Pacific Southwest Research Station

Development of a Road Cut and Fill Land Use Category for the Pollutant Load Reduction Model (PLRM)

Full title: Development of a road cut and fill land use category for the Pollutant Load Reduction Model (PLRM)

Lead Researchers: Mark Grismer and Michael Hogan, Integrated Environmental Restoration Services

Abstract

Recent modeling conducted as part of the Lake Tahoe Total Maximum Daily Load (TMDL) planning effort suggests that 72% of the fine sediment load (< 20-micron) to Lake Tahoe originates from urban upland source areas. The Pollutant Load Reduction Model (PLRM) is the primary modeling tool being developed to support landowners in urbanized watershed areas in identifying sources of pollutant loading, prioritizing and implementing projects to reduce pollutant loading (primarily fine sediment), and determining post-implementation load reductions from various projects. The current PLRM generalizes the pollutant loading characteristics of both paved road surfaces and adjacent cut and fill slopes in a single "roads" land use category, which is both misleading and inaccurate. However, the PLRM was specifically designed to incorporate new land uses as new data becomes available. This project will leverage the most complete set of directly measured erosion data in this region and conducted targeted rainfall simulation to develop a new land use category for road cut and full slopes. Additionally, using quantitative data and input from agency personnel, this project will define functional condition classes and develop a straight-forward field protocol that regulators and project implementers can use to identify and classify the pollutant loading potential of cut and fill slopes at the project scale.