FLOOD05030 - Laserfiche WebLink

Home Browse Search

INVESTIGATIONS AND ANALYSIS Interpretation and Use of Report A. Frequency and Discharge The 10-, 50-, 100-, and 500-ye~r fl ood events are used as the t1 oOd frequencies for this flOOd plain analysis, Thus, the data developed in this report wi 11 be suitable not only for reg~latjon purposes, and H.B. 1041 destgnationbutalsoforFederal lnsuranceAdministrationflood ins~rance studies co~d~cted by the Federal Emergency Management Agency. These ~arious flood events ha~e an average occurrence of once in the numb~r of years as indicated. For e~ample, the 100_y~ar flOOd occurs, on the average, once in a lOa-year period, and has a one percent chance of being equaled or exceeded in any given year. The particular uses for the various flood events in addition to tho se stated above are as fOllows: lO_Year and 50.Year Flood Events lnformation regdrding these lower frequency floods is especially useful for future engineering studies and land use planning purposes related to minor road systems, minor channel improvements, the location of par~s and recreational facil it ies, agricultural lands, and appurtenant structures. The use of the lower frequencey floods may be considered in pl anni ng fl Ood prev~nt i on projects to protect agri cul tura 1 dr,,~~, or other property w~ere risk to life is not a factor. laO-Year Flood Event The IOO-year flood event may be used in lieu of lower frequencies for engi neering design purposes where greater s~curi ty from structure fai lure is desired. However, the most important use of the lOa-year flOOd event lies i~ flood plalnmanagelTlent and land use planning as set forth in the sta te statutes, The State of ColoradO considers the 100-year frequency flOOd as the flOOd event to be used in desig1ing and protecting structures and dwellings for human occupation. Therefore, all flood plain regulations are based upon the lOO.year flood, 500-Year Flood Event The 500-year flood event is useful in making the public aware that floods larger than the laO-year flOOd can and do occur. Just because a person is l1ving above the laO-year flood boundary does not mean that he is completely safe from flooding. The 500-year flood event can also be used for regulating high risk developments within the flood plain such as nuclear power plants, or the storage or manufacture of toxic or explosive mdterials. B. FlOOd Elevation Floodcreste1evdtions fortne10-, 50-, 100-, anct 500-year floOdS, as determined at edch cross section, may be found in Table 1 "Flood Frequency-Elevation and DischugeData", Flyures, 1 through 5, show a graphical representation of high water elevations at typical valley cross sections. Water surface elevations computed at each cross section were used to prepare flood profiles, sheets 1 through 23, which ShOw the streambed elevation in relation to ~ater surface elevations for the 10-, 50-, 100-, and 500-year frequency floods. The flOOd profiles may be used in areas where controversy arises over the laO-year flood boundary s~own on the FlOOd Plain Maps. Since the flood profile e~hihits give the water surface elevation at ~ specific -11- -12-