Soil Restoration and Erosion Control: Quantitative Assessment and Direction

Abstract

There are few statistically rigorous field evaluations of the performance of revegetation or soil restoration type erosion control efforts applied to steeper slopes associated with vineyards, rangelands, and disturbed soils (e.g., burns, roadcuts, and ski runs) in foothill or sub-alpine environments. Moreover, aside from the goal of runoff and sediment reduction, the particular treatment goal and functional duration in these environments is practically unknown, or unspecified. Information is also lacking on the runoff and erosion characteristics of less-disturbed range and forest soils that may help develop target restoration parameters. Erosion modeling using either Universal Soil Loss Equation (USLE) type erosion assessments or in Water Erosion Prediction Program (WEPP) type process models relies on laboratory, plot, and some field studies of erosion from bare to vegetated soils on relatively mild slopes. It is not clear how bare soil sediment transport processes can be realistically expanded to include those sediment control or filtration processes resulting from soil restoration efforts. Available predictions of erosion rates from partially rehabilitated or treated soils (e.g., grass covers, tillage, compost/mulch incorporation) are poor, due in part to limited data and understanding of the controlling factors affecting infiltration/runoff rates associated with the treatment. Present erosion control efforts often lack direction towards determination of the soil processes to be treated, changed, or restored such that runoff and erosion rates are effectively reduced. A new erosion control paradigm may be directed at restoring soil ecologic functioning. Gaining such information is crucial towards water quality modeling/monitoring and nonpoint pollution assessment associated with setting watershed Total Maximum Daily Loads (TMDLs) and represents a significant applied research opportunity.