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Blanket‐peat restoration: numerical study of the underlying processes delivering Natural Flood Management benefits

Lookup NU author(s): Dr Salim Goudarzi, Dr David Milledge

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Restoration of eroded blanket‐peatlands through revegetation and gully‐blocking is observed to also deliver significant Natural Flood Management (NFM) benefits (reduce&delay floodpeaks). But there is a lack of clear understanding regarding how different catchment processes interact/counteract under each intervention scenario. We seek to provide more insight by rigorously calibrating TOPMODEL rainfall‐runoff model to different experimental catchments each representing an intervention scenario. Through numerical experimentation with the calibrated parameters, we estimate the impact‐magnitude of different processes. Our findings confirm the NFM benefits of these restoration‐focused interventions. In both interventions and in our largest storms, both the delay and reduced floodpeaks are primarily due to surface roughness reducing the floodwave speed thus thickening the overland flow; we conceptualise this as an increase in a ‘kinematic storage’. Impact of gully‐blocking in increasing kinematic storage is very significant and comparable to that of revegetation alone. Interventions’ impact on ‘static storage’ (interception+ponding+evapotranspiration) becomes important for smaller storms. Although interventions always increase lag times, they can be less effective in reducing peak magnitude when maximum rainfall intensity is sustained for durations longer than mean catchment delay. We propose two approaches to further increase catchment’s static and kinematic storage. Finally, while our field‐scale numerical study contributes to the evidence‐base for NFM’s effectiveness, it also provides a basis for modelling these interventions in the future. Such catchment‐scale numerical studies are necessary to (1) extend our findings to spatial scales where flooding can cause socioeconomic damage, and (2) to provide a tool for optimising the distributed configuration of these interventions.


Publication metadata

Author(s): Goudarzi S, Milledge DG, Holden J, Evans MG, Allott TEH, Shuttleworth EL, Pilkington M, Walker J

Publication type: Article

Publication status: Published

Journal: Water Resources Research

Year: 2021

Volume: 57

Issue: 4

Online publication date: 02/04/2021

Acceptance date: 27/03/2021

Date deposited: 18/06/2021

ISSN (electronic): 0043-1397

Publisher: Wiley-Blackwell Publishing, Inc.

URL: https://doi.org/10.1029/2020WR029209

DOI: 10.1029/2020WR029209


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