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<br />/' <br /> <br />Evaporation <br /> <br /> <br />( <br /> <br />~ <br />I" "'-.. <br />C_ _ --===- <br />Ili'I:::!I:! .. <br />':';i:'I'I.ij <br />I'; :: <br />I Ii; ': ! ( <br />:1 I <br />Precipitation <br /> <br /> <br />The hydrologic cycle con- <br />stantly circulates water <br />throughout the earths en, <br />l/ironmenl. <br /> <br />The riverine watershed is <br />a hierarchical drainage <br />system tbat conveys water <br />through the land-hased <br />portion of the hydrologic <br />cycle. <br /> <br /> <br />A Rills <br />B Creeks <br />C Rivers <br /> <br />10 <br /> <br />. <br /> <br />~ <br /> <br />I <br /> <br />I <br />J <br /> <br />~ <br />c <br />.y <br />~ <br />~ <br /> <br /> <br />r <br /> <br />~ <br />~ <br />z <br /> <br />habitation. To better understand this problem we look <br />first at the l1alUfal system of which flooding is a part <br /> <br />The Hydrologic Cycle <br />Flooding is part of the earth's natural hydrologic cycle <br />The cycle circulates water through a process of evapora- <br />tion and transpiration, precipitation, water runof( and <br />stream flow This process maintains an overall global hal. <br />anee between atmospheric moisture and water on the <br />surface and in the grouml Oftel\ however, iocai imb,ll- <br />ances result in flooding. <br />Flooding results when the flow of water is greater <br />than the normal carrying capacity of a stream, or where <br />coa"tal waters exceed the normal high tide. This raises an <br />important distinaion bct\veen riverine and coastal tlood- <br />ing; though both are part of the global hydrologic system, <br />the re.spective causes are dissimilar Rivers flood when <br />water overflo\vs the channel because of excessive water <br />runoff or blockage of the channel. Coastai flooding resuits <br />from high ,vater produced by storm systems or tsunamis <br />(seismic sea waves). <br /> <br />Riverine Flooding <br />The magnitude, duration, and frequency of flooels are <br />intluenced by a region's natural charaacristics. One pri- <br />