Iowa Watersheds Project

Project Update:Soap Creek & Chequest Creek

Larry WeberDirector, IIHR – Hydroscience and Engineering

February 7, 2013

Quarterly Update

Iowa Watersheds Project Overview/Review – Phases I & II

Project Timeline

Early Results from Phase I Modeling

Prioritizing HUC 12s for Watershed Projects

Iowa Watershed ProjectsOverview

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

Identified four partner watersheds in May 2012

Overview

Hydrologic model development Identify areas in subwatersheds for project

construction

Phase I: Hydrologic Assessment

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

Phase II: Project Construction & Implementation

Engagement of watershed boards 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 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

Gauge data collected from four sites:Hourly Data - OttumwaDaily Data - Albia, Bloomfield, and

Centerville

Historical Rain Events

June 2-9, 1993 7.36” in Bloomfield 2”-4” in Albia, Centerville, and Ottumwa

July 7-17, 1993 2”-5” across area

June 3-13, 2008 4.5”-7” across area

June 9-20, 2011 10.63” measured in Ottumwa 4”-8” measured in Albia, Centerville, and Bloomfield

2” fell in watersheds on 9-10 June, 2011 2-6” additional fell during 13-15 June, 2011

Historical Rain Events

Gridded rainfall from historical rain events

Historical Rain Event: June 13-14, 2011

Historical Rain Event: June 13-14, 2011

Rainfall Distribution: June 13-14, 2011

June 13-19, 2011

Reduction58.33%

Reduction29.00%

Reduction18.52%

Reduction27.98%

Reduction3.81%

Reduction8.09%

Results June 13-19, 2011

Results June 13-19, 2011

Pond Storage, 2011

Pond Storage, 2011

Peak Pond Storage, 2011

Soap & Chequest WatershedsSix IFC stream-stage sensors added in November 2012

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