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<br />San Marcos Floodplain Management Plan: A Sustainable Future for Floodplain Management <br />Application for Flood Protection Study Grant <br /> <br />the flood hazard risk. The end products will also be provided in a format to enhance the <br />City's Geographic Information System. <br /> <br />17. A description of the historical flooding and flood damage in the proposed planning <br />area. <br />The meteorlogical characteristics of central Texas, along with an orographic influence <br />caused by the Balcones escarpment, produce conditions which cause large rainstorms in <br />the area. Many of the highest intensities in the world have occurred in Central Texas - a <br />1921 storm in Thrall, Texas, for example, produced 32 inches of raiD in 12 hours, and a <br />1935 storm near D'Hanis, Texas produced 22 inches of raiD in2 hours 45 minutes (Slade <br />1986). Figure 1 illustrates the location of San Marcos relative to the Balcones <br />escarpment, and locations, dates, and depths for selected large rain storms in central <br />Texas. <br /> <br />/' <br /> <br /> <br />EXPLANATION <br />==10 = RAINSTORM DEPTH cotnOUfl-1/I illcr.... Interva' nrletlle <br />""IY 1952 MONTH AND YEAR OF RAINSTORIoI <br />121 NUMBER,OF DAVS OF RAINSTORM <br />FAULT <br />NOTE: unClerscored clly nama. rallr...n, loCatiOn. <br />01 ..In gaga. US.d In ,jg\lrl 3 and 'abla 1 <br /> <br />~ <br />'l\ <br /> <br />~ <br />, <br /> <br />I <br /> <br /> <br />.....U!TfVILI,.! <br />. <br /> <br />o 10 :0 JO .0 IiILIS <br />I . . . . <br /> <br />Figure 1.--Lotations, dates, and depths for selected larse rainstorms in central Texas. <br /> <br />La:O:J ion nt12p <br /> <br />As history demonstrates, this region is highly susceptible to flash flooding conditions generated <br />by these storms, and clearly demonstrates the threat to the communities in the area. The <br /> <br />M:\QCtiveI04P012 SQ/I Marcos UD.PlGranl App/ic-8Ma.dO~xh~it A, Page 12 <br /> <br />December 16, 2004 <br />