Preprints
https://doi.org/10.5194/egusphere-2024-2132
https://doi.org/10.5194/egusphere-2024-2132
30 Aug 2024
 | 30 Aug 2024

Hydro-geomorphological modelling of leaky wooden dam efficacy from reach to catchment scale with CAESAR-Lisflood 1.9j

Joshua M. Wolstenholme, Christopher J. Skinner, David J. Milan, Robert E. Thomas, and Daniel R. Parsons

Abstract. Leaky wooden dams are woody structures installed in headwater streams that aim to reduce downstream flood risk through increasing in-channel roughness and decreasing river longitudinal connectivity in order to desynchronise flood peaks within catchments. Hydrological modelling of these structures omits sediment transport processes since the impact of these processes on flow routing is considered negligible in comparison to in-stream hydraulics. Such processes are also excluded on the grounds of computational expense. Here we present a study that advances our ability to model leaky wooden dams through a roughness-based representation in the landscape evolution model CAESAR-Lisflood, introducing a flexible and representative approach to simulating the impact of leaky wooden dams on reach and broader catchment-scale processes. The hydrological and geomorphological sensitivity of the model is tested against grid resolution as well as a variability in key parameters such as leaky dam gap size and roughness. The influence of these parameters are also tested in isolation from grid resolution, whilst evaluating the impact of simulating sediment transport on computational expense, model domain outputs and internal geomorphological evolution. The findings show that simulating sediment transport increased the volume of water stored in the test reach by up to an order of magnitude whilst reducing discharge by up to 31 % during a storm event. We demonstrate how this is due to the leaky dam acting to induce geomorphic change and thus increasing channel roughness. When considering larger grid resolutions, however, our results show that care must be due to overestimations of localised scour and deposition in the model and that behavioural approaches should be adopted when using CAESAR-Lisflood in the absence of robust empirical validation data.

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Joshua M. Wolstenholme, Christopher J. Skinner, David J. Milan, Robert E. Thomas, and Daniel R. Parsons

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2132', Anonymous Referee #1, 27 Sep 2024
  • RC2: 'Comment on egusphere-2024-2132', Paul Quinn, 06 Nov 2024
  • RC3: 'Comment on egusphere-2024-2132', Anonymous Referee #3, 18 Nov 2024
Joshua M. Wolstenholme, Christopher J. Skinner, David J. Milan, Robert E. Thomas, and Daniel R. Parsons

Data sets

Datasets associated with this paper Josh Wolstenholme, Chris Skinner, David Milan, Robert Thomas, and Daniel Parsons https://zenodo.org/doi/10.5281/zenodo.12795494

Model code and software

CAESAR-Lisflood 1.9j LD Josh Wolstenholme, Chris Skinner, David Milan, Robert Thomas, and Daniel Parsons https://zenodo.org/doi/10.5281/zenodo.12795494

Joshua M. Wolstenholme, Christopher J. Skinner, David J. Milan, Robert E. Thomas, and Daniel R. Parsons

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Short summary
Leaky wooden dams are a type of natural flood management intervention that aim to reduce flood risk downstream by temporarily holding back water during a storm event and releasing it afterwards. These structures alter the river hydrology, and therefore the geomorphology, yet often this is excluded from numerical models. Here we show that by not simulating geomorphology we are currently underestimating the efficacy of these structures to reduce the flood peak and store water.