Calculation method of catchment area feature width

In the SWMM model, one of the most important parameters is the feature width of sub-catchment area (width), which has a certain effect on the time and peak of the surface confluence. There are many methods to calculate the feature width of sub-catchment area, here are two common types:

(1) The method of dividing the area by the length of the flow: the length of the stream can be assumed to be the distance from the farthest point of the sub-catchment area to the exit of the sub-catchment area, and then the feature width is obtained by dividing the area of the sub-catchment area by the length of the stream. The flow length can also be approximate method, such as the boundary on the farthest from the exit of a vertex to calculate the length of the flow, so that the GIS can be extracted from the sub-catchment area of the vertex, and then a simple calculation will be able to get the flow length. (Common method)

(2) The method of using an area radical: This method is relatively simple, the sub-catchment area is approximate to a rectangle, assuming that the feature width is the square root of the area. Some people in the calculation also in the square root superior to a factor, this may have some reason, but whether the significance is debatable, and how this coefficient is also a problem.

As for other methods, such as the circumference of the sub-catchment area or the length and width multiplied by a factor to calculate the feature width, the method is relatively simple, not described here. No matter what calculation method is used, the feature width should be less affected by the result if it is within reasonable range.

Calculation method of catchment area feature width