River Ribble and River Brun River Restoration Audit

River Ribble and River Brun River Restoration Audit and Options Appraisal Seb Bentley and George Heritage

Overview • Initial Audit • Hydraulic modeling • Discussion 2

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 Limited gravels Narrow Poor habitat Steep Man made

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

Audit and 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 – 2 D Backwater

Hydraulic modelling – 2 D Pool

Hydraulic modelling – 2 D 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. 7 m-1 fish will become tired. Fish 0. 25 m in length Velocity Distance travelled 0. 5 >100 m 1 15 m 1. 5 7 m 2 3 m 2. 5 struggle

Hydraulic modelling 1 in 2 yr –Velocities

Flood Risk Compared pre and post restoration scenarios using 1 D-2 D linked modelling.

Restored Reaches

Restored Reaches.

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