Managed realignment in the Humber estuary: factors influencing sedimentation
Thesis or dissertation
- © 2009 Jennifer Clapp. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
In September 2003 a managed realignment site was breached on the north bank of the Humber estuary at Paull Holme Strays (PHS). The site was breached as part of the Environment Agency Humber Flood Risk Management Strategy, with the main aims to create intertidal habitat to replace that which has been lost in other areas of the estuary and to alleviate increasing flood-risk associated with climate change induced sea level rise. Managed realignment is a relatively new method of flood defence that has gained in popularity with flood managers over the last 20 years. At PHS, the accretion rates predicted by modelling of the site prior to breaching were an order of magnitude slower than those recorded immediately post-breach.
This thesis outlines the monitoring programme followed that investigates the reasons for the fast accretion rates at PHS, researches the sediment properties, calculates a sediment budget and produces a conceptual model for fast accreting managed realignment sites. Results have shown that the initial fast accretion rates continued on the site to the end of the monitoring period five years post-breach, particularly on the NW sector of the site. Net sediment deposition within the site compared favourably with the amount of sediment measured as accreting on the site. A number of sediment properties that were measured did not correlate significantly with accretion rates. The main factors influencing the fast accretion were the elevation of the site and thus the tidal inundation time, and the design of the site. A flume based study of the erosion of sediment cores taken from the site highlighted differences between the SE and NW sector of PHS, again related to elevation and tidal inundation, but not between sites with differing sediment properties. The conceptual model indicates that these types of fast-accreting managed realignment sites will quickly progress to becoming mainly saltmarsh habitat within ten years, aiding flood managers in the design and monitoring of similar sites.
- Department of Geography, The University of Hull
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