River Ribble and River Brun River Restoration Audit and Options Appraisal

Seb Bentley and George Heritage

2

Overview

• Initial Audit

• Hydraulic modeling

• Discussion

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

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 – 2DBackwater

Hydraulic modelling – 2DPool

Hydraulic modelling – 2DLow 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

Velocity Distance travelled

0.5 >100m

1 15m

1.5 7m

2 3m

2.5 struggle

Hydraulic modelling1 in 2yr –Velocities

Flood Risk

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

Restored Reaches

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