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San Marcos Floodplain Management Plan: A Sustainable Future for Floodplain Management Application for Flood Protection Study Grant 100-year floodplain (See Attachment 5: Map of Affected Structures, showing 1,185 structures) and querying the 2004 Hays County Appraisal District values. 24. Number of National Flood Insurance Program (NFIP) policies in effect in the proposed planning area. The following table summarizes the NFIP policies in effect in the City of San Marcos and Hays County: NFIP Statistic (as efDeeember 2003) Policies in effect Insurance in.force Written Premium in-force Total N\lDlber of Losses (1978-2003) Total Payments (1978-2003) City of San Marcos 406 $45,015,800 $154,286 335 $3,362,532 Hays County 384 $67,230,700 $166,675 214 $3,193,771 Total 790 S 112,246,500 5320,961 549 56,556,302 Note: Claim information for November 2004 flooding was not available at the time of this grant application. (Source: http://www.fema.gov/nfip/pcstat.shtm) 25. Method for determination of potential cost effectiveness of proposed flood protection solutions. The potential cost effectiveness of proposed flood protection solutions can be determined through a comparison of average annual cost of implementing the solutions to the annualized benefits realized in the reduction of flood damages. Differing levels of damages are associated with varying levels of flooding. Damages are likely to include residences, businesses, accessory structures, streets, bridges, and other public infrastructure. The varying levels of flooding (water surface elevations) correspond to various flood frequencies, ranging from the 2- year to the 100- year events. These flood frequencies provide an estimate of the frequency of recurrence of damages. The City intends to utilize state-of-the-art GIS software (AreGlS 9.0, ArcView 3.2 and HEC-GeoRAS 5.1.1) to assist in damage estimation. The City has already developed numerous GIS datasets for parcels, structures, and infrastructure, and has recently acquired aerial orthophotography and topographic data. Overlaying existing and proposed floodplains to these base layers will not only provide an efficient means of tabulating potential damages, but also enable great flexibility in modeling ''what-if' scenarios to refine the proposed solutions or offer other possible combinations of solutions. The ease of creating "smart" models of inundation depth (ArcGIS) and velocity profiles (HEC-GeoRAS) will also assist in damage estimation and refinement of proposed solutions. The ancillary benefits of various improvements, such as minimizing disruption to critical infrastructure and reducing stream bank erosion and subsidence are more difficult to quantify, and will not be included in the numeric cost-benefit analysis. However, the M:\activeI04P012 SOli Marcos MD.P\Grant App/ic-SMa.&hilfd A, Page 15 December J 6, 2004