City of Sunset Valley

1. City of Sunset Valley Drainage Master Plan Assessment Final Recommendation Report March 24, 2009

2. Project Goal • Assessment of master drainage plan • Development of alternative solutions • Develop final recommendations/report Prioritize Drainage Improvements

3. Review Master Drainage Plan • Plan was comprehensive • Identified riverine overtopping of roadways and structural inundation in Old Sunset Valley • Identified 52 localized drainage issues • Identified a mitigation goal of 5-year level of service • Cost estimates did not include land acquisition or permitting

4. Review New Drainage Concepts • Recharge features • Rooftop harvesting/other • Detention pond footprint • Upstream detention

5. Drainage Mitigation Alternatives

6. Regional Drainage Plan • Partnering with City of Austin and Travis County • Possible Improvements Include • Modifying West Gate Blvd • Regional Channelization • Regional detention • Regional natural waterway maintenance program

7. Regional Drainage Plan • Advantages • Regional approach will achieve higher level of service • Regional solutions typically generate higher benefit cost ratio • Disadvantages • City/County participation unknown • Cost (unknown)

8. Emergency Access Route

9. Emergency Access Route • Advantages • Provides 100 year ingress/egress • Improves public health and safety • Multi use • Disadvantages • Will need to be maintained • Requires 11 easements • Cost $ 720,000

10. Peak Flow Diversion

11. Peak Flow Diversion • Advantages • Multi-use improvement • Provides 5 year ingress/egress • Removes 4 homes & 5 structures form 5 year floodplain • Reduces peak flow rates on other storm events • Disadvantages • Requires clearing of existing natural area • Not accepted by the public • Easement required (1) • Cost $1,600,000

12. Low Water Crossing Improvements • Low water crossing improvements at • Loan Oak Trail • Pillow Road • Reese Drive (not included) • Sunset Trail (not included) • Channel Improvements not included • Improvements may be incorporated together or individually as funding becomes available

13. Low Water Crossing Improvements • Advantages • Provides 5 year ingress/egress • Improves public health and safety • Disadvantages • Does not improve flooding impacts to homes or other structures • Drainage easements may be required on Pillow Road • Cost $1,110,000

14. Buyout Option • Purchase homes within the floodplain • Median home price $300,000 • Cost for demolition and restoration $20,000/lot

15. Buyout Option • 5 Year • Number of homes, 5 • Cost $1,280,000 • 100 Year • Number of homes, 30 • Cost $9,600,000

16. Buyout Option • Advantages • Removes structures from the floodplain • Provides additional greenbelt areas • Provides land for site/regional detention • Disadvantages • Directly impacts several residents • Does not improve ingress/egress

17. Drainage Programs • Reverse 911 • Natural Waterway Maintenance Program • Funding Options • Comprehensive Flood Abatement Program

18. Final Recommendations • Evaluation criteria • Public acceptance 30% • Level of service 35% • Land Acquisition 20% • Cost 15% Total 100%

19. Evaluation Matrix

20. Final Recommendations • No. 1, Regional Drainage Plan -(if not feasible then proceed to No. 2) -Cost: Unknown • No. 2, Emergency Access Route 100-yr LOS Culvert Improvements 5-year LOS -Cost: $1,830,000 • No. 3 Emergency Access Route 100-year LOS Flow Diversion 5-year LOS -Cost: $2,370,000

21. Final Recommendations Programs • Development a natural waterway maintenance program • If necessary for funding investigate the feasibility of creating a storm water utility • Continue the City’s comprehensive flood abatement program • Continue to adopt and enforce ordinances that meet or exceed FEMA requirements to reduce the risk of flooding. • Educate residents in high and moderate risk flood areas about flood insurance