With this option, the catchment storage exponent is entered directly or as a function of runoff, and will override the default value.
Normally this option can be ignored. It may be applicable on large river basins during extreme events. You could use this option, for example, to define a linear relationship between catcment storage and runoff, or to develop variations to the standard storage equation to match gauged results.
Storage Routing Exponent value. This exponent defines the non- linearity of the catchments response. The default is (-0.285). A value of (-0.001) will make the catchment response linear and act similarly to a unit hydrograph approach. At present a value of zero is not acceptable to the program. The default value is usually appropriate for inbank flows with the SRE moving towards -0.001 when large floodplain overflows occur. This means more frequent storm events say below 100yr return period can usually use the default value.
Values MUST be non-zero.
Three methods are presently available for the definition of this exponent.
- Use default value of -0.285.
- Enter a constant value of your choice.
- Enter a rating curve relating SRE to sub-catchment flow.