flood plain information south creek, north creek, catfish - Sarasota ...

Velocities of flow - Water velocities during floodsdepend largely on the size and shape of the cross sections,conditions of the stream and the bed slope, al I of which varyon different streams and at different locations on the samestream. During an Intermediate Regional Flood, velocities ofmain channel flow in the upper reaches of the streams in thestudy area would be 3 to 4 feet per second. In the lowerreaches, the velocities would be somewhat higher averaging 2to 12 feet per second. It is expected that velocity of flowduring a Standard Project Flood would be sl ightly higher thanduring an Intermediate Regional Flood. Overbank flow in thestudy area would be less than 5 feet per second and averageabout foot per second. Water flowing at 2 feet per secondor less would deposit debris and si It.Rates of rise and duration of flooding - Intenserainfal Is that accompany hurricanes and other severe stormfronts usually produce the floods occurring in Sarasota County.Thus, with each hurricane that effects the study area, two typesof flooding occur, rainfall and tidal. Rainfal I type floodsgenerally rise slowly and stay out of banks for long periodsof time; whereas tidal type floods generally rise quickly andrecede quickly. For the Intermediate Regional and StandardProject Floods at South Creek, table 6 gives the maximum rateof rise, height of rise (from critical stage level to maximum,floodflow levell, time of rise (time period corresponding toheight of rise), and duration of critical stage (period of timeflooding is above critical stage level l.25.....•....-_._--------------------------