WSP06144

• File Number: 8210.470
• Description: Organizations - Pacific Southwest Inter-Agency Committee - PSIAC
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1968
• Author: PSIAC
• Title: Pacific Southwest Inter-Agency Committee - Report of the Water Management Subcommittee
• Water Supply Pro - Doc Type: Report/Study

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No rating influences the other factor ratings. Future conditions with
~ improved land use practices should not increase the rating. The
:: '--rating would be ~ecreased if the land will respond to proposed land
treatment pract1ces that would ~mprove the resource condition and
therefore decrease sediment yield potential. The rating would
remain the same if the present land use practices have stabilized
the land resources. The rating is cirri vedat by consultation
between'land use planners and technical specialist,s.

The Ground Cover (f) factor rating is modelled for the FWP
condition based on the anticipated impact of 'proposed 'Land Use (g)
practices. Greater vegetative ground cover created by increased
litter and/or.increased vegetation would lower the rating. A
degrading trend should not occur in theFWP condition. '

The Runoff (d) factor rating is modelled for the FWP condition
based on the increased ground cover and implementation, of
mechanical practices that increase surface roughness, retard flow,
and increase filtration. An increase in' Ground Cover (f) and
surface roughness would lower the rating. The rating could remain
the same as in the, Present condition if the proposed practices
would not significantly impact on runoff. '

The' Upland Erosion (h) factor rating is modelled for the FWP
condition based on the Runoff (d) and Ground Cover (f) ratings.
There would be less potential for concentrated overland flow
erosion if ground cover is increased and runoff is slowed.
Therefore, the rating would decrease. The factor rating could
remain the same as the Present condition if the there is no
significant impact on upland erosion due to the proposed land
treatment practices. "

The Channel Erosion and Sediment Transport (i) rating factor is
modelled for the FWP condition based on the UPland Erosion rating.
There would be a decrease in the rating if concentrated overland
flow and runoff was decreased. Therefore, gullies and channels
would support vegetation and stabilize.

SUMMARY AND CONCLUSIONS

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The proposed revisions of PSIAC would accomplish the following
goals: (1) update the procedure with recent research, (2) increase
the utility of the procedure in the field, (3) broaden the scope of
the procedure to include its use on geomorphic areas as well as
watersheds, (4) define the use of the procedure to characterize
future sediment yield rates for the present conditions continued
into the future and (5) define the use of the procedure to model
rates for various alternative future conditions involving proposed
land treatment planning measures.

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