Effects of the anthropogenic landscape on global suspended sediment flux

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University of Alabama Libraries

Human industry and agriculture have long-term effects on the erosion and transport of sediment from the continental surface to the ocean. Riverine suspended sediment flux can be increased where soils are exposed to erosion but can also be trapped behind reservoirs or under impervious surfaces. Literature examining the effects of anthropogenic land-use and disturbance on suspended sediment flux are generally limited to individual reaches, streams, or basins. This thesis describes and analyzes the first global-scale and spatially-explicit model simulating the effect of anthropogenic land-use on suspended sediment flux. Quantifying suspended sediment flux at the global scale is complicated by the limited extent of gaging stations and observed datasets. Modeling provides a pathway which allows researchers to investigate the flux of sediment from the terrestrial environment to the coastal ocean where there is a lack of observed records. Anthropogenic land-use effects on global suspended sediment flux are investigated here by incorporating a new spatially and temporally explicit parameter in the WBMsed model, a global-scale riverine modeling framework. A new anthropogenic factor (Ad) is developed and validated for the WBMsed model. Ad is created from readily available and regularly updated land-use/land-cover datasets and used to calculate the effect of land-use in a spatially and temporally explicit manner. The results of the model validation show that incorporating Ad into WBMsed increases intra-basin variability of suspended sediment flux predictions. The Ad parameter also has the effect of increasing the model's relative accuracy with observed long-term suspended sediment records in streams with smaller drainage areas. Following the validation of the Ad factor in WBMsed, we analyze the anthropogenic contribution to global suspended sediment flux. Our results show that although anthropogenic disturbance increases overall suspended sediment flux on every continent, this signal is masked by the mitigating effect of reservoir trapping of sediment. By isolating sediment trapping and land-use effects, the global-scale, spatially-explicit quantification of anthropogenically contributed suspended sediment is provided.

Electronic Thesis or Dissertation