Laserfiche WebLink
<br />affected streams rise relatively slowly over a period of several <br />days. The duration of the flood period can also be of consider- <br />able length. <br /> <br />Erosive effects can be considerable in the event of any flood <br />regardless of its origin. Floods resulting from intense <br />rainstorms typically create severe erosion damages in a short <br />period of time due to the floodwater's relatively large peak <br />discharge and high velocity. Typically, erosion damages from <br />snowmelt or general rainstorm floods usually result from <br />prolonged flooding. <br /> <br />2.4 Flood Protection Measures <br /> <br />The Town of Sedgwick presently has no flood protection measures <br />within the corporate limits. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />For the flooding sources studied by detailed methods in the community, <br />standard hydrologic and hydraulic study methods were used to determine <br />the flood hazard data required for tbis study. Flood events of a <br />magnitude which are expected to be equaled or exceeded once on the <br />average during any 10-, 50-,and 100-year period (recurrence interval) <br />have been selected as having special significance for floodplain <br />management and for flood insurance rates. These events, commonly <br />termed the 10-, 50-,and 100-year floods, have a 10-, 2-, and I-percent <br />chance, respectively, of being equaled or exceeded during any year. <br />Although the recurrence interval represents the long-term average <br />period between floods of a specific magnitude, rare floods could occur <br />at short intervals or even within the same year. The risk of <br />experiencing a rare flood increases when periods greater than one year <br />are considered. For example, the risk of having a flood which equals <br />or exceeds the IOO-year flood (I-percent chance of annual exceedence) <br />in any 50-year period is approximately 40 percent (4 in 10), and, for <br />any gO-year period, the risk increases to approximately 60 percent (6 <br />in 10). The analyses reported herein reflect flooding potentials <br />based on conditions existing in the community at the time of <br />completion of this study. Maps and flood elevations will be amended <br />periodically to reflect future changes. <br /> <br />3.1 Hydrologic Analyses <br /> <br />Hydrologic analyses were carried out to establish the <br />discharge-frequency relationships for each flooding <br />studied by detailed methods affecting the community. <br /> <br />peak <br />source <br /> <br />Peak discharge-drainage area relationships for the South Platte <br />River are shown in Table 1. <br /> <br />4 <br />