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<br />, <br /> <br />area ~bove Two Forks. If the extent 9f each of two groups was about <br /> <br />equal, like weight was assigned to each' group. The percent of each <br /> <br />major type of land use within each of these subareas wo?s' also deter- <br /> <br />mined, These data were assembled and a curve number (CN) for ante- <br /> <br />cedent moisture condition II assigned for each land use type and <br /> <br />respective hydrologic soil gro~p using Table A-2, Design of Small <br /> <br />Dams, 2d Edition, page 536. A subarea CN for each subarea was com- <br /> <br />puted using the percentage of type land use as weights, A curve number <br /> <br />common to similar subareas was selected for use on the basis of close <br />of <br />agreement/computed numbers and a judicious slight reduction for the <br /> <br />large amount of ponding area observed during the field inspection <br /> <br />trips. Curve No. 65 was selected from Table A-3, DSD,2d Ed., as <br /> <br />applic~ble to all subareas designated MD. A minimum constant loss <br /> <br />rate of 0.20 inch per hour was selected applicable for subareas MD. <br /> <br />Minim~ loss rates selected for the other subareas varied depending on <br /> <br />dominant hydrologic soil group and land usage. A list of the curve <br /> <br />numbers and minimum loss rates used for each subarea is given in <br /> <br />attached Table A-4. <br /> <br />.A simplified approach was used to obtain the amount of runoff from the <br /> <br /> <br />area above Two Forks damsite. 'the rainflood portion of the 1966 IDF <br /> <br />hydrograph for the damsite was isolated and the volume computed as <br /> <br />3.17 inches for the total area of 2,585 square miles. Design storm <br /> <br />values for each of four subbasins were used in the 1966 study. <br /> <br />Excess precipitation occurred during. the maximum 24-hour period of <br /> <br />the storm. A total basin average 24-hour, depth-duration value of <br /> <br />17 <br /> <br />...;.;,.., <br /> <br />._~"'" -~ ~.~. , <br /> <br />,,0' ,,,~_._ <br /> <br />.., ..i..,.~,\,. .... .,...a;..........'>II'"..t__._:..~~~ _~.,. ,~.~~.~ .'.~ <br /> <br />'1lI""1 <br /> <br />. <br />