High and Low Estimates of InfoSWMM/ICM Subcatchment Dimension for SWMM Hydrology

High and Low Estimates of InfoSWMM/ICM Subcatchment Dimension for SWMM Hydrology

These are the estimates for both SWMM 5, InfoSWMM and ICM SWMM Hydrology, the low estimate is 0.2*SQRT(Area in Feet) and the High Estimate is 5*SQRT(Area in Feet), Figure 1.  You can use higher or lower numbers to calibrate to monitored data but these are just guidelines using the InfoSWMM Subcatchment Manager Width Tool (Figure 2).

Table 1.  High and Low Estimates of the ICM Subcatchment Dimension for SWMM Hydrology or the SWMM 5 Subcatchment Width.

Subcatchment Area  (Acres)	Low Estimate  Width (Feet), W = 0.2*SQRT(Area)	High Estimate  Width (Feet), W =5*SQRT(Area)
1	41.74	1,043.55
5	93.34	2,333.45
10	132	3,300.00
25	208.71	5,217.76
50	295.16	7,379.02
100	417.42	10,435.52
200	590.32	14,758.05
300	722.99	18,074.84
400	834.84	20,871.03
500	933.38	23,334.52
600	1022.47	25,561.69
700	1104.39	27,609.78
800	1180.64	29,516.10
900	1252.26	31,306.55
1,000	1320	33,000.00
5,000	2951.61	73,790.24
10,000	4174.21	104,355.16
50,000	9333.81	233,345.24
100,000	13200	330,000.00

Figure 1  InfoSWMM Subcatchment Manager Width Estimator.