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<br />OOlG80 <br /> <br />32.8--6 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HAND~OOK <br /> <br />difference in time increments, converted to days, between the last <br />rise-recession step and the QLl/QB time scale intersection points. <br /> <br />The QL2/QB ratio point, the lowest flow (highest exceedance value) on '. <br />the fTow-duration curve, is used to estimate the amount of low-flow that. <br />may occur during the remaining time increment (i.e., from the QLI/QB <br />.intersection point to the end of the time scale). The required basef10w is <br />QLI or the natural flow whichever is the lesser. The QL2 flow rate and <br />duration are computed only for the purpose of estimating the total low-flow <br />volume contained in the flow component which is less than basef10w. <br /> <br />Common Step 4 - Using local data and professional judgement determine if <br />additional flows are needed to prevent vegetation encroachment. . . <br /> <br />If in the user's professional judgement the potential for vegetation <br />encroachment is low, proceed to Common Step 8. If potential for vegetation <br />growth between the top of the inner berm and the start of the channel b,nks <br />is high, quantify the necessary flows utilizing Common Steps 5 through 7. <br />Base the assessment of vegetation growth potential upon the following: <br /> <br />I. The type and size of channel materials. <br /> <br />2. The availability of seed sources or likelihood of vegetative <br />sprout i ng. <br /> <br />3. The length of growing season during which this portion of the <br />channel is not inundated. <br /> <br />4. The availability of non-channel water sources capable of <br />supporting vegetation. <br /> <br />5. The water storage capacity of streamside substrate. <br /> <br />6. The shape of the channel cross-section. . For example, a large <br />width/depth ratio (shallow, wide channel) has higher potential than one <br />with a small width/depth ratio (narrow, deep channel) as in 1 and 2 below. <br /> <br />1. <br /> <br />HIIM ~T["TIAL 'OR <br />YEnTA"1 ENC~_ TO' or ACTlYE CHANNEL <br /> <br />'- . I _ _ . CHAHNI!:~ ....NIeS <br /> <br />~ LOW 'LOW CHANNEL <br /> <br />2. <br /> <br />LOW fllOTENTIAL 'OR <br />vEGETATION (NCltOACHIIENT <br /> <br /> <br />. <br /> <br />TO" Of' ACTIVE CHANNEL <br /> <br />CHANNEL IANICS <br /> <br />LOW 'LOW CHANNEL <br />