View Full Version : Build up and Washoff parameters

March 4, 2015, 05:39 PM
Hi all, we are trying to model a big catchment with various landuses, we are interested in the final deposition of sediment/grit in the pipes. We won't use pollutant graphs, we plan to enter the pollutants though pollution indexes which are associated to landuses. Can anyone please advise when I can find any table containing the buildup and wash-off parameters for various landuses such as residential, commercial, etc?
Many thanks

Duncan Kitts
March 6, 2015, 03:59 AM
The model is made up of 2 parts the sediment build-up and the erosion parameters:-

The build-up requires a build-up decay factor and a surface build-up factor.

The build -up decay factor defines the build-up of sediment upon the surface. The default value is 0.08, the smaller the number the quicker the build up rate. The help page 'Surface Pollutant Build up' contains some typical surface build-up factors for different land surfaces.

Land Use Surface Buildup Factor (kg/ha/day)
Residential (Dense) 25
Residential 6
Town Centre (commercial) 25
Industrial 35
Mixed Suburban 6

The erosion requires the specification of 3 erosion calibration coefficients. I'm not aware of any typical values for specific surfaces.

March 11, 2015, 01:24 PM
Hello Duncan
Thanks for your previous reply, I'm using the parameters that you recommended.
We are designing a 2.5m diameter pipe in a large urban catchment, we want to minimise the amount of
grit deposited in the pipe. My understanding is that "Concentration SF1" is the
"SUSPENDED" concentration of sediment fraction 1, is that right? how do I enquire
Infoworks to give me BED load and DEPOSITED load? Ult
Christian Aranibar