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Table Of Contents
Chapter 5 Working with Hydrology Commands
552
The remainder of the file, shown below, contains the tabular hydrograph unit
discharge data referred to as qt (for more information see page 5-2 of the TR-55
manual).
30,40,56,183,337,504,326,155,122,107,93,81,73,66,60,56,54,52,49
26,35,48,93,153,276,428,360,223,156,123,103,88,72,65,59,56,54,51
23,30,41,60,82,129,227,361,360,269,194,147,118,85,71,63,58,55,53
22,29,39,56,73,111,188,303,341,293,227,173,136,94,75,65,60,56,54
18,25,34,46,53,66,96,157,255,312,300,251,199,126,90,73,64,59,56
18,24,32,44,50,61,84,133,214,280,293,265,221,144,99,77,66,60,56
14,19,25,34,38,43,49,62,88,134,190,234,252,221,162,115,87,71,63
11,14,19,26,28,31,34,38,44,52,68,98,141,222,238,191,139,101,79
9,10,13,17,18,20,22,25,27,30,34,38,44,74,132,191,211,190,151,101
6,7,9,11,12,13,14,15,16,18,20,22,24,29,38,58,97,148,193,193,141
4,5,7,8,9,9,10,11,11,12,13,14,16,19,23,29,39,58,93,154,181,147,87
2,3,5,6,6,7,7,8,9,9,10,10,11,13,15,19,23,28,39,72,124,170,138,86
0,0,0,61,195,343,232,129,113,103,91,81,76,71,66,64,62,61,59,56,54
0,0,0,12,45,145,277,247,169,131,112,98,87,76,70,65,64,62,60,57,55
0,0,0,9,33,107,220,238,192,151,125,107,94,79,71,66,64,62,61,58,56
0,0,0,1,6,24,79,173,216,200,168,139,118,90,77,70,66,64,62,59,57,54
0,0,0,1,4,17,59,135,189,196,177,152,129,97,81,72,67,64,63,60,57,54
Selecting and Editing the Runoff Curve Numbers
for Different Soil Groups and Cover Types
Use the SCS Curve Number Editor to select and edit the runoff curve numbers
(CN) for various cover descriptions and soil groups. The CN values in the SCS
Curve Number Editor are obtained from the TR-55 manual. A curve number
expresses how much water will run off an area, based on soil and land use
conditions.
The TR-55 manual categorizes soils into four infiltration groups. Group A has
the fastest infiltration rate, while group D has the slowest. The U.S. Soils Survey
map of your site shows specific soil types with codes. Appendix A of the TR-55
manual shows the absorption group for each soil type on the US Soils Survey.
All the curve numbers for hydrologic soil groups A, B, C, and D are already
input and stored in the runoff.cof file in the c:\Program Files\Land Desktop
R2\land\prot\hd folder. You can use the SCS Curve Number Editor command
or any text editor to edit this file.
NOTE
The Runoff Curve Number Editor is available directly from the Runoff menu
(as described in step 1 below), or from the TR-55 Graphical Peak Discharge
Method dialog box, the TR-55 Tabular Hydrograph Method dialog box,
and the SCS TR-20 Unit Hydrograph Method dialog box.