English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Simulation of upland-soil erosion by the Precipitation-Runoff Modeling System currently requires the user to estimate two rainfall detachment parameters and three hydraulic detachment parameters. One rainfall detachment parameter can be estimated from rainfall simulator tests. A reformulation of the rainfall detachment equation allows the second parameter to be computed directly. The three hydraulic detachment parameters consist of one exponent and two coefficients. The initial value of the exponent is generally set equal to 1.5. The two coefficients are functions of the soil's resistance to erosion and one of the two also accounts for sediment delivery processes not simulated in the model. Initial estimates of these parameters can be derived from other modeling studies or from published empirical relations. INTRODUCTION Simulation of upland soil erosion by the Precipitation-Runoff Modeling System (PRMS) currently requires the user to estimate two rainfall detachment parameters and three hydraulic detachment parameters (Leavesley and others, 1983). At present, these five parameters must be estimated by calibrating simulated results with observed data collected either on small upland plots or at a downstream gaging station. Neither method provides a physical basis for estimating or transferring parameter values. To provide a starting point for further research on the physical basis and significance of these parameters, a preliminary assessment of the status of upland soil erosion research and modeling has been conducted. Recent literature on the subject has been reviewed and research personnel who are actively investigating upland soil erosion have been contacted during this study. The most significant progress in relating measurable soil properties to modeling parameters has come from agricultural research. Studies involving rainfall simulators have shown that some rainfall detachment parameters can be related to drop size distribution, fall velocities, and total mass at impact (Hudson, 1971). Hydraulic detachment parameters have been found to be a function of certain physio-chemical properties of the soil which influence the material's resistance to erosion. These properties have been found to include particle size, cation-exchange capacity, percentage organic matter, sodium adsorption ratio (SAR), dissolved solids concentration in pore water, and temperature (Partheniades, 1965; Sherard and others, 1972; and Sargunam and others, 1973; Ariathurai and Arulanandan, 1978; Kelly and Gularte, 1981). Site specific factors such as soil density, antecedent moisture, particle orientation, previous stress history, and initial state of compaction have also been found to exert significant influences on the erosion of cohesive soil material (Grissinger, 1966) . The influence of cohesive forces relative to gravitational forces in a soil determines the significance of the physio-chemical properties in parameter evaluation. As yet, no single or combined set of analyses have been shown to yield consistently accurate estimates of parameter values over a wide range of cohesive conditions. The methods presented in this report provide guides to estimating initial parameter values. These values are only estimates and the model user should not hesitate to adjust or replace these initial values in favor of reasonable values that improve model results.

Physical basis and potential estimation techniques for soil erosion parameters in the Precipitation-Runoff Modeling System (PRMS)