Alderbrook Stream Improvements, Cranleigh

23 05 2018

The Alderbrook Stream watercourse is in the Borough of Waverley, Surrey.  Part of the local surface water drainage network, the watercourse suffers from problems of erosion and scour caused by surges of storm water run-off.  This has led to undermining and instability of the embankments and serious erosion of the stream bed over its length.

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Left untreated these problems would lead to land slips, an increased risk of flooding and significant restoration costs.

These are typical land drainage problems facing most local authorities around the country.  Constrained by limited resources the local authority often has to coordinate and agree its own land drainage maintenance responsibilities with those of the other riparian owners.

In this case, the section of Alderbrook Stream is within Waverley’s common land ownership, making Waverley Borough Council the sole riparian owner.

 

 

The Stilwell Partnership submitted a successful tender and were appointed to carry out a feasibility study over the stream’s length that would identify and recommend targeted maintenance improvements to address these problems.

Due to its predominantly gravel-rich bedrock, the watercourse also has a diverse ecosystem, and is home to numerous spawning fish species including the wild brown trout.

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The civil engineering design solutions would have to complement the local ecology with minimal disturbance during the construction works.

We developed a number of low cost repair solutions for the watercourse and presented them to Waverley Borough Council.  We proposed gabion mattresses to replace the scoured areas of the stream bed and bag-work to support and retain the eroded embankments.

The measures were approved, and we were instructed to proceed with the  implementation. We subsequently produced detailed construction drawings, appointed a suitable contractor, and supervised the works.

The Stilwell Partnership were pleased to be involved in this successful project.

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The scheme demonstrates how low cost civil engineering measures, sympathetic to the local ecology, can be implemented to resolve typical but urgent land drainage issues, and reduce the risk of flooding.

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