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The authors are solely responsible for the content of this report. Material included herein does not represent the opinion of the European Community, and the European Community is not responsible for any use that might be made of it.
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At the 15ha Chowder Ness site, new flood defences were created at the rear of the site to a minimum height of 6.7m above Ordnance Datum Newlyn (ODN). Material for these defences was obtained from within the site from a combination of reprofiling and the creation of temporary borrow pits.
The existing seawall was removed over a length of 570m (some 200m remain), to a level of around 1.6 to 2mODN. This removal, rather than the creation of solitary breaches, was chosen for a number of reasons:
(1) Removing the rear of the embankment;
(2) Removing the concrete wave return, the bitumen and rock face; and
(3) Overall lowering of the embankment (to levels around 1.6 to 2mODN).
As Chowder Ness was considered relatively small-scale in relation to the estuary as a whole any predicted changes to the hydrodynamics and sediment dynamics were expected be extremely localised and relatively small in magnitude (ABPmer, 2004).
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Chowder Ness
Table of content
- 1. Measure description
- 1a. Description of the issue and measure
- 1b. Status of the measure
- 1c. Monitoring
- 1d. Monitoring results
- 2. Execution of main effectiveness criteria
- 2a. Effectiveness according to development targets of measure
- 2b. Impact on ecosystem services
- 2c. Degree of synergistic effects and conflicts according to uses
- 3. Additional evaluation criteria in view of EU environmental law
- 3a. Degree of synergistic effects and conflicts according to WFD aims
- 3b. Degree of synergistic effects according to Natura 2000 aims
- 4. Crux of the matter
Description of the issue and measure
Chowder Ness was undertaken for the same purpose as another realignment on the Humber, Welwick, which is presented in a separate First Analysis Step (FAS) Report. Both schemes were designed and implemented by the same organisations (Associated British Ports (ABP) and ABPmer), and to very similar timescales and principles. To inform the final design of these sites, numerical modelling was undertaken based on LiDAR elevation data. This was to ensure the correct balance of habitats would be achieved. As mudflat creation was the main objective of the schemes, and as the sites were largely too high for this to occur, the land was re-profiled to increase the extent of lower areas where mudflat could develop (i.e. below Mean High Water Neap (MHWN)). These works included the creation of a gentle slope from the fronting, existing, mudflats to the rear of the sites to assist drainage.At the 15ha Chowder Ness site, new flood defences were created at the rear of the site to a minimum height of 6.7m above Ordnance Datum Newlyn (ODN). Material for these defences was obtained from within the site from a combination of reprofiling and the creation of temporary borrow pits.
The existing seawall was removed over a length of 570m (some 200m remain), to a level of around 1.6 to 2mODN. This removal, rather than the creation of solitary breaches, was chosen for a number of reasons:
- It improves connectivity with the wider estuary;
- It more closely recreates the type of environments that existed prior to the land claim;
- It enables the whole cross sectional area of the estuary including the realignment site, to respond to estuary wide changes; and
- It increases energy levels within the site, thereby improving the likelihood that mudflat habitat will be maintained (as mudflat creation was the main objective of the site).
(1) Removing the rear of the embankment;
(2) Removing the concrete wave return, the bitumen and rock face; and
(3) Overall lowering of the embankment (to levels around 1.6 to 2mODN).
As Chowder Ness was considered relatively small-scale in relation to the estuary as a whole any predicted changes to the hydrodynamics and sediment dynamics were expected be extremely localised and relatively small in magnitude (ABPmer, 2004).