Download Corby Weir Investigation Project

Corby Weir Investigation Project
Corby Weir Investigations and significant events
Background and History - Weir construction and Purpose
Concerns raised by fisheries interests - environmental impact on fish populations
EFP/SAP Workshops - discussions and evidence presented
Setting up of the Technical Working Group -> Corby Weir Investigation Project
Independent Consultant appointed - Peter Walker of APEM Ltd
Report on Options Appraisal
Final Consultation on Options with Fisheries Interests
Weir Construction
Built in 1996 to replace the weed and bridge affected site at Warwick Bridge, at a cost of
approx £300,000.
Corby Weir is a compound non-standard Crump weir design , not built to BS specification
as it incorporates a 1 : 8 rather than 1 : 5 downstream slope for fish counter
instrumentation purposes and to reduce water velocities over the weir to assist fish
passage.
The construction provides a static cross section and fixed bed to allow accurate monitoring
of laminar flow.
Its principle purpose being to provide
Continuous Flow measurement and Flood forecasting
Fish count data to determine migratory fish populations and influence management
decisions
Concerns raised by Fisheries interests
- Barrier to free movement of fish
- Predation of smaller fish particularly smolts above and below the weir
- Does the Fish Counter provide valuable data and how accurate is it ?
Workshop discussions and evidence
Short film and discussion points
Salmon stocks and rod catch
Fish counter validation and species apportionment
Nov 2012 what Options should we consider ?
Technical working group formed
First meeting Jan 14th - EA submissions of essential Hydrology requirements of CW
The Hydrology team stressed that CW is a critical component in providing continuous
flow data that has to be maintained for Flood forecasting and Flood warning – for
Carlisle and neighbouring districts developed on the Eden Flood Forecasting model
which is updated at CW giving reliable flows up to extreme flood events. This data
informs the County Flood response teams and emergency services.
The weir is the only fixed structure of its kind on the Eden and gives extremely accurate
data. The next upstream gauging stations being Temple Sowerby and Udford (Eamont).
The site also serves several functions for Water Resources management providing data
for the CAMS flow calculation, a low flow alarm site, a means of assessing effects of
abstraction by UU of water upstream at Cumwhinton and groundwater together with
discharges above the weir.
REDFA questioned whether less intrusive methods of flow measurement had been
considered . Also whether the position of CW so close to Carlisle gave sufficient time
warning of events. Additionally whether monitoring of severe flood events were reliable
due to downstream backing up effects.
REDFA stressed the need for a full and independent review of the Weir impacts on Fish
Passage.
Corby Weir Investigation Project commissioned by the EA
Independent Consultant brief agreed by parties
Consultant Peter Walker of APEM Ltd appointed
Site visit and second meeting Feb 14th
REDFA and YFF presented a prepared Position Statement setting out our contentions that
- the Weir presents a major obstruction to fish passage with added predation mortality
-the fish counter has not provided accurate count data or species apportionment
- consent for construction of the Weir from YFF/CC was reached with NRA on the
agreement that the fish counter would provide valuable data on the management of
Salmonid populations
In conclusion we acknowledged that flow measurement in the vicinity of this site is
essential for flood management and water resources purposes but that all options must
be considered to reduce the unintended long term impact to our Fisheries and the rivers
SAC designation.
This may be the only opportunity that we have to plan and bring about these
improvements in the foreseeable future
Peter Walker of APEM Ltd to present a report on his findings and provide
the Options Appraisal for Corby Weir at the next working group meeting.
Because of the technical complexities in assessing the Flow Management
requirements this date has been scheduled for March 26th
Final consultation and discussions with Fisheries interests
Evening meeting to be arranged 1st or 2nd week April