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<br />Green River Floodplain Inundation <br /> <br />14 <br /> <br />June 2005 <br /> <br /> 1800 100 <br /> . Area Inundated <br /> 1600 - Probability of Exceedance 90 <br /> . <br /> 1400 80 <br /> 70 Gl <br /> () <br />Ii 1200 c <br /> 1II <br />:S "CI <br /> . 60 Gl <br />"CI Gl <br />Gl 1000 . ~ <br />- <br />1II UJ <br />"CI . 50 It- <br />C 0 <br />::::l 800 ~ <br />.5 <br />1II 40 :c <br />e 1II <br /><C 600 .c <br /> 0 <br /> 30 ... <br /> Q. <br /> 400 20 <br /> Median historic <br /> regulated peak flow <br /> 200 . / 10 <br /> <br />o <br />o <br /> <br />100 <br /> <br />200 <br /> <br />300 <br /> <br />500 <br /> <br />600 <br /> <br />700 <br /> <br />o <br />800 <br /> <br />400 <br /> <br />Flow (m3/s) <br /> <br />Figure 4. The Relationship between Flow and Area of Inundated Priority Depression <br />Floodplain Habitat and the Probability of Exceedance for Flows under Historic Regulated <br />Conditions. Source: Muth et al. (2000) and Valdez and Nelson (2004). <br /> <br />4.2 Frequency of Connection to the Main Channel <br /> <br />It is hypothesized that razorback sucker larvae that are entrained into depression <br />floodplains benefit from remaining in those floodplain depressions until they become juveniles. <br />If this is true, it would be necessary to re-establish connections to floodplain depressions <br />frequently enough to provide juveniles with access back into the main channel. The optimal <br />frequency with which connection between floodplain depressions and the main channel should <br />occur is not currently known. However, it is probably desirable for connections to occur in most <br />years so that larval razorback suckers can be entrained into the d~pressions and so that juveniles <br />can return to the main channel as they mature. <br /> <br />The frequency with which a particular area becomes inundated is a function of the elevation of <br />the levees that separate the area from the main channel or a function of the design of gating <br />structures that are associated with some of the depression floodplains. To achieve inundation in <br />most years, the probability of exceeding the connecting flow level must be greater than 50% (one <br />in two years). Historically, the 50% exceedance level for unregulated instantaneous peak flows at <br />the Jensen gage was about 669 m3/s (23,625 cfs); the 50% exceedance level for regulated (post- <br />