University of Twente Student Theses


PCRGLOB-SET : development and verification of a global sediment supply model

Hoch, Jannis (2014) PCRGLOB-SET : development and verification of a global sediment supply model.

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Abstract:Sound knowledge of sediment transported along rivers and into the oceans is a relevant factor for the assessment of coastal erosion as well as for the maintenance of important ecosystems. Along with the increase of the World’s population, human actions have continuously impacted the detachment of soil and its transport towards the coast. The main interferences are the constructions of dams, the application of soil conservation practices as well as the intensification of land-use. In order to determine the global sediment flux into the oceans, models of soil erosion and sediment transport are needed. Therefore, the global sediment supply model PCRGLOB-SET has been developed. It is based on the RECODES model and uses equations of the RUSLE with some adaptions and extensions required for the large-scale application. The developed model is capable of producing monthly and annual output at a 0.5° grid cell resolution. Comparing the model output with observed values yields a coefficient of correlation of r=0.62. Thereby the main continental contributors of sediment into the oceans are correctly resembled with Asia delivering 41% of the global annual value. Since PCRGLOB-SET is a first-order model, it computes only unaffected sediment supply. The global annual sediment supply is determined to be between 150 GT/year and 195 GT/year which is, given the absence of important influences, a good estimate. The monthly output of PCRGLOB-SET has been compared to measured values in four river basins. Generally, the model is capable of representing the monthly fluctuations with most coefficients of correlation lying above 0.5. A sensitivity analysis revealed that the model output is less sensitive towards changes in the slope angle and temperature, but more sensitive towards variations in precipitation and vegetation cover. The intensity of these responses differs between continents. While precipitation changes strongly affect sediment supply in Africa while fluctuations of vegetation cover leads to considerable responses of computed sediment supply in South America. Model results are discussed in the light of model limitations such as the constricted representation of human influences and natural alluvial processes as well as in the model formulation. Eventhough these impacts cannot be explicitly quantified, it is concluded that PCRGLOB-SET provides a good starting point for further developments. In order to obtain more accurate results, it would be necessary to implement dams and reservoirs and to use a finer spatial resolution. Moreover, some equations applied in PCRGLOB-SET need to be tested more closely in order to apply them on the global scale. Nevertheless, the developed model shows potential for further improvements which are facilitated by the fact that the model has been coded in PCRaster which is a freely available and easily accessible tool for environmental modelling.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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