Upper Gade assessment and restoration options

Di Hammond  (the River Restoration Centre - rrc@therrc.co.uk)

Judy England  (Environment Agency)

Proceedings paper from the 10th Annual River Restoration Centre Network Conference, 1st - 2nd April 2009

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Abstract

The Environment Agency’s Restoring Sustainable Abstraction Programme (RSAP) had identified the River Gade, a Chilterns chalk stream, as suffering from over-abstraction. Options appraisal for river restoration was carried out to identify appropriate works, which would improve the functioning of the river at times of low flows and ensure sustainable management of the river.

Surveys used to develop the different options included GeoRHS surveys (River Habitat Surveys with an enhanced geomorphological component), detailed topographic surveys of the river, comparison of natural and gauged flows, hydraulic modelling of the discharge pipe and diversion weir. For the options appraisal cost-benefits analysis was carried out and a qualitative assessment made of the options in terms of ecological and habitat benefits.

The overall recommendation was for the removal of a number of weirs and the re-profiling of the river through Gadebridge Park, but with the proviso that flow restoration should also be carried out. In addition habitat improvements were recommended resulting from the GeoRHS surveys. The results of the study are discussed in context of the local ecology and the potential for recovery.

Keywords

cost-benefit analysis; low flows; over-abstraction