Broadland Flood Alleviation Project

Covering 30,000 hectares (ha) (74,141 acres (ac)) of environmentally and economically sensitive land in the east of England, this program has provided sustainable and affordable, long-term flood defenses for rural communities – ensuring the protection and improvement of habitat for rare and endangered species and protection for some of the most productive farmland in the U.K.

The £110 million ($150 million), outturn cost in 2021 £140M ($190M), contract was awarded as a Public Private Partnership (PPP) scheme by the Environment Agency in February 2001 to Jacobs as consultant and BAM Nuttall as contractor, working together in a joint venture as Broadland Environmental Services Ltd (BESL). The program’s main purpose was to provide a strategic approach to improving the Broadland flood defenses while engaging key stakeholders and the local community.

The program area is located wholly within the Norfolk Broads river system, an extensive area of wetland with a status equivalent to that of a National Park. Program focus is to improve and maintain the flood defenses along the tidal reaches of the Rivers Yare, Bure, Waveney and their tributaries in Norfolk and North Suffolk. As well as the 28 Sites of Special Scientific Interest (SSSI), the flood defenses protect 24,000ha (59,305ac) of agricultural land, 1,700 private properties, five previously undefended communities, rail and road infrastructure systems, important archaeological and built heritage structural remains, and several recreational facilities.

Construction of major improvement work was completed in 2017, with maintenance continuing to May 2021. The program has come to its 20^th and final year of implementation, having achieved its objectives of protecting homes and farmland from flooding, while also protecting and improving habitat for rare and endangered species. Over 28 kilometers (km) (17 miles (mi)) of hard erosion protection mainly steel sheet piling has been replaced by wide reed beds through realigning (setting back) the flood bank to create more sustainable assets. This achieved a key project objective. These setback areas provide over 500,000 cubic meters for dredging disposal for the Broads Authority. Over 3 km (nearly 2 mi) of overhead electric cables are now underground, improving landscape and making the area safer for farmers and anglers. There are enhanced mooring facilities, improved navigation of channels and new slipways for boaters; new platforms for anglers, and 100 km (62 mi) of upgraded footpaths for everyone to enjoy the area.

The success of the Broadland Flood Alleviation Project demonstrates that large-scale improvement schemes that have a strategic approach to improving existing flood defenses can be accomplished within a nationally and internationally important wetland area. Long-term collaborative schemes that involve key stakeholder groups and landowners in detailed phases of public consultation can enable the development of partnership projects. These schemes achieve the desired objectives for biodiversity while reducing disturbance to important and notable sites.

The program has undertaken a substantial number of initiatives to ensure energy efficiency, enhance biodiversity, reduce emissions and minimize overall environmental impact.

The design philosophy has sought to minimize the environmental impact of strengthening the flood banks, through sourcing and using material extensively from the adjacent new soke dyke. This ensured less than 5% of the total material used on the scheme was imported. The design and construction of the new soke dykes maximized biodiversity.

The project team soon realized the opportunities for materials reuse. A pile handling yard was set up for the treatment of all removed piles. All recyclable materials, such as steel and timber piles, were cleaned and trimmed before being stock piled for re-use. The processing of these piles employed biosecurity measures to prevent the spread of killer shrimps, an invasive species presenting a serious threat to local marine biodiversity. Designs were then tailored to maximize the use of these materials – shortened piles were used as anchor piles, and timber was either used in erosion protection systems or, more innovatively, by a local craftsman to create bespoke furniture. In this way we achieved near zero waste.

The program area lies within the most important and sensitive wetland complexes in Britain. Consequently, consideration of how the natural environment should be protected and enhanced is a key aspect of scheme development.

Examples of how the natural environment has been protected and enhanced include:

• Constructing one of the largest reptile banks and hibernacula in order to provide a receptor site for hundreds of adders and lizards whilst construction work was undertaken.
• Innovative mitigation techniques, endorsed by Natural England, developed for water voles, including two academic papers on water vole mitigation.
• Seeds from rare plants were collected and new plants grown so that they could be re-introduced on completion of the construction works.
• New soke dykes incorporated berms (ledges) that provided a substrate for reed, sedges and other plants to colonize.
• The construction of new setback banks and subsequent removal of the old bank and redundant piling created new open water lagoon and reedbed habitats that are used by a wide variety of species, including marsh harriers.
• Bird and bat boxes plus artificial otter holts were constructed using timber and brash from pre-work vegetation clearance.
• The flood banks provide protection to large areas of agricultural marshland, which itself has significant biodiversity value for breeding and wintering birds, aquatic plants and invertebrates.

One of the major benefits of the long-term nature of the program is the external and partner organizations’ confidence in BESL’s program of ongoing work enabling them to make strategic decisions wholly aligned with the program. The Broads Authority based a significant portion of both its mooring and sediment (dredging) disposal strategy around BESL’s delivery plans, saving the organization money and benefitting all river users in the area.

Facilitating local community enhancements was central to the program. Flood defense work was welcomed by most and seeing this long-term investment in the area had a real benefit for local people and communities. The long-term security promoted private investment and, where possible, the team encouraged and assisted in delivering several enhancements which improved local amenities, recreation opportunities and health and well-being initiatives. BESL’s work with EDF Energy, for example, resulted in over 2 km of overhead electric cables being placed underground, reducing bird strikes, angling risks, enhancing the visual landscape and improving safety, not only for the construction team, but also local farmers.