Evidence of non-contiguous flood driven coarse sediment transfer and implications for sediment management

Heritage, G; Entwistle, NS; Milan, D

Abstract

We investigate gravel redistribution and morphological response of three headwater streams following the Storm
Desmond floods of December 2015. Reactive management of the watercourses following the flooding
concentrated on removal of gravel and clearing of vegetation, perceived as having been significant causes of
local flooding. Aerial LIDAR and ortho-photography were employed to critically assess the location, type and
magnitude of sediment mobilization, using an sUAV to capture imagery of lake sediment fans across the area.
Whilst gravel was mobilized during the flood the volumes involved do not appear to be as high as anticipated,
with little detectable change in lake fan deposits in the sink zone of the three study streams. Re-exposure of
relict gravels on floodplains through stripping of surface vegetation and soils, gave the false impression of fresh
deposition. Reactivation of wandering channel zones appear to have acted as buffers to large-scale sediment
movement rather than acting as supply zones. Sediment accumulation through towns and villages was harder
to quantify due to the rapid clean-up operation, however, the authors suggest that this may not be as large as
assumed and the widespread dredging is likely to have caused more problems than it has solved as the bed of
many watercourses is now highly susceptible to mobilisation following mechanical disruption of the previously
strongly armoured surface.

Citation

Heritage, G., Entwistle, N., & Milan, D. (2019, September). Evidence of non-contiguous flood driven coarse sediment transfer and implications for sediment management. Presented at 38th IAHR World Congress, Panama City, Panama

• Presentation Conference Type: Other
• Conference Name: 38th IAHR World Congress
• Conference Location: Panama City, Panama
• Start Date: Sep 1, 2019
• End Date: Sep 6, 2019
• Acceptance Date: Jul 15, 2019
• Online Publication Date: Sep 1, 2019
• Publication Date: Sep 1, 2019
• Deposit Date: Nov 14, 2019
• DOI: https://doi.org/10.3850/38WC092019-1733
• Publisher URL: http://iahrworldcongress.org/
• Additional Information: Event Type : Conference