River Ribble and River Brun River Restoration Audit and Options Appraisal Seb Bentley and George Heritage
2 Overview Initial Audit Hydraulic modeling Discussion
BACKGROUND INITIAL AUDIT HYDRAULIC MODELING RESTORATION WORKS
BACKGROUND
Background The main river Ribble is 80 miles long, Starting near Ribble Head, flowing to Preston and the Irish Sea. Known for it’s assets but people, forget (sometimes intentionally) about the less exciting areas… URES came about following significant works to improve fish passage in the Calder, including the removal of Padiham and Montford weirs, and fish passes and easements at Barrowford. After achieving this, the next priority areas had to be identified and addressed through Burnley
Background - the problems Fast Flowing Narrow Man made Limited gravels Steep Poor habitat
Background – the opportunities! options in terms of making improvements for wildlife essential part of the project was that we did not impinge on the needs of people
Background Comprehensive study of Calder and Brun Restricted to maintaining a lined channel for channel stability, flood risk
APPROACH
Approach To restore some hydromorphic function and ecological habitat to the River Calder and River Brun To adjust the present engineering configuration helping to achieve the Water Framework Directive objectives for the failing rivers Stage one – A desk and field based hydromorphological audit Stage two – Options testing and hydraulic modelling
HYDROMORPHIC AUDIT AND ASSET SURVEY
Audit and survey
RESTORATION OPTIONS
Restoration options appraisal Current channel geometry
Restoration options appraisal Pool zones
Restoration options appraisal Riffle zone
Restoration options appraisal Point bar zone
Restoration options appraisal Apical pool zone
Restoration options appraisal Low flow riffle/rapid reach
Restoration options appraisal Backwater reach
HYDRAULIC MODELLING
Hydraulic modelling – Study Reaches
Hydraulic modelling – Proposals
Hydraulic modelling – 2D Backwater
Hydraulic modelling – 2D Pool
Hydraulic modelling – 2D Low Flow Riffles
Hydraulic modelling What does this mean in terms of sediment?
Hydraulic modelling What does this mean in terms of fish? Assumption – In water velocities >0.7m-1 fish will become tired. Fish 0.25m in length VelocityDistance travelled 0.5>100m 115m 1.57m 23m 2.5struggle
Hydraulic modelling 1 in 2yr –Velocities
Flood Risk Compared pre and post restoration scenarios using 1D-2D linked modelling.
Restored Reaches
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Conclusions Difficult urban setting Needed to work with sediment dynamics and ecology Audit vital in understanding system Modelling provided confidence in restoration design Two winters suggests successful dynamic equilibrium