Spatio-temporal Variation of Suspended Sediment Sources in Rivers During High Flow Events
Abstract
In many rivers, natural suspended sediment (SS) transport dynamics have been disturbed due to human intervention within river channels and catchments. To develop sustainable, holistic management strategies, information is needed on the spatio-temporal variation of SS sources within catchments. In this study, sediment fingerprinting based on diffuse infrared Fourier transform spectrometry (DRIFTS) was used to investigate variations in SS sources during high river flow events and their relationship to hysteresis patterns and seasonal variations in SS concentration. A total of 200 suspended sediment samples were collected in the River Aire, UK, during 14 high flow events (2015-2017) and compared against five potential sediment sources: grassland topsoil in three lithologies (limestone, millstone grit and coal measures), urban street dust and eroding river channels. While limestone topsoil and urban street dust were the dominant sources of suspended sediment, temporal variation in sediment sources was observed. At the seasonal scale, urban street dust contribution was highest in summer (68% ± 10%) and lowest in autumn (35% ± 10%), while river channel contribution was lowest in summer (11% ± 18%). In autumn and winter, the combination of sediment sources was well-mixed. At the event scale, source contributions did not consistently follow the same hysteresis patterns. River channel contributions were observed during the falling limb of the flood hydrograph, while urban street dust remained relatively constant throughout events. Limestone grassland contributions decreased towards the end of events, especially when multiple events were in close succession, while millstone grassland slightly increased. These differences in temporal variation in sources are caused by the spatial distribution of sources, antecedent moisture conditions, and changes in sediment connectivity that control sediment supply and delivery to the river. While identifying dominant sediment sources is important to reduce SS concentrations in rivers, variations in sources over short to medium timescales provides insights into the factors driving SS transport and inform additional mitigation strategies that tackle high magnitude, but less frequent peaks in SS concentration.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP33C2427G
- Keywords:
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- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 1815 Erosion;
- HYDROLOGYDE: 1862 Sediment transport;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGY