leon creek watershed master plan leon springs business association september 15, 2011
TRANSCRIPT
Leon Creek Watershed Master Plan
Leon Springs Business Association
September 15, 2011
Agenda
• Historic Floods• BRWM Partnership• BRWM Website• Leon Creek Watershed Master Plan• Leon Creek USACE Feasibility Study
Flood of 1921
SAR - Pecan St. Bridge
1998 Floodvement Projects
Leon Creek - IH10 near Camp Bullis & La Cantera Rd.
Olmos Creek - Hwy 281/Basse Rd & Olmos Basin Golf Course
2002 Flood
Need for Partnership
• Flooding knows no boundaries• Sharing of resources• Project vetting process
Bexar Regional Watershed Management
• Interlocal Agreement (ILA) established a partnership for watershed management between:• Bexar County (County)• City of San Antonio (COSA) • San Antonio River Authority (SARA)• 20 Suburban Cities
BRWM Objectives
• Flood Control• Storm Water Management• Water Quality
• DFIRM website– DFIRM floodplains– Aerial imagery–NFIP information
• Website will be regularly updated
BRWM websitewww.bexarfloodfacts.org
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Leon Springs DFIRM
Leon Creek Watershed Master Plan
This project will deliver a Holistic Watershed Master Plan for the Leon Creek watershed
• Flood control projects• Water quality – qualitative analysis• Alternative development techniques
• Phase 1 - Regional Detention Projects• Phase 2 - Natural Water Way Conveyance Projects• Phase 3 - Combinations of Phase 1 and Phase 2
projects
Leon Creek Watershed Master Plan
• Leon Creek Watershed–Western Bexar
County– Area: 237 sqmi– Approximately
1,500 buildings in the 100-year floodplain
Damage Density Map
Watershed Annual Flood Damages
• Leon Creek: $3,064,000• San Antonio River: $7,703,000• Salado Creek: $4,721,500
Note: Damage calculation includes 10-yr, 50-yr, 100-yr, 100-yr FC, and 500-yr storm events
• Phase 1 (April 2008 – December 2008)– RSWFs– Stream/roadway crossing analysis
Leon Creek Watershed Master Plan
• 14 projects
• Total Cost: $275.6 million
• Phase 2 (April 2009 – April 2010) – NWWC Projects– Transportation
Corridor & Utility Crossings
– Stream Scour Analysis
– Alternative Development Techniques White Paper
Leon Creek Watershed Master Plan
• 21 projects• Total Cost: $147.8 million
• Phase 3 (May 2010 – January 2011)– RSWF & NWWC Project combinations– LIDs, BMPs, NCD,
Riparian/conservation buffers– Qualitative Water Quality assessment
Leon Creek Watershed Master Plan
• Phase 3– Non-structural
options evaluation:• Quantified flood
mitigation of BMPs• Recommendation:
future development with BMPs to reduce hydrologic impact and drainage infrastructure expense
Leon Creek Watershed Master Plan
http://imnh.isu.edu
• Phase 3 BMP & LID Modeling Results
Leon Creek Watershed Master Plan
• Rain barrels, rain gardens• Green roofs, pervious pvmt.• Conservation development1
• Cisterns, green roofs• Conservation development2
• Bioretention and pavement
1. Non-infiltration BMPs over karst regions (e.g. rainwater harvesting, green roofs)2. Infiltration BMPs (e.g. bioretention, rain gardens, pervious pavement)
Bioretention/Rain Gardens
http://www.beautifulleafgardens.com/garden_design
Office Building Rain Garden in Minnesota
Rain Water Harvesting
http://www.gulfcoastrenewableresources.com/rainwater_harvesting
WaterHarvest Slimline Tank
Permeable Pavements
http://www.casfm.org/stormwater_committee/MBP-02.htm
Modular Block Pavement - 1335 Elati St Denver, COPhoto Courtesty of Wenk Associates
Conservation Development
http://www.upstateforever.org/programs_comDes.html
Cluster Development minimizes impervious cover and promotes open or green space.
Traditional Development Cluster Development
LCWMP – Phase 3 Cost Estimates
Total cost : $140 million
LCWMP – Phase 3 Cost Estimates
Impacts of Implementing All Recommended Projects
• Flood Damage Reduction– $1,165,300
• Total Construction Cost– $140,000,000
• Flood Reduction Ratio– 0.26
Next Steps for SARA
• Detailed Water Quality Modeling– Identification of Low Impact Development
projects– Identification of BMPs
• Stream Preservation, Rehabilitation, and Restoration projects
• DFIRM map maintenance – FEMA LOMR Delegation for SARA
• Inclusion of Sustainability Practices using TBL approach
Contacts – Watershed Management
Russell Persyn, PE, PhD, CFMManager(210) [email protected]
Rafael Arias Jr., PE, CFMEngineer(210) [email protected]
Yolanda McGinnisAdmin. Assistant(210) [email protected]
Questions?
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