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Iowa Watersheds Project
Project Update:Middle Raccoon River Watershed
Larry WeberDirector, IIHR – Hydroscience and Engineering
February 11, 2013
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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
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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
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Phase I: Overview
Hydrologic model developmentData analysis and community engagement Identify areas in subwatersheds for project
construction
Hydrologic Assessment
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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
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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
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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
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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
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Start with a 3 m resolution Digital Elevation Model (DEM)
Generate required terrain layers
Identify stream centerlines
Model Development – HEC-GeoHMS
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Model Development – HEC-GeoHMS
Outlet
Bayard
Divide watershed into 349 subbasins each with at least one stream reach
Panora
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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
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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
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Use rain & stream gauge data and USGS & NWS reports for record rainfall events to ensure model reflects observed watershed response
Model Calibration – Rain Events
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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
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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
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Middle Raccoon Monitoring
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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)
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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)
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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)
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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
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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
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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
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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
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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
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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
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Pond Construction
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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
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Results 100 yr storm, 7.5” of rain
Reduction57.67%
Reduction35.74%
Reduction18.31%
Reduction26.30%
Reduction21.09%
Reduction29.69%
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100 yr storm, 7.5” of rain
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Pond Storage 100 yr storm, 7.5” of rain
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Pond Storage 100 yr storm, 7.5” of rain
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Peak Pond Storage 100 yr storm, 7.5” of rain
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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
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