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Leon Creek Watershed Master Plan Leon Springs Business Association September 15, 2011

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

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  1. Leon Creek Watershed Master Plan Leon Springs Business Association September 15, 2011

  2. Agenda • Historic Floods • BRWM Partnership • BRWM Website • Leon Creek Watershed Master Plan • Leon Creek USACE Feasibility Study

  3. Flood of 1921 SAR - Pecan St. Bridge

  4. 1998 Floodvement Projects Leon Creek - IH10 near Camp Bullis & La Cantera Rd.

  5. 2002 Flood Olmos Creek - Hwy 281/Basse Rd & Olmos Basin Golf Course

  6. Need for Partnership • Flooding knows no boundaries • Sharing of resources • Project vetting process

  7. 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

  8. BRWM Objectives • Flood Control • Storm Water Management • Water Quality

  9. BRWM websitewww.bexarfloodfacts.org • DFIRM website • DFIRM floodplains • Aerial imagery • NFIP information • Website will be regularly updated

  10. Leon Springs DFIRM

  11. 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

  12. Leon Creek Watershed Master Plan • Leon Creek Watershed • Western Bexar County • Area: 237 sqmi • Approximately 1,500 buildings in the 100-year floodplain

  13. Damage Density Map

  14. 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

  15. Leon Creek Watershed Master Plan • Phase 1 (April 2008 – December 2008) • RSWFs • Stream/roadway crossing analysis • 14 projects • Total Cost: $275.6 million

  16. 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

  17. 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

  18. 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

  19. 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)

  20. Bioretention/Rain Gardens • Office Building Rain Garden in Minnesota • http://www.beautifulleafgardens.com/garden_design

  21. Rain Water Harvesting • WaterHarvestSlimline Tank • http://www.gulfcoastrenewableresources.com/rainwater_harvesting

  22. Permeable Pavements • Modular Block Pavement - 1335 Elati St Denver, CO • Photo Courtesty of Wenk Associates • http://www.casfm.org/stormwater_committee/MBP-02.htm

  23. Conservation Development • Traditional Development • Cluster Development • Cluster Development minimizes impervious cover and promotes open or green space. • http://www.upstateforever.org/programs_comDes.html

  24. LCWMP – Phase 3 Cost Estimates • Total cost : • $140 million

  25. LCWMP – Phase 3 Cost Estimates

  26. Impacts of Implementing All Recommended Projects • Flood Damage Reduction • $1,165,300 • Total Construction Cost • $140,000,000 • Flood Reduction Ratio • 0.26

  27. 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

  28. 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

  29. Questions?

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