Silting in Bembridge Harbour is a serious problem

Bembridge is a popular place for visitors both afloat and on land. It has a rural character and an atmosphere of great charm. On a beautiful evening, with the sun setting in the west, the tinkling of the yachts’ rigging and the call of the birds on the mudflats, it is hard to imagine change. It would be wonderful to fix it all in aspic but unfortunately a number of factors – physical, historical and economic are inexorably affecting the future of this lovely harbour.

Sand is entering the harbour faster than it can be taken out on the tide. The future of boating, whether dinghy sailing, yachting or for the small fishing fleet, is at risk from silting.

Until the 1870s Bembridge Harbour, known in those days as Brading Haven, was a much larger estuary, reaching up as far as the quay in Brading, which is dated to Roman times. Bembridge village was merely a hamlet with a coastguard station at the entrance.

In historical times a number of efforts were made to drain the upper reaches of the estuary, culminating in the building of the embankment (completed c1870) and the later addition of the railway line. The embankment and the railway boosted the local economy, but it also greatly decreased the size of the harbour.

The reduced volume of harbour water changed the pattern of the tidal prism, and with much less water to run in and out of the harbour, there was less power in the tidal flow to carry sediment out of the harbour – the chief cause of the silting of the harbour.

Sediment enters the harbour from two sources. Some fine muds come down the East Yar River to settle at the west end of the harbour, but the main concern is the sand coming in through the entrance of the harbour on the flood tide. While the base of the spit running from Bembridge Point towards Bembridge Fort is considered to be stable, the upper layer is mobile. Wave action, a north-westerly longshore drift and the occasional south-easterly gale shift this upper layer of sand towards the entrance where it is transported into the harbour on the tide. The reduction in the tidal prism means that the ebb tide is not sufficiently strong to transport all the sand back out. The sand is building a large island in the centre of the harbour; it already emerges at half-tide and is increasing in size.

In a geological timeframe, estuaries are transient landscapes. The usual pattern is that unless there is major geomorphological or climatic change, estuaries eventually silt and fill in. Bembridge Harbour is no exception. The Brading Haven estuary dates from about seven thousand years ago, when the climate warmed sufficiently after the last fillip of the ice ages and water from melting glaciers raised sea level, causing the Eastern Solent to fill with water. In order to continue the current usage of the harbour, it is essential that there is a reduction in the ingress of sand at the entrance or the harbour will silt and become land.

There is a popular and active local initiative to rebuild the collapsed groyne on Bembridge Point. Plans have been drawn up and money is being raised successfully. The rebuilt groyne would assist in controlling sediment transported along the beach and into the harbour, reducing the bulk of the ingress and buying time for the current usage of the harbour.

Rebuilding this groyne is a complex project as it must be set deep into the ground in order to withstand the great forces involved. The cost of the project is estimated to be in the region of £200,000. Once rebuilt, the groyne will need regular attention with the removal of sand from the SE side. Annual maintenance dredging will remain essential. It is fortunate that the Harbour Authority was able to dredge the channels this summer despite Covid restrictions. It should be remembered that Bembridge Harbour is an SSSI and part of the Solent European Marine Sites (SEMS) mosaic of conservation sites so any dredging of the centre of the harbour, including the removal of the sand island, is at the discretion of Natural England. The new groyne will not solve the whole siltation problem, but it will help; for locals and harbour users, doing nothing is not an option and we wish the project well.