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 Flood vement Projects Leon Creek - IH10 near Camp Bullis & La Cantera Rd.

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

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. DFIRM website – DFIRM floodplains – Aerial imagery – NFIP information Website will be regularly updated BRWM website www.bexarfloodfacts.org

10. Leon Springs DFIRM 10

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. Phase 1 (April 2008 – December 2008) – RSWFs – Stream/roadway crossing analysis Leon Creek Watershed Master Plan 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 3 BMP & LID Modeling Results Leon Creek Watershed Master Plan Rain barrels, rain gardens Green roofs, pervious pvmt. Conservation development 1 Cisterns, green roofs Conservation development 2 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 http://www.beautifulleafgardens.com/garden_design Office Building Rain Garden in Minnesota

21. Rain Water Harvesting http://www.gulfcoastrenewableresources.com/rainwater_harvesting WaterHarvest Slimline Tank

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

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

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

29. 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

30. Questions?

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