crops - Areas used for the production of annual crops, such as corn, soybeans,

vegetables, tobacco, and cotton, and also perennial woody crops such as orchards and

vineyards. Crop vegetation accounts for greater than 20 percent of total vegetation. This

class also includes all land being actively tilled.

Woody Wetlands - Areas where forest or shrubland vegetation accounts for greater than

20 percent of vegetative cover and the soil or substrate is periodically saturated with or

covered with water.

Emergent Herbaceous Wetlands - Areas where perennial herbaceous vegetation accounts

for greater than 80 percent of vegetative cover and the soil or substrate is periodically

saturated with or covered with water.

4/30/2011



A .2: Hypothetical Reservoir System Design & Cost

In the initial stages of designing a detention basin the main focus is determining the required size

of the basin. The classic detention sizing procedure consists of the following steps (Mays, 2005):

1) Estimate the preliminary storage volume Vs.

2) Use site topography to prepare a preliminary layout of a detention basin that has the desired volume and outlet configuration.

3) Determine stage-storage-outflow characteristics of the trial pond size.

4) Perform routing of the input hydrographs through the pond. Steps 3 and 4 can be accomplished using computer models.

5) If the trial pond does not meet design criteria and goals, resize the basin and or reconfigure the outlet(s) and repeat steps 3 5 until the goals and criteria are met.

Because a trial pond has not been constructed and tested, steps 3 5 will not be discussed any

further in this report but additional information can be obtained from Water-Resources

Engineering by Larry W. Mays.

To visually understand what effect a detention basin has during a flood or peak flow event,

Figure 22 has been included. In viewing this figure it can be seen that the peak flow is reduced

and discharge slowly over time. The volume of storage Vs can also be visualized from this

figure. However, because the flow in this figure is hypothetical, the volume of storage cannot be

calculated using this figure. There are many ways to initially determine the volume of storage but

the American Association of State Highway Transportation Officials (AASHTO) (1991)

recommended using a triangular-shaped inflow and outflow hydrographs to determine a

preliminary estimate for Vs. (Chin, 2006) the recommended triangular-shaped inflow and

outflow hydrograph can be viewed below as Figure 23.

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Figure 22: Detention Storage Volume Vs (Mays, 2005).

Figure 23: Inflow and Outflow hydrographs for AASHTO (1991) procedure (Mays, 2005).

4/30/2011



Assume tb = 12 hours

Goal, 5% reduction of flow; thus, 30,000(0.95) = 28,500 cfs

Or

*The volume of an acre-foot can be described as one acre of land one foot deep.

The two of the most prevalent material costs in the construction of a basin are those associated with the excavation of soil and the purchase of concrete. Estimates for these costs were obtained to help develop some base costs for a basin of this size. First, it is assumed that the hypothetical basin requires only a small fraction (a hundredth) of its entire volume to be excavated due to the placement of the basin in an ideal region that can store the water between the existing ridges of land.

*$2.50/yd3 of excavated dirt obtained from Steger Construction Inc.

Concrete costs for this hypothetical basin will also be taken as a fracvolume. Typically only areas related to flow control structures require the use of concrete; therefore the fraction chosen is one thousandth of the total basin volume.

*$400/yd3 of concrete obtained from Environmental Design class notes, Professor Gene Parkin.

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A .3: Hypothetical Riparian Rehabilitation Design & Cost

The NRCS curve number method from (Mays, 2005) assigns a curve number to a type of land

use. This curve number is meant to show how much rainfall will runoff in this area. A higher

curve number correlates to an area that will have a high percentage of rainfall runoff. The lower

the curve number, the more the water infiltrates the ground and therefore reduces runoff. The

following equations were used for calculating the direct runoff volume.

Potential Maximum Storage:

S = 10 (8.6.6)

(Where CN is the Composite Curve Number from (Mays, 2005))

Direct Runoff Volume:

Pe = (8.6.5)

(Where P is the Precipitation event in inches (Mays, 2005))

According to Professor Allen Bradley from the University of Iowa, College of Engineering,

reducing the direct runoff from the 100-year 24-hour storm event by 5%, will give the

approximate area required to reduce the 100 year storm flood flow by 5%. The following tables

use equations 8.6.6 and 8.6.5 and curve numbers from (Mays, 2005) to compute the area to

reduce the runoff volume by 5%.

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Table 7: Current land use runoff volume

Land Use % of Watershed C N for Soil G roup C W eighted C N

Open Water 0.15 100 0.15 Developed, Open Space 4.57 74 3.38 Developed, Low Intensity 1.59 79 1.26 Developed, Medium Intensity 0.14 86 0.12 Developed, High Intensity 0.03 90 0.03 Barren Land 0.02 50 0.01 Deciduous Forest 3.92 76 2.98 Evergreen Forest 0.01 76 0.01 Grassland 12.6 76 9.58 Pasture/Hay 16.97 76 12.90 Cultivated Cropland 58.33 88 51.33 Woody Wetlands 1.4 70 0.98 Emergent Wetlands 0.28 70 0.20

Composite CN (II) 82.91

S = 2.06 Design P = 6.7 inches Pe = 4.74 inches 5% Peak Reduction = 4.499

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Table 8: Runoff Volume for 5% Peak Reduction Using Riparian Buffers

Land Use % of Watershed C N for Soil G roup C W eighted C N

Open Water 0.15 100 0.15 Developed, Open Space 4.57 74 3.38 Developed, Low Intensity 1.59 79 1.26 Developed, Medium Intensity 0.14 86 0.12 Developed, High Intensity 0.03 90 0.03 Barren Land 0.02 50 0.01 Deciduous Forest 3.92 76 2.98 Evergreen Forest 0.01 76 0.01 Grassland 12.6 76 9.58 Pasture/Hay 16.97 76 12.90 Cultivated Cropland 50.6 88 44.53 Woody Wetlands 1.4 70 0.98 Emergent Wetlands 0.28 70 0.20 Riparian Buffer 7.73 60 4.64

Composite CN (II) 80.75

S = 2.38 Design P = 6.7 inches Pe = 4.499 inches

Because the watershed is 640 mi2, the required area is .0773 x 640 = 49.47 mi2

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Appendix B: Task 2 Supplemental Information

B .1: Data Sets and Models

The purpose of this appendix is to explain how Anvil Engineering obtained and analyzed the

numerous data sets and utilized various computer programs to generate the necessary

information for the design improvements of The primary data sets used

were: Light Detection And Ranging (LiDAR) elevation data of the English River Watershed

provided by IIHR Hydroscience and Engineering: Iowa Flood Center; watershed land use data

(see Figure 4); and the U.S. Geological Survey (USGS) river gage data presented in Section 1.2.

The primary programs used for analysis were: the U.S. Department of Agriculture (USDA):

Natural Resources Conservation Service (NRCS) WinTR-55 program to compute creek flows

during different storm events, and the U.S. Army Corps of Engineers: Hydrologic Engineering

Centers River Analysis System (HEC- RAS) to model the west creek at the different flow

conditions derived from the WinTR-55 program. The HEC-RAS model used by the Anvil

Engineering team was provided by Mr. Scott Ralston, P.E., Flood Plain Mapping Coordinator for

the Iowa Department of Natural Resources (IDNR). The HEC-RAS model was generated by a

group of firms known as STARR (Strategic Alliance for Risk Reduction) under contract with

FEMA.

First to be discussed will be the WinTR-55 model, followed by a discussion of the HEC-RAS

model. For the sake of brevity, much of the technical definitions will have sources cited for

those inclined to read further.

B.1.1: WinTR-55 West Creek Flows

The background information on the WinTR-55 program presented in this section is derived from

the WinTR- lable via the USDA website that has been cited in the

references section of this report (Section 6.0).

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The WinTR-55 program is

used to generate

hydrographs (graphs of flow

vs. time during a rain event)

in small watersheds. A

small watershed, as defined

by

manual, is an area of 1 acre

to 25 square miles. The

drainage area for the west

creek is roughly 3.5 square

miles or 2,240 acres. The

following will discuss the

methodology used to

develop the WinTR-55

model for the west creek.

The first step was to define

the drainage area of the west

creek. The simplest method

of analyzing the effects of

various rain events in the

basin would be to take the

entire drainage area as a

homogeneous whole.

Instead, in the interest of

accuracy, the drainage area

was divided into five smaller

sub-areas and the creek itself

was divided into two reaches

(Figure 24). The reason for

Figure 24: In order to effectively use WinTR-55 the west creek drainage area needed to be defined. The shown breakdown of the drainage area into five sub-areas and the creek into two reaches was chosen due to the significant change in friction slope between the upper and lower portions of the basin. This change in land grade can be visualized by viewing the contour map

(Figure 28) below.

4/30/2011



dividing up the basin was due to the significant change in the west creek channel friction slope

about halfway down its length (the point at which the two upper and two lower basins in Figure

24 converge). The friction slope in the Upper Reach (Reach 1) is approximately 0.0074 feet per

feet (ft/ft) and the slope of the Lower Reach (Reach 2) is about 0.0036 ft/ft. The friction slopes,

side slopes, lengths and bottom widths of each reach were found by analyzing the LiDAR

elevation data for the west creek. These values were input into the WinTR-55 window shown in

Figure 25 channel not

maintained with a clean bottom and brush on the sides (Mays, 2005). The definition of the entire

west creek basin into smaller areas and reaches then sets up the runoff flow path to be used by

the WinTR-55 program.

The flow path is as follows (names refer to those labels in Figure 24): runoff from the Upper

Basin Drainage will accumulate and flow into the head of the Upper Reach, this Upper Reach

flow will travel downstream to the head of the Lower Reach where runoff flows from the Left

and Right Bank Upper Basins will converge and add to the flows entering the head of the Lower

Reach. The Lower Reach flow is then conveyed to the English River while gaining the runoff

flow of the Left and Right Lower Basins just south of Kalona.

Figure 25: WinTR-55 reach data entry window. The west creek was divided into two reaches due to the change in friction slope from the upper to lower basin areas. The geometry of each reach was determined using LiDAR data

and the manning roughness was assumed as 0.050 (Mays, 2005).

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After defining the flow path and reach geometry of the model, the next step was to define the

attributes of each sub-basin in the main window of the WinTR-55 program (Figure 26). The

figures (Figure 27 through Figure 29) on the following pages were used to determine the land

use, surface area, average slope, and hydraulic length of each sub-area. The hydraulic length and

c Figure 26)

using equations (1), (2), and (3).

Figure 26: Main window the WinTR-55 program. The attributes of each sub-area are defined in this window.

The land area data (Figure 27) was used to calculate the USDA Natural Resources Conservation

Service (NRCS) the surface area and curve number (CN) for each sub-area. Curve numbers are

a function of land use, antecedent soil moisture, and other factors affecting runoff and retention

in a watershed (Mays, 2005). For the west creek drainage area a soil class C (Iowa Department

of Transportation, 2011) and type two antecedent moisture conditions (AMC II) were assumed.

A class C soil is characterized as soil usually high in clay content, and AMC II is an average soil

moisture condition (Mays, 2005). Curve numbers range from 0 to 100, with 100 indicating the

greatest amount of runoff potential. For instance paved areas have a CN of 98 were as forested

land have CN of 65 (Mays, 2005).

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Figure 27: West creek drainage basin land use. The land use for each sub-area was used to develop a USDA Natural Resources Conservation Service (NRCS) weighted curve number (CN) for the WinTR-55 program. A full

Water Resources Engineering by Larry Mays. The weighted curve number was calculated by summing the product of the CN for a particular land use by the percentage of area that land use took

up in each sub-area for all of the land uses in a sub-area.

4/30/2011



The next parameter to be defined was the time of concentration (Tc

for a watershed is the time for a particle of water to travel from the hydrologically most distant

(Mays, 2005)

rameters

had to be defined: the hydraulic length and average slope of each sub-area. The lag method is

defined by equations (1), (2), and (3). Figure 28 was used to trace the flow path of a drop of

water perpendicular to the 10 foot contour lines in each of the sub-basins. Multiple flow paths

were used in order to find the average slope of the sub-area. The hydraulic length of the sub-area

was taken as the straight-line distance between the outlet of the sub-basin and most distance

point. The slope lines and hydraulic length lines are represented in Figure 29.

(1)

(2)

(3)

S = potential maximum retention of runoff by soil

CN = weighted curve number for sub-area

tL = time in hours from the center of mass of the runoff to the peak discharge

L = hydraulic length (ft)

Y = average slope (%)

tC = time of concentration (hrs)

4/30/2011



Figure 28: The land contours of the west creek drainage area. Each line represents a 10 foot change in elevation. The change in the frequency or density of these lines between the upper and lower portions of the drainage area is

indicative of the grade change that determined the breakdown of the drainage basin into five sub-areas and two reaches. Figure 28 was also used to generate the slope lines shown in Figure 29 by tracing the path a drop of rain

water would take to reach the west creek. *Note: flow is perpendicular to the contour lines.

4/30/2011



Figure 29: In addition to determining the curve number for each sub-area, the hydraulic length and average slope were also necessary. These numbers were used to determine the time of concentration for each sub-area. The

hydraulic length (pink) is the distance between the sub-area outlet and the most distant point in the sub-area. The slope is the average land slope of the sub-area; found by tracing flow lines using the contour map (Figure 28).

4/30/2011



The last parameter defined in the WinTR-55 program prior to executing the flow computations

was the storm data (Figure 30). The program itself makes this task easy by having pre-loaded

data for the most appropriate storms for each county in Iowa. Therefore by defining the county

and state in the main window (Figure 26) and opening the storm data window (Figure 30) all that

defined as a type II rainfall distribution. This distribution represents a synthetic storm

hyetograph developed by the USDA NRCS, with the type being specific to a geographic location

in the United States (Mays, 2005). Effectively the data is stating that a 100-year or a storm with

a 1% chance of occurrence during any one year period lasting 24 hours will have a total

accumulation of 6.7 inches of rain.

Figure 30: The storm data for the geographic region is defined by selecting the state and county of interest in the main window (Figure 26). WinTR-55 automatically loads the appropriate rainfall distribution and accumulation

amounts for return periods of interest for Washington County, Iowa.

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With all of the data now entered into the program the computations were executed in order to

develop flow rates in the basin. The output table from the WinTR-55 program is shown in

Figure 31. The table lists the peak flows and time of peak flow for each of the return periods,

sub-areas, and reaches. Figure 32 is a graphical representation of the hydrograph (flow rate vs.

time) for the upstream section of Reach 1. The upstream peak flows for Reach 1 and Reach 2

will then be used in the HEC-RAS program, discussed in the following section, to determine if

the west creek exceeds its banks during these flows.

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Figure 31: The tabulated results of the WinTR-55 program for the unchannelized west creek. These results all show a peak flow in the channel occurring around 12 hours after the start of any of the 24 hour storms (Figure 30) with the 100-year storm yielding a total outlet flow of 3970 cfs with 1284 cfs at the beginning of Reach 1 and 2592 cfs at the

beginning of Reach 2. The latter two flows will be used in the HEC-RAS model to determine if the west creek exceeds its banks.

4/30/2011



Figure 32: Hydrographs of the upstream end of Reach 1 for the 2 through 100 year storms. Although the resolution is poor, the general shape of the hydrograph can be seen. Flow rates peak at about 12 hours for each case as expected using a synthetic storm hyetograph that peaks in rainfall at the 12 hour point. The

hydrograph for Reach 2 is similar in shape, but with higher flows due to the accumulation of runoff from the upper bank basins.

4/30/2011



B.1.2: HEC-RAS West Creek Hydrologic Model

The HEC-RAS is software that performs a variety of one-dimensional hydrologic modeling

analysis functions (U.S. Army Corps of Engineers (USACE), 2010). For the purposes of this

English River at one of two condition; 100-year flood stage (656 feet) and normal stage (643

feet). This was done to determine the out-of-bank conditions for the west creek pre-design

improvements and post-design improvements. To run these simulations pre- and post-design the

only factor that was changed was the m of the channel. In its current state the

roughness will effectively drop by half to 0.025 (Mays, 2005)

means less resistance to flow exists within the channel and therefore; the channel will be able to

convey a higher flow before exceeding its banks.

The HEC-RAS model used by Anvil Engineering was developed under contract of FEMA by

STARR. The model was then provided to Anvil by Mr. Scott Ralston, P.E. of the Iowa DNR.

As with the WinTR-55 software discussed above, data specific to the west creek was required to

be entered prior to the proper function of the HEC-RAS model.

The first set of information required is the geometry of the channel. Figure 33 shows the

geometric data editor window of HEC-RAS. In this window a sketch is made of the hydrologic

entity of interest. In this case, the sketch is actually highly accurate data imported into the HEC-

RAS program from a geographic information system (GIS) program. The west creek channel in

Figure 33 is then represented by the blue line, the green lines intersecting the channel are where

cross-section profiles were taken of the creek and its banks. A typical cross section is shown in

Figure 34. With the geometry correctly entered the only additional information required by the

program is of the flow in the channel.

The flow data used in the model are those flows determined using the WinTR-55 program with

the downstream boundary conditions at the English River set using data from the USGS gage

analysis in Section 1.2.

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Figure 33: Geographic model of the west creek used by the HEC-RAS program. Each of the lines intersecting the creek is known as cross-sections. These cross-sections are used to defined the channel length, slope, bank stations,

and roughness.

Figure 34: Cross section editor window of the HEC-RAS software. This particular cross section was taken at eft and right banks of the

creek. In the particular scenario modeled above the flow in the creek channel exceeds the banks.

4/30/2011



After running the HEC-RAS program the results show the level and extent of flows along the

defined geometry of the channel. Figure 35 below shows a three dimensional rendering of the

west creek pre-improvements with a 100-year storm flow and with a 100-year event in the

English River. The red lines are the banks of the west creek and run through the center of the

blue shaded area which indicates the level and spread of the flows. In this scenario the west

creek is definitely out of its bank. This is very similar to the output that was generated by

STARR for the development of the new FEMA flood maps for Kalona. Though this scenario

was actually run at about 1000 cfs less in the west creek in both Reach 1 and Reach 2 due to the

information gained from the WinTR-55 model.

Figure 35: The above figure is one of many outputs from the HEC-RAS program. This particular case is the 100-year flow in the west creek as defined by the WinTR-55 program with the downstream water elevation (the point at which the creek discharges into the English River) at the 100-year flood level for the English River (656 feet above sea level). The red lines define the banks of the west creek. From this model it is easy to conclude that a 100-year

flow will cause the west creek to exceed its banks and this is compounded by a concurrent 100-year event in the English River.

This section was meant to discuss how the different scenarios were modeled using available data

for the watershed and hydrologic modeling software. Details of each specific design are

discussed further in the following sections of Appendix B, with the other modeled scenarios

discussed in the appropriate sections of Section 2.0.

4/30/2011



B .2: A lternative 1 Design and Cost Calculations

B.2.1: Channel Side Slope and Coverage Area It was determined to line the channel from Station 15234.77 to Station 8204.57 and from Station

4166.94 to Station 3165.98 with riprap due to these lengths being relatively unconstrained by

urban development. Gabion boxes will be used from Station 8204.57 to Station 4166.94. An

approximation of the geometric characteristics of the west creek was required to calculate the

amount of material needed to completely line the channel. This channel geometry: bank height,

channel length, and side slopes, were determined using ArcGIS resources and the HEC-RAS

model discussed in Appendix B.1.2. Table 9 contains variables obtained from the HEC-RAS

River. The total length of the channel is therefore ~19227 feet, with the distance between any

two stations being the difference between their respective station numbers. The left and right

elevations are the bank station elevations in feet above mean sea level at each cross-section

station. The ground elevation is the elevation in feet above mean sea level of the bottom of the

west creek at each station. The elevation of the creek bottom along with the bank station

elevations and horizontal distance between the creek bottom and bank station were used to

calculate the left and right side slopes. The side slopes are reported in Table 9 as the number of

horizontal feet traveled per one foot in the vertical direction. The area of the bank between two

stations was next to be calculated by computing the average bank slope and bank length between

two stations and multiplying it by the distance between the two stations. The results of this

analysis are presented in Table 9. A sample calculation is presented in the next section of this

appendix: B.2.2.

4/30/2011



Table 9: Summary table of data used to calculate the amount of material (stone and gabion boxes) required to line the west creek. Column headers highlighted with light green are data obtained from the HEC-RAS model discussed in Appendix B.1.2. Creek stations are color coded according to whether they will receive a riprap lining (orange) or gabion (purple). A discussion of how the values in columns that are not highlighted can be found in Appendix B.2.2.

731.60 732.07 730.65 0.0 14.3 16.5 1.42 2.42 13.56 23.43 13.77 23.55 0.0 0.0 -‐-‐-‐-‐-‐-‐-‐720.66 719.58 717.91 1001.9 13.8 21.6 2.75 3.75 38.09 36.07 38.28 36.26 26.02 29.91 2897.1 3329.4 -‐-‐-‐-‐-‐-‐-‐712.65 712.22 711.07 873.1 19.8 17.5 1.58 2.58 31.39 20.21 31.49 20.37 34.89 28.32 3384.2 2747.2 -‐-‐-‐-‐-‐-‐-‐703.59 703.66 702.49 1127.9 35.2 18.1 1.16 2.16 38.87 21.03 38.93 21.14 35.21 20.76 4413.2 2601.4 -‐-‐-‐-‐-‐-‐-‐698.7 698.2 696.3 989.0 12.4 10.2 2.38 3.38 29.54 19.98 29.73 20.26 34.33 20.70 3772.9 2274.9 -‐-‐-‐-‐-‐-‐-‐694.8 695.2 693.0 771.4 23.5 17.2 2.17 3.17 40.40 37.22 40.52 37.36 35.13 28.81 3010.9 2469.3 -‐-‐-‐-‐-‐-‐-‐687.9 689.7 683.5 1198.0 6.6 3.2 6.20 7.20 29.38 20.03 30.25 21.28 35.39 29.32 4710.6 3903.0 -‐-‐-‐-‐-‐-‐-‐686.9 685.6 678.2 1019.0 2.3 2.7 8.63 9.63 20.00 19.92 22.19 22.13 26.22 21.71 2968.9 2457.4 -‐-‐-‐-‐-‐-‐-‐683.9 682.9 675.9 1044.8 3.6 4.7 8.02 9.02 29.14 32.89 30.50 34.10 26.35 28.12 3058.6 3263.8 -‐-‐-‐-‐-‐-‐-‐677.3 676.4 672.9 964.4 4.9 9.1 4.45 5.45 21.64 31.62 22.31 32.08 26.41 33.09 2829.6 3545.9 -‐-‐-‐-‐-‐-‐-‐675.0 674.2 665.0 970.3 1.5 3.2 10.08 11.08 14.65 29.52 18.37 31.53 20.34 31.81 2193.0 3429.1 -‐-‐-‐-‐-‐-‐-‐671.2 672.5 662.6 1062.3 2.4 2.8 9.96 10.96 20.85 28.04 23.55 30.10 20.96 30.82 2474.0 3637.4 -‐-‐-‐-‐-‐-‐-‐668.4 668.6 658.5 1022.0 2.1 3.1 10.09 11.09 20.77 31.34 23.55 33.25 23.55 31.67 2674.3 3596.9 1260664.2 663.5 655.8 1009.3 2.5 2.9 8.35 9.35 20.70 22.41 22.72 24.28 23.13 28.76 2594.1 3225.7 1050661.0 660.6 652.4 1086.6 2.4 2.9 8.62 9.62 20.73 23.84 22.85 25.71 22.78 24.99 2750.5 3017.6 1162658.4 657.8 648.7 919.7 2.0 3.1 9.79 10.79 20.01 28.21 22.73 30.20 22.79 27.96 2329.0 2856.9 1104655.5 655.5 646.0 1001.0 2.9 2.1 9.53 10.53 27.95 20.02 29.87 22.62 26.30 26.41 2924.9 2937.5 -‐-‐-‐-‐-‐-‐-‐655 655 643 3166.0 2.9 2.1 12.00 13.00 34.80 25.20 37.15 28.36 33.51 25.49 11787.0 8966.2 -‐-‐-‐-‐-‐-‐-‐0.00

Bank Height [ft]

Left Width [ft]

Lt. Bank Length [ft]

Right Width [ft]

3165.98

19226.7118224.8017351.7216223.79

8204.577182.556173.22

14463.3513265.3112246.3511201.5710237.229266.88

15234.77

Design Height [ft]

5086.664166.94

Ground Elevation

[ft]

Rt. Bank Length [ft]

Avg. Lt. Length [ft]

Dist. Between

[ft]

# of Gabion Boxes

Coverage Area Rt. [yd2]

49814

StationLt.

Elev. [ft]

Rt. Elev. [ft]

Lt. Slope (H:V)

Rt. Slope (H:V)

Coverage Area Lt. [yd2]

Avg. Rt. Length [ft]

Total Sq. Yards:

Total # Boxes

4576

Total yd3

of Boxes9152Total yd3

of riprap33209

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B.2.2: Sample Calculation Station 15234.77

To demonstrate in further detail how the calculations discussed in Section B.2.1 were conducted

a sample calculation for Station 15234.77 will be performed.

First the geometric data characterizing the channel at Station 15234.77 was taken from the HEC-

RAS model discussed in Section B.2.1 (Table 10). This data was used to calculate the side

slopes of the channel by entering the data into Microsoft Excel and applying a linear trend line to

the points representing the right and left banks (Figure 36).

Table 10: HEC-RAS data for the west creek at Station 15234.77. The black highlighted numbers indicate the creek bottom. The first and last pair of numbers are the bank stations.

Figure 36: The data from Table 10 was plotted using Microsoft Excel and linear trend lines were applied to find the

slop of each bank.

Position Elevation9968.85 698.679978.85 697.359988.85 696.449998.86 696.2910008.86 697.0610018.86 698.24

y = -‐0.0804x + 1500.1R² = 0.9044

y = 0.0978x -‐ 282.01R² = 0.9859

695.5

696.0

696.5

697.0

697.5

698.0

698.5

699.0

9960 9970 9980 9990 10000 10010 10020 10030

Elevation [feet]

Horizontal Position [feet]

Station 15234.77

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The slopes of the linear trend lines in Figure 36 are interpreted as the number of feet traveled in

the vertical direction for every foot in the horizontal (V:H). The inverse of these slopes (H:V)

was taken as the side slope for the channel at Station 15234.77 in order to compare them with the

slopes specified by state standards for the placement of riprap.

The bank height of the station was found by subtracting the left or right bank elevation,

whichever was greater, from the ground elevation. To find the design height, one foot was added

to the bank height (Table 11).

Table 11: Definition of Calculated Depths

The widths and bank lengths calculated below are for the left side only, but the procedure is

identical for the right side. Essentially the Pythagorean Theorem was used to determine the bank

length (Figure 37).

Figure 37: Channel Schematic

Bank Height Maximum bank elevation (left or right) minus the elevation of the creek bottom

Design Height Bank Height plus 1 foot

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After calculating the lengths of the left and right banks, the average bank length between stations

was calculated. This average was then multiplied by the distance between station to generate an

area of coverage in square yards.

Assuming a 2 foot thick layer of riprap will be applied yields a total volume of required riprap of

33,209 cubic yards (Table 9).

To calculate the number of gabion boxes required for each length between stations was a more

straight forward calculation. With the distance between stations known, the design height

determined, and the dimensions of a gabion box given (6 feet long, 3 feet wide, 3 feet tall), the

number required was therefore determined by multiplying the length divided by six by the design

height divided by three. This number was then doubled to account for both banks.

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Figure 38: Position of riprap and gabion boxes

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B.2.3: Costs It is important to note that these prices will fluctuate due to the construction bidding process.

Assume a riprap density of 120 pounds per cubic foot at a price of $35 per ton (Van Dyke,

2011)

(Northern Iowa Construction Products,

2011)

The stone needed to fill the boxes is quoted at $10 per cubic yard

Assume l below and on the backside of each box (Iowa SUDAS, 2008)

The backfill aggregate is quoted at $18 per cubic yard (Cherry Hills Inc., 2009)

Assume 1 of excavation for each gabion box and $2.50 per per excavated

Labor costs are estimated by multiplying the material costs by a factor of 1.5.

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B.2.4: Summary Table

Table 12: Summary of Bank Stabilization design and costs for Alternative 1

Tons of riprap 53,800

Length of west creek covered by riprap (ft)

8,032

Number of gabion boxes 4,576

Tons of stone for gabion boxes

15,000

Length of west creek covered by gabion boxes (ft)

4,038


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B .3: A lternative 2 Design and Cost Calculations

B.3.1: Detention Pond Sizing The following sizing of the detention pond for the West Creek in Kalona, IA, is calculated using

the AASHTO (American Association of State Highway and Transportation Officials) method.

ular hydrograph.

Table 13: Variables for the West Creek Detention Pond Sizing

QP 1000 cfs Design peak inflow (1000 cfs)Qa 450 cfs Design allowable outflow (450 cfs)tb 3 hours Base time of triangular hydrographVS 2.97E106 ft3 Required volume of detention basin (calculated)

Depth 10 feet Assumed depth of detention basinAS 297,000 ft2 Surface area of detention basin (calculated)SS 300 feet Assumed length of the short side of the detention basinSL 990 ft Length of the long side of the detention basin (calculated)

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Figure 39: Location and Size of the West Creek Detention Pond

B.3.2: Costs

$2.50/yd3 of excavated dirt obtained from Steger Construction Inc.

Additional costs for the construction of the detention basin beyond simply excavating a whole

would include the spillway and outlet structure construction, and bank protection. To very

roughly estimate these costs an additional 50% of the excavation costs will be added to the total

cost. Labor costs are estimated by multiplying the material costs by a factor of 1.5

Spillway

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B.3.3: Summary Table

Table 14: Summary of Detention Basin design and costs for Alternative 2.

Detention Basin Design Inflow (cfs)

1,000

Detention Basin Design Outflow (cfs)

450

Detention Basin Volume (ft3)

2,970,000

Detention Basin Total Depth (ft)

15

Detention Basin Surface Area (acres)

7


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B .4: Recommended Design A lternative Construction Information

B.4.1 Permitting:

With a project of this magnitude, there are numerous permits and licenses that would need to be

acquired before any construction work could begin. In this report, Anvil Engineering chose to

focus on two main permits or procedures that are viewed as vital to the work laid out by the

preliminary design.

According to Section 404 of the Clean Water Act (1977), any dredged material that will be

disposed of in a wetland or a body of water must first be authorized by the U.S. Army Corps of

Engineers or a state-approved agency. This would include any material removed from the bed of

the west creek. Although it is not certain where the dredged material would be disposed of,

obtaining this authorization would give the contractor more options, which in turn may lower the

bid price for the project.

General Permit No. 2, required by the Iowa Department of Natural Resources (IDNR), is

th industrial activity for construction activities (land

disturbing water sources downstream of the construction. Also, a permit such as this one requires

an initial inspection followed by repeated inspections throughout the duration of the project to

ensure the permit is still valid.

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Appendix C : A nvil Engineer ing Project Costs

C .1: Anvil Engineer ing Annual O perating Expenses Summary

See Appendix D.3 for Anvil Engineering vacation and sick day policy

287,150.00$ 107,600.00$

105,900.00$

21.2%

37.5%

1760 hours30 days10 days

64.00$ per hour56.00$ per hourStaff Engineer

500,650.00$ Esti mated Total Ope rati ng Costs

Fringe Be ne fit Rate

N e t B illable Hours pe r e mploye eVacation / Sick Days*Holidays

Hourly RatesProject Manager

Direct CostsSalariesFringe Benefits

Indirect Costs

Indire ct Cost Pe rce ntage

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C .2: Direct and Indirect Cost Breakdown

DIR E C T C OSTS

Salaries

Civil Engineer I $54,383 (x4) The average salary for entry level civil engineers in the Iowa City area is $49,000 to $59,000 according to statistics compiled by the website MySalary.com.

Civil Engineering

Supervisor I (Project Manager)

$69,618 (x1) The average salary for entry level civil engineering supervisors in the Iowa City area is $64,500 to $74,000 according to statistics compiled by the website MySalary.com.

Salary Total $287,150

F ringe Benefits

Social Security $17,900 6.2% of payroll The Federal Insurance Contribution Act tax states this is the standard deduction for employers.

Medicare $4,200 1.45% of payroll The Federal Insurance Contribution Act tax states this is the standard deduction for employers.

Health Insurance $26,000 9.0% of payroll Based on the Bureau of Labor Statistics the average employer cost in the Midwest is between 8.0 to 10.7%. The chosen value will provide health coverage without a high deductible.

Compensation Insurance

$11,700 4.05% of payroll Information from WorkersCompensation.com was used to generate this value as the necessary amount to completely cover our employees in the event of an on-the-job accident.

Unemployment Insurance

$19,000 6.6% of payroll Based on the Bureau of Labor Statistics information, this value was chosen to ensure that our employees can maintain their standard of living for the recommended period in the event of a staff downsizing.

401k $28,800 10.0% of payroll

Anvil Engineering promotes an outlook towards the future and ensures our employees future by contributing 10% to their retirement accounts.

Benefits Total $107,600

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INDIR E C T C OSTS

Lease $13.200 Expected monthly rent of $1,100

Office Materials $7,500

Paper, IT Support $3,500

Software and computer assistance Office

Maintenance $5,000 covered in rent)

Software $10,000 5 leases of AutoCAD

Travel $17,000 Business trips to clients and conferences

Vehicles $19,200 1 sedan & 5 pick-ups with a total monthly payment of $1,600

Vehicle Maintenance

$4,000 Oil changes, tires, brakes, and unforeseen problems

Vehicle Insurance $6,000 Comprehensive coverage for each vehicle

Cell Phones $3,500 Cell phones for each engineer & office worker (Note: landline included in the rent)

Advertisement $7,500 Radio, television, magazines/newspapers

Utilities $1,500 Cable and any other service not covered by the rent payment

Equipment $3,000

Safety $1,000 Safety equipment for the employees

Professional Development

$4,000 Periodic training and classroom instruction to maintain a high level of professional knowledge

Indirect Total $105,900

C .3: Annual O perating Expenses Calculations

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Indirect Cost Percentage (IC%):

o

o Fringe Benefit Rate (FBR):

o

o Net Billable Hours (NBR)

o

o

Hourly Rates

o

Sick Days - All employees are allotted 10 sick days per year. Should an employee require more than three

note will be required stating that employee s inability to work. Also,

should an employee require more than 10 sick days per year, that employee will

stating that employee s inability to work.

Vacation Days - All employees will earn two weeks paid vacation per year. In order to earn the two weeks

paid vacation the employee must work at least 40 hours per week. Furthermore, employees that have

worked with Anvil Engineering for more than 5 years will earn three weeks paid vacation per year and

employees that have worked with Anvil Engineering for more than 10 years will earn four weeks paid

vacation per year.

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Appendix D: Additional figure information

Figure 1

- Image obtained from the Geology.com website under the submenus for U.S. Maps Iowa Maps

Figure 2

- Image was provided by Kalona City Administrator Ryan Schlaumbaug at a city meeting on March 3rd, 2011

Figure 3

- Image was obtained from the Iowa Flood Center website (http://www.iowafloodcenter.org/

Figure 4

- Image was developed using ArcGIS software and GIS information obtained from the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Geospatial Data Gateway (http://datagateway.nrcs.usda.gov/GDGOrder.aspx). Land use information for the English River Watershed was obtained by downloading the raster map of the National Land Cover Dataset for Iowa and clipping this raster with the English River Watershed shapefile downloaded from University of Iowa GIS Library (ftp://ftp.igsb.uiowa.edu/gis_library/Watersheds/Stream_Watersheds/Mississippi_River/Iowa_River/English_River/). Each block in the image represents a 30 meter by 30 meter area.

Figure 5

- Image was taken obtained the Iowa Flood Center website (http://www.iowafloodcenter.org/

Figure 6

- Graph was developed using Microsoft Excel and data from the USGS stream gage located south of Kalona, Iowa, monitoring the English River.

Figure 20

- Image was developed using ArcGIS software, aerial photos of Kalona, and FEMA flood plain layers provided by Mr. Duane Royer, GIS Coordinator for Washington County,

4/30/2011



Iowa. Aerial photos were obtained from the Iowa State University Iowa Geographic Map Server (http://ortho.gis.iastate.edu/search.html) at a 1 meter by 1 meter pixel resolution.

Figure 21

- Image was developed using ArcGIS software, aerial photos of Kalona, and GIS layers provided by Mr. Duane Royer, GIS Coordinator for Washington County, Iowa. GIS layers provided by Mr. Royer include a parcel map (with associated attribute table containing FY10 assessed property values) and the FEMA flood plain layer. Aerial photos were obtained from the Iowa State University Iowa Geographic Map Server (http://ortho.gis.iastate.edu/search.html) at a 1 meter by 1 meter pixel resolution. These data were then used in conjunction to determine whether a parcel was in, not in, or partially in the 100-year flood plain. If the parcel was partially in the flood plain the aerial images were utilized to determine whether any structure on the parcel was in, not in, or partially in the 100-year flood plain.

english river watershed plancityofkalona.org/vertical/sites/{711028d0-fd55-400a-8310-1e072956… ·...

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