CHARTERED SURVEYORS

Project 3: Happisburgh - Winterton Sea Defences : Shrimp,
Fish & Sediment Monitoring.
Client: Environmate Agency. 1995 to 2004


The Norfolk coastline has suffered a series of catastrophic floods since the middle ages. Concrete seawalls were constructed after the last major breach of the sand dune defences in 1953, when thousands of ha of agricultural lands and residential areas were flooded and many lives lost.

In the late 1980's, different sea defence strategies began to emerge, including the construction of blockstone rock islands just below the low tide line. In some areas sand is pumped ashore to artificially increase the gradient of the beaches and hence assist to remove energy from incoming waves.

Environmental impacts were anticipated, including some fairly major changes in the configuration of the beaches and the inshore environment in the vicinity of the reefs. Amongst various sea defence schemes around the UK that Hydrosurveys have been involved in surveying and monitoring since the mid 1990s, the Happisburgh to Winterton sea defences extend along 14 km of the Norfolk coastline.


Operation of a Van-Veen grab for monitoring seabed material

Surveys are being undertaken annually both outside and inside the reefed area. Monitoring studies are extended to the north and south of the reefed area, to provide control data over 40 km of coastline from Cromer at the northern end, to Caister-on-Sea to the south.

Positive benefits have been found in terms of increased populations of juvenile shrimp, in the protected bays that have developed behind the reefs. Adult shrimp are highly mobile and juveniles recruited from the inter-tidal zone benefit the inshore trawl fisheries over a very large area



Rock reefs at Sea Palling

 

In addition surveying and sampling seabed material to assess localised changes, the program has monitored shrimp and ground fish populations. This particular length of coast supports an important inshore shrimp trawling and fishing industry, operating out of the ports of Boston, Kings Lynn, Yarmouth and Lowestoft. The fleets exploit stocks that exist along a relatively narrow strip of nearshore water. Brown shrimp in particular, have juvenile stages that congregate along the low-tide line, and forage out onto the beaches with each rising tide. Concerns over possible effects that the changing shoreline might have on this delicate stage in the shrimp life cycle, emphasised the need for post scheme monitoring.