Abstract
Abstract. Open ditch drainage has historically been a common land management practice in upland blanket peats, particularly in the UK. However, peatland drainage is now generally considered to have adverse effects on the upland environment, including increased peak flows. As a result, drain blocking has become a common management strategy in the UK over recent years, although there is only anecdotal evidence to suggest that this might decrease peak flows. The change in the hydrological regime associated with the drainage of blanket peat and the subsequent blocking of drains is poorly understood, therefore a new physics-based model has been developed that allows the exploration of the associated hydrological processes. A series of simulations is used to explore the response of intact, drained and blocked drain sites at field scales. While drainage is generally found to increase peak flows, the effect of drain blocking appears to be dependent on local conditions, sometimes decreasing and sometimes increasing peak flows. Based on insights from these simulations we identify steep smooth drains as those that would experience the greatest reduction in field-scale peak flows if blocked and recommend that future targeted field studies should be focused on examining surface runoff characteristics.
Highlights
In the UK there are approximately 2.9 Mha of upland peatlands, with the majority of this present as blanket peatlands (Holden et al, 2004)
This study has used a simplified physics-based model that encompasses our understanding of important peatland drainage processes to produce evidence about and uncertainty analysis of the effects of drainage management on flood peaks
The model suggests that drainage of peatlands will increase peak flows and that drain blocking will usually decrease peak flows but may increase them in some cases
Summary
In the UK there are approximately 2.9 Mha of upland peatlands, with the majority of this present as blanket peatlands (Holden et al, 2004). Wallage et al, 2006; Worrall et al, 2007b) the impact on peak flows has not been determined conclusively This is largely due to a lack of suitable data; most experiments examining the impacts of drain blocking have focused on changes in water table levels The difference between the catotelm and acrotelm are primarily related to the fact that the catotelm is almost always saturated leading to anoxic conditions (Evans et al, 1999), changes in water table heights may alter the relative thickness of these two layers The recovery of these altered properties following drain blocking is unclear, largely due to a lack of experimental evidence to measure properties both pre and post-blocking (Wilson et al, 2010). The original and adapted models are used to explore the effects of peatland drainage management (intact, drained and blocked drains) under varying site conditions. – Identify field data that could improve the model structure and assist in the reduction of prediction uncertainty
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