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<br />6 <br /> <br />basin storage, will influence floods. These factors are primarily <br /> <br />climatic, botanic, and geologic 'in nature (Norisawe, 1968, p, '16), <br /> <br />Climatic conditions preceding and during a storm will in- <br /> <br />fluence the amount and rate of runoff, Several days of rain will <br /> <br />seturate ba,sin storage and all the subsequent rainfall must run off, <br /> <br />Hail that precedes cloudbursts packs the ground and decreases infil- <br /> <br />tration into the soil, causing rapid runoff. <br /> <br />Botanical factors th~t influence flooding are the amount and <br /> <br />type of vegetation. Vegetation transpires and promotes the evapora- <br /> <br />tion of water that enters a basin, affecting a decrease in total <br /> <br />runoff. Plants promote'infiltration by ponding water and breaking <br /> <br />up the soil. Different kinds and densities of vegetation effect <br /> <br />total rurtoff and rate of runoff to various, degrees. <br /> <br />The major geologic factors th~t influence flo~ding are' soil <br /> <br />texture and structure, basin s'ize, shape and slope; bedrock perme- <br /> <br />,ability; and channel size, shape,-roughness and gradient.' Soils <br /> <br />with low porosity and permeabi.lity increase runoff. Luge basins <br /> <br />gather large amounts of water, so they tend to have correspondingly <br /> <br />large peak flows. Steeply dipping basins cause rapid runoff, In <br /> <br />circular basins, tributaries feed' into main streams at nearly the <br /> <br />same time and produce large, ,brief peak flows. Bedrock permeability' <br /> <br />determines infiltration rate after the overlying soil is saturated. <br /> <br />The channel characteristics determine the quantity of water that it <br /> <br />can carry. \~len that quantity is exceeded, the channel'floods. <br /> <br />Development within a basin will often dra~atically increase <br /> <br />the amount and rate of runoff (Leopold, 1968, p. 2) and hence <br />