River Tywi

Large Scour Hole Exposing Gas PipelineRock Roll Mattress InstallationBrushwood and Rock Rolls In PlaceAccretion of Sediment Over Rock Roll Mattresses
Accretion of Sediment Over Rock Roll Mattresses

Salix were awarded a Design & Build contract to prevent further erosion of a section of the riverbank and reinstate a scour hole threatening a high pressure gas pipeline on the River Tywi.

The Tywi is designated a Special Area of Conservation (SAC) and SSSI and is one of Europe’s finest sea trout fisheries. Due to the sensitive nature of the site within an intertidal zone, it required a solution that would look as natural as possible whilst providing permanent long-term erosion protection.

A combination of Rock Mattresses and brushwood fill further up the bank allowed accretion of sediment to build up quickly covering the permanent bioengineering solution effectively. Rock Mattresses were placed 50% into the channel using a dive team to prevent bed scour over the gas pipe.

Below is a reference from the client:


Attached is one of the latest photos I took before demobilisation, which shows how well the rock mattresses and brushwood is accepting the silting and fill following some extremely high water over the past week.

I would also like to take this opportunity to congratulate your company in delivering a very good project under such difficult climatic conditions.

Your management support, when required, your professional and knowledgeable input, and your dedicated on-site team led by Rhodri Henry, ensured a successful outcome for the project. I enjoyed working with you immensely as part of the team ethic approach.

I hope we will have the opportunity to work together again.

Best regards,

Mike Wood, Project Supervisor, Wales & West Utilities.


Name: River Tywi Pipeline Protection
Client: Wales & West Utilities
Location: Carmarthen
Category: Rivers & Water Courses, Salt Marshes & Intertidal Rivers

Case Study

Tywi Pipeline Protection Case StudyDownload 

Cross Sections