CH2M helps restore UK salt marsh to enhance flood defenses, recreate estuary habitat

Denver — A new project in Hesketh Out Marsh near Preston, UK, helps protect property and nearby infrastructure from flooding while creating an internationally important estuary for wildlife. The Hesketh Out Marsh East Managed Realignment Scheme, which opened late August 2017, reinstates 160-hectares of land to saltmarsh, and by doing so, provides important climate change adaptation to counter flood risk from sea level rise.

Salt marshes are coastal wetlands rich in marine life, protecting against coastal erosion and water quality problems, and which reduce flooding while acting as nurseries and refuges for many species.

“The primary goal of the realignment project was to protect existing property and nearby infrastructure against flooding, in addition to recreating salt marsh habitats,” said Greg McIntyre, president of CH2M’s State and Local Governments sector. “We are pleased to have helped the Environment Agency and the Royal Society for the Protection of Birds to improve coastal defenses and restore this marsh, providing space for natural habitats to flourish.”

CH2M provided modelling and detailed engineering design to create appropriate habitats for wildlife. The team used numerical modeling to predict the design’s behavior over time, evaluating the impacts and enabling the area to flood and drain correctly.

The original salt marsh had been reclaimed from the River Ribble estuary with an outer wall in 1980 and used for growing crops and pasture.

With sea levels rising, the Royal Society for the Protection of Birds and the Environment Agency sought more natural ways of dealing with coastal flooding through “managed realignment”. Through work to develop creeks and lagoons and by allowing seawater back onto the land, salt marshes were created, helping absorb the force of storms before impacting the coastal defenses.

The scheme, one of the largest of recent UK managed realignment projects, helps naturalize this internationally important estuary, while protecting more than 140 properties, farmland and infrastructure against flooding.

The Hesketh Out Marsh East scheme is located next to the award-winning CH2M designed Hesketh Out Marsh West scheme, which opened in 2008. Together, the two schemes create more than 320 hectares of intertidal habitat, which will be the largest bio-reserve of its kind in the North of England.