For RouteChannel command, there is an extra tabs called Erosion Indices for Continuous project. The Erosion Indices compares RouteChannel results in three erosion indices: Time of Exceedance, Cumulative Erosion Index and Cumulative Effective Work Index. Before doing the comparison, users should also assign the pre-development scenario as described above. Open the Scenario Comparison and choose RouteChannel command. Click on the Erosion Indices tab. In the drop-down window of Type, choose one index from the three erosion indices to be compared. Type the parameters and click Update. The Graph and the Statistics table will be updated.
Please note that it may take a while to show the results of Cumulative Effective Work Index.
Calculation method and user input parameters required for each index:
Time of Exceedance:
Time of Exceedance is to count the hours when the channel velocity is higher than the Critical Velocity. Critical Velocity is a user’s input parameter.
Cumulative Erosion Index:
where, is the user-defined Critical Velocity, and is Velocity in the channel.
Cumulative Effective Work Index:
where, C is a user-defined Coefficient, is a user-defined Critical Shear Stress, is Velocity in the channel, is the Water Depth in the channel, S is Channel Slope, is Water Density, and is Gravity Constant Value.