Iowa Watersheds Project

Project Update:Middle Raccoon River Watershed

Larry WeberDirector, IIHR – Hydroscience and Engineering

February 11, 2013

Project UpdateIowa Watersheds Project overview – Phases I & IIProject timelineModeling approach in Middle Raccoon River Watershed

HEC-HMS HydroGeoSphere

Watershed Monitoring USGS & Iowa Flood Center

Watershed trends Monthly & annual data

Soap Creek ExampleDiscussion

Iowa Watersheds ProjectOverview:

To plan, implement, and evaluate watershed projects to lessen the severity and frequency of flooding in Iowa

Specific Project Goals:Maximize soil water holding capacity from

heavy precipitationMinimize severe scour erosion and sand

deposition during floodsManage water runoff in uplands under

saturated soil moisture conditionsReduce and mitigate structural and

nonstructural flood damages

Phase I: Overview

Hydrologic model developmentData analysis and community engagement Identify areas in subwatersheds for project

construction

Hydrologic Assessment

Phase II: Overview

Engage landowners to construct projects in subwatersheds

Projects may include: Active and passive distributed

storage, Floodplain restoration or easements Buffer strip installation and

enhancement Advanced tile drainage

Monitor impact of constructed projects and evaluate feasibility at a larger scale

Project Construction & Implementation

Engagement of Watershed Management Authority and private land owners will be vital to project success

Project TimelinePhase IJune 2012 Watershed kickoff meetings

Commence data collection and watershed modeling

Fall 2012 Meeting to discuss model development & data needs

Winter 2013

Meeting to discuss initial findings of hydrologic modeling & community/landowner engagement in the watershed

Spring 2013

Continue quarterly meetings to discuss modeling progress, potential projects for implementation, share progress on other watershed activities

Fall 2013 Complete and present hydrologic assessment

Winter 2014

Finalize hydrologic assessment report

Project TimelinePhase IIFebruary 19, 2013 Identify HUC 8s for Phase II

Spring 2013 Identify HUC 12s for project construction, WMA begins dialogue with IEDA regarding Phase II Funds

Summer & Fall 2013 Explore project locations, commence project design

Winter & Spring 2014 Design projects

Summer 2014 – Summer 2015

Construct projects

Summer 2014 – 2017 Monitor & assess projects

Summer 2017 Finalize Phase II report

Phase I: Hydrologic Assessment

Develop and run basin-scale hydrologic models to estimate watershed responses to rainfall events HEC-HMS HydroGeoSphere

Modeling Approach

Analyze results to understand and quantify watershed response

Identify areas within the watershed where projects may reduce flood damages downstream

Start with a 3 m resolution Digital Elevation Model (DEM)

Generate required terrain layers

Identify stream centerlines

Model Development – HEC-GeoHMS

Model Development – HEC-GeoHMS

Outlet

Bayard

Divide watershed into 349 subbasins each with at least one stream reach

Panora

Model Development – HEC-GeoHMS

Higher curve numbers indicate higher runoff rates

Generate weighted curve number for each subbasin to understand amount of rainfall converted to runoff

Populate river data River Length River Slope Basin Slope Longest Flowpath Basin Centroid Centroidal Longest Flowpath

Populate subbasin data SURGGO Soil Data NLCD Land Cover

Establish grid network for application of radar rainfall

Model Development – HEC-GeoHMS

Use rain & stream gauge data and USGS & NWS reports for record rainfall events to ensure model reflects observed watershed response

Model Calibration – Rain Events

June 7 - 13, 200810.6” reported in Carroll for entire event,

over 1.6” recorded at Coon Rapids in12 hrs Stage at Panora – 10.35 ft Stage at Bayard – 9.81 ft

June 26 - 28, 2010 6.9” recorded over 2-day period at Carroll, 2.3”

recorded at Coon Rapids in 1 hr Stage at Panora – 9.91 ft Stage at Bayard – 10.39 ft

Historical Rain Events

Stream Monitoring in IowaIowa Flood Center Sensors

Affordable, effective way to monitor streams 130 sensors deployed across Iowa Sensors report stage automatically and frequently Data is accessible and available in real-time through

Iowa Flood Information System (IFIS) Coupled with USGS gages statewide, sensors

enhance monitoring across Iowa

Middle Raccoon Monitoring

Trends at USGS Gages - Annual

Average Annual Discharge

1913 1921 1929 1937 1945 1953 1961 1969 1977 1985 1993 2001 2009

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Raccoon River at Van Meter, IA(1915-2011)

Year

Dis

charg

e (

CFS)

Trends at USGS Gages - Annual

Annual Peak Discharge

1913 1923 1933 1943 1953 1963 1973 1983 1993 2003 2013

0

10000

20000

30000

40000

50000

60000

70000

80000

Raccoon River at Van Meter, IA(1915-2011)

Year

Dis

charg

e (

CFS)

Trends at USGS Gages - Monthly

Average Monthly Discharge

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

500

1000

1500

2000

2500

3000

3500

4000

Raccoon River at Van Meter, IA(1915-2011)

Month

Dis

charg

e (

CFS)

Phase I: Hydrologic AssessmentHydrologic models have been developed for Soap

and Chequest Creek to estimate and understand watershed response to rainfall events

Evaluation of existing structures in Soap Creek to quantify water quantity impact and applicability to other watersheds

Identify areas where additional projects may reduce flood damages downstream

Soap Creek302 sub-basins

Chequest Creek 267 sub-basins

Break down structures into groups based on construction year:

1992-1993 12 Structures1994-1999 33 Structures2000-2005 43 Structures2005-2008 22 Structures2009-2012 22 Structures

Total: 132 Structures

Pond Construction

Pond Construction:Prior to 1993

1993 Total Area (km2) Total Area (mi2) Total Area (acres)647.497 250 160000

% Controlled Area Controlled (km2) Area Controlled (mi2) Acrea Controlled (acres)1.81% 11.69 4.51 2889.01

Pond Construction:Prior to 2005

2005 Total Area (km2) Total Area (mi2) Total Area (acres)647.497 250 160000

% Controlled Area Controlled (km2) Area Controlled (mi2) Acrea Controlled (acres)15.29% 98.99 38.22 24460.09

Pond Construction:Prior to 2008

2008 Total Area (km2) Total Area (mi2) Total Area (acres)647.497 250 160000

% Controlled Area Controlled (km2) Area Controlled (mi2) Acrea Controlled (acres)18.83% 121.93 47.08 30129.55

Pond Construction:Prior to 2012

2012 Total Area (km2) Total Area (mi2) Total Area (acres)647.497 250 160000

% Controlled Area Controlled (km2) Area Controlled (mi2) Acrea Controlled (acres)23.81% 154.18 59.53 38097.58

Pond Construction

Design StormsModeled 24-hour storms at the following return periods

2 yr: 3 inches5 yr: 3.5 inches10 yr: 4.75 inches25 yr: 5.5 inches50 yr: 6.5 inches100 yr: 7.5 inches

Results 100 yr storm, 7.5” of rain

Reduction57.67%

Reduction35.74%

Reduction18.31%

Reduction26.30%

Reduction21.09%

Reduction29.69%

100 yr storm, 7.5” of rain

Pond Storage 100 yr storm, 7.5” of rain

Pond Storage 100 yr storm, 7.5” of rain

Peak Pond Storage 100 yr storm, 7.5” of rain

Prioritizing HUC 12s

Watershed with intrinsic public value/awareness

Headwater regions of the watershedHigh runoff & localized flooding observed

during rainstorms Damages to property – residential, commercial, &

repetitive crop damages Washed out / impassable roadways

Team of diverse stakeholders, technical expertise and local leadership Local, state and federal organizations

Watershed projects, past and proposedLandowner and producer willingness to

participate

Positive Characteristics