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Title: Rainfall intensity and soil erosion by water : limitations of current erosion models and implications for erosion model-based studies under future climates
Author: Choi, Daniel Mintae
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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Existing simulation studies of the effects of future climate change upon erosion indicate that, under land usages that leave the soil unprotected, even minor increases in rainfall amounts are likely to result in disproportionately large increases in erosion, but commonly make the simplifying assumption that distributions of future rainfall intensities remain unchanged from the present. This research aims to determine implications of rainfall -intensity changes on soil erosion using computerised models. Thus, this thesis is a step towards the ultimate goal of predicting future rates of soil erosion caused by future rainfall intensity changes. Three soil erosion models, WEPP, EUROSEM, and RillGrow are employed to investigate impacts of various rainfall intensities on runoff and soil loss rates. Two extreme daily rainfall events in summer and autumn are subjectively selected from the tipping-bucket rainfall data, and runoff and soil losses are simulated using three erosion models. Estimated runoff and soil loss rates with high resolution rainfall data are greater than those with low temporal resolution rainfall data. Within-Storm Intensity Patterns (WSIPs) affect soil erosion amount, although runoff was not much affected. An additional daily rainfall event with Within-Storm Gaps (WSGs) is also selected to investigate effects of WSG removals on soil erosion. For a given amount of rainfall, events with constant low intensity (constant WSIP) produced dramatically less erosion: thus it appears that assuming a constant (or averaged) intensity throughout a storm does not provide a good representation of a real rainfall with its continuously varying intensity. Analyses of outputs from WEPP simulations revealed a problem that WEPP modifies original rainfall intensity and, thus, simulates erroneous runoff and erosion rates. Future soil erosion rates are estimated using WEPP and CLIGEN data. 30 year-long weather is generated by CLIGEN. Likely future rainfall frequency and intensity are anticipated by changing the mean maximum 30 minutes peak intensity also known as MX.SP. No fu ture rainfall amount change is assumed. WEPP simulation results suggest that where mean maximum 30-min peak intensity of the wet months increases soil erosion increases at a greater rate than runoff. This research assists in improving the performance of erosion models with respect to changes of rainfall intensity by highlighting where current problem exists. In conclusion, greater knowledge found here will, once future changes in rainfall intensity become better known and appropriate rainfall data become available, improve our ability to estimate future rates of erosion.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available