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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 Flood vement Projects.
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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.
2002 Flood Olmos Creek - Hwy 281/Basse Rd & Olmos Basin Golf Course
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
BRWM websitewww.bexarfloodfacts.org • DFIRM website • DFIRM floodplains • Aerial imagery • NFIP information • Website will be regularly updated
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
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
Leon Creek Watershed Master Plan • Phase 1 (April 2008 – December 2008) • RSWFs • Stream/roadway crossing analysis • 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 3BMP & 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 • Office Building Rain Garden in Minnesota • http://www.beautifulleafgardens.com/garden_design
Rain Water Harvesting • WaterHarvestSlimline Tank • http://www.gulfcoastrenewableresources.com/rainwater_harvesting
Permeable Pavements • Modular Block Pavement - 1335 Elati St Denver, CO • Photo Courtesty of Wenk Associates • http://www.casfm.org/stormwater_committee/MBP-02.htm
Conservation Development • Traditional Development • Cluster Development • Cluster Development minimizes impervious cover and promotes open or green space. • http://www.upstateforever.org/programs_comDes.html
LCWMP – Phase 3 Cost Estimates • Total cost : • $140 million
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, CFM Manager (210) 302-3615 rpersyn@sara-tx.org Rafael Arias Jr., PE, CFM Engineer (210) 302-3650 rarias@sara-tx.org Yolanda McGinnis Admin. Assistant (210) 302-3630 yolandam@sara-tx.org