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<br />EM 1110-2-1405 <br />App IV <br />31 Aug 5' <br /> <br />e <br /> <br />DRAINAGE AREA CHARACTERISTICS FOR PERTINENT DATA SHEET <br />(ENG, FORM 1821) <br /> <br />Drainage Area: The contributing basin area. in square <br />miles above a specified location. <br />Maximum Elevation: Maximum elevation of topography <br />in the drainage basin, <br />Minimum Elevation: Minimum elevation of topography <br />in the drainage basin. <br />~.{ean Elevation: Weighted elevation of basin surface, <br />determined by integration of area-elevation curve, <br />Land Slope: The slope of the ground surface to stream <br />channels. The "intersection-line method" as proposed by <br />Robert E. Horton in an article titled .. Drainage Basin <br />Characteristics," Trans, American Geophysical Union, <br />1932, has been found to give reasonable values with the <br />least amount of labor. An e.-..:ample of this procedure will <br />also be found in U.S. Geological Survey, Dept. of Interior, <br />publication WSP 968-C titled "Topographic Character- <br />istics of Drainage Ba:;;ins," <br />L: Total length of longest watercourse. <br />Lea: Distance along the main drainage channel from <br />gage to computed center of gravity (centroid) of drainage <br />area, obtained by integration of area-distance curve <br />divided by the drainage area. <br />(LLe..).3: Self explanatory. <br />Drainage Density: Total length of all watercourses <br />shown in the basin (full and dashed bluc lines on U .S.G .S. <br />quadrangle maps) divided by the drainage area, <br />Map Scale: Scale of map used in determining drainage <br />characteristics, <br />Flow Separation: <br /> <br />Type A straight line base flow <br />Type B convex base flow <br />Type C concave base flow <br /> <br />Basin Shape Factor: = J:A <br /> <br />Profile: Line joining points of channel elevation of <br />longest watercourse at corresponding distances from the <br />gage. <br />Area-Elevation Curve: Line joining values of area <br />above the corresponding specified elevation. <br /> <br />Area-Distance Curve: Line joining values of contributing <br />area at corresponding specified distances from gage. <br />Main Stream Slopc: It is the slope of an equivalent <br />stream which has the same length as the natural longest <br />watercourse, and an equivalent time of travel. <br /> <br />S"~[ ~J' <br />vS. <br /> <br />where <br /> <br />S.j=main stream sIO!Jt; <br /> <br />n=number of equal increments of the longest water- <br />course <br /> <br />Si=slope of channel increment in feet per foot. <br /> <br />For derivation of the slope equation f>CC papcr by <br />Arnold B. Taylor and Harry K Schwarz, "Unit hydrograph <br />log and peak flow related to basin charactcristic~," <br />Trans., Am. Geophy. Union, Vol. 33, 1952, pp. 235~2-1-6. <br /> <br />Example: Evitts Creek. e <br /> lncr. of ~S; 1 <br />Elevation Elevation L S. ~S; <br />feet feet feet It.llt. <br />1022 <br />1070 48 6330 0.0076 O. 087 11. 50 <br />1110 40 6330 .0063 .079 12. 70 <br />1140 30 6330 .0047 .069 14.50 <br />1154 14 63:30 .0022 ,047 21. 20 <br />1170 16 6:l30 .0025 .050 20.00 <br />1205 35 6:3:30 .0055 .074 1:3.50 <br />1235 :30 6:3:30 ,0048 .069 14.50 <br />1420 185 63:30 .0292 . 171 5, 85 <br />1670 250 6:330 ,0:395 .198 5.05 <br />2580 910 6330 .1439 .379 2.64 <br /> <br />121. 44 <br /> <br />[ 10 ]' . <br />S..= 121.44 ~O,0823'~0.00677 ft./lt.~:35 It'/ml. <br /> <br />PLATE NO. 17 (Sheet 201:3) <br /> <br />56 <br /> <br />e <br />