Quantifying the impact of blanket-peat restoration interventions in terms their Natural Flood Management (NFM) potential
Abstract
In the UK, as in many other countries worldwide, there has been considerable recent interest both in restoration of ecosystems disrupted by human activity and in decentralised natural flood management. Since many UK rivers originate in blanket peat catchments, both NFM and peatland restoration interventions have generally resulted in similar activities, particularly re-vegetation, and gully-blocking. However, there is little evidence on the hydrological effects of these interventions on peatlands. A recent Before-After-Control-Intervention (BACI) experiment shows that these interventions can significantly reduce flood-peaks and increase lag-times, but the processes that control these effects remain unclear. We seek to identify these processes at the BACI sites by inverting the TOPMODEL rainfall-runoff model, linking the response-to-intervention in each catchment to model parameters through rigorous calibration. By analysing parameter shifts and conducting a series of numerical experiments, we infer which processes are more likely to be driving the observed changes in peak discharge and timing. We find that: 1) both treatments increase evapotranspiration rates, which can be important smaller storms; 2) the influence of additional interception storage added by revegetation of bare peat areas on peak discharge is trivial; 3) additional in-channel block storage can be important in smaller storms; 4) in large storms, changes in lag-time and peak-discharge are almost entirely the result of increased surface roughness, which reduces the flow velocity and hence increases catchment `dynamic' storage; 5) it is the in-channel `roughness property' of gully-blocks that attenuates the flow, not their storage; 6) the additional reduction in the catchment-average velocities due to gully-blocking is very significant in its impact and could have a comparable impact on peak timing to that of re-vegetation alone.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH083.0007G
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 1632 Land cover change;
- GLOBAL CHANGE;
- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1836 Hydrological cycles and budgets;
- HYDROLOGY