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All Topics | Topic "Runoff Resistance Factor (rrf) And Manning's N"
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Author Message
Patrick Keys

Subject: Runoff Resistance Factor (rrf) And Manning's N   
Posted: 4/6/2010 Viewed: 11909 times
Hi,

Does anyone know of a relationship between the Runoff Resistance Factor (RRF) and the surface roughness coefficient, Manning's N? I am trying to estimate the RRF of a landcover dataset, and it would be handy to have a conversion factor or coefficient by which to multiply standardized roughness values to find RRF.

If not, maybe this is a niche for some research?

Thanks,
Pat
Glenn Moeller

Subject: Re: Runoff Resistance Factor (rrf) And Manning's N   
Posted: 4/19/2010 Viewed: 11842 times
Hi Patrick,

RRF (formerly Leaf Area Index, LAI) is more akin to C in the rational formula than to Manning's N. Increasing RRF causes a decrease in surface runoff (since Z1 is less than 1 and surface runoff of proportional to Z1 raised to the RRF) with a consequent increase in Z1. This of course leads to higher interflow, Z2 (or flow to GW), baseflow, and ET. I'm not sure how you're trying to use N in WEAP, but I do not believe this is the way to do it. I'm not actually sure it can be done at all.

Hope this helps,
Glenn
Gonzalo Cortes

Subject: Re: Runoff Resistance Factor (rrf) And Manning's N   
Posted: 5/5/2010 Viewed: 11791 times
Hi Patrick, I think it should be a mistake associating N in any way with WEAP. Manning's n is more of an "hydraulic" property of a channel, and it should be considered only if you're interested in properties of the water flow inside the channel, such as speed and height of the flow. As WEAP21 doesn't compute or use this values, Manning's N should be of no importance in our data.


Topic "Runoff Resistance Factor (rrf) And Manning's N"