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Catastrophic Floods in Texas Raymond Slade, Jr., Professional Hydrologist. June 1935. Texas topography and principal sources of moisture. Record Rainfall Rates for Various Durations – The World and Texas. Major Storms along the Balcones Escarpment. Major storms along the Balcones Escarpment.
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Catastrophic Floods in TexasRaymond Slade, Jr., Professional Hydrologist June 1935
Record Rainfall Rates for Various Durations – The World and Texas
Major Storms along the Balcones Escarpment Major storms along the Balcones Escarpment
Ratio of maximum known peak discharges to 100-year peak 1.3 3.3 1.8 2.9 4 1.6 1.5 2.3 2.1 3.5
Flood Stages - Maximum Peak Stages (feet) 24-51 14-42 22-42 17-38 23-60 12-37 13-33 21-42 12-23 30-53 9-39 13-47 7-38 13-40 20-42 17-35 31-50 12-20 20-56 18-42 35-64
Tropical Storm Allison, June 2001 23 deaths $5 billion damages
Big floods in 1998 and 2002 deemed unprecedented and blamed on urbanization by some flood victims Flood history often ignored
Real-time flood data http://waterdata.usgs.gov/tx/nwis/rt
http://floodsafety.com/media/ffa/movieplayer.htm/trailer.htm
Flood Plain ProblemsWhy do people and property flood Texas leads Nation in annual deaths and damages 100-year flood plain – mapped on most streams • Some floods exceed 100-year peak • Some flood plains incorrect - lack of data • Flood plain encroachment increases after last big flood • Some development allowed in flood plains • Urbanization & land cover change increases flood plain • Dams provide false security • Fallible early warning flood prediction models • Low flood plains adopted by some communities
Example of low flood plain Contr New Braunfels adopted 28,000 ft3/s as 100-year flood peak in 1984 Year and associated flood peak in ft3/s