Monitoring & modelling fluvial hydrogeomorphic response to leaky wooden dams

Wolstenholme, Joshua Matthew

Abstract

The introduction of large wood to fluvial systems is an increasingly popular method of natural flood management (NFM). Leaky dams (LDs) are designed to attenuate the hydrograph and ‘slow-the-flow’, intercepting high flows, and providing temporary storage within the river channel and on the floodplain. However, LDs may store sediment, potentially impeding their ability to reduce flood risk after one or more storm events. Despite this, the majority of NFM and LD numerical modelling does not consider sediment transport, often only considers a single storm event, and is performed in reaches or catchments smaller than 10 km2.
This research employed a combined field and numerical modelling approach to explore the impact of LD on fluvial geomorphology from the unit to reach to catchment scale. Topographic surveys of a field site in a 32.2 km2 catchment in Dalby Forest, North Yorkshire, were used to generate Digital Elevation Models (DEMs) and DEMs of Difference to quantify the volumetric change associated with the installation of LDs of different designs and relative spacings over a 3.5-year period. Using the new ‘Working with Natural Processes’ toolbox developed for CAESAR-Lisflood for the first time, the influence of LD design and installation location on sediment transport and geomorphic change throughout an experimental reach and catchment was assessed in response to multiple storm types. Additionally, the response to future climate was tested, accounting for increased winter storms and decreased rainfall during the summer to identify the potential future efficacy of LDs to a changing climate.
Results suggest that the nested hydrogeomorphologic processes at work within river catchments, particularly those related to bed scour, sediment transport and deposition, and the associated feedbacks following implementation of LDs substantially impact water storage within the system, as well as effectively reduce flood peaks when distributed throughout a catchment.

Citation

Wolstenholme, J. M. Monitoring & modelling fluvial hydrogeomorphic response to leaky wooden dams. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4436310

• Thesis Type: Thesis
• Deposit Date: Nov 10, 2023
• Publicly Available Date: Jul 2, 2026
• Keywords: Geography; Environment
• Public URL: https://hull-repository.worktribe.com/output/4436310
• Additional Information: Department of Geography and Environment; University of Hull
• Award Date: Sep 26, 2023