29/02/2024

Portsmouth Harbour Report

Executive Summary
The harbour has always depended on the scouring effect of the strong ebb tide, itself reliant
on the presence of Blockhouse Point, which physically consists of a deep bank of sand and
shingle, topped by the Fort itself.
Some 35% of the harbour has been reclaimed since 1660, radically changing the natural
geometry and tidal flows.
Dredging for the new aircraft carriers, and the subsequent erosion of Hamilton Bank,
immediately to the South of the old Fort, is the only apparent cause of the accelerating local
seashore erosion. Evidence that the Bank is yet, or will become, stable is lacking.

Immediate threat
The greatest immediate threat is the undermining of Blockhouse Fort. Even a partial
collapse would lead to a reduced tidal scour, silting and subsequent loss of deep water access.
The issue of Hamilton Bank has to be addressed and a permanent solution sought. Failure to
consider this as the cause of an otherwise unexplained and rapid seashore erosion, or even to
measure and record the changing situation, is inexplicable. The visual evidence seems
compelling – see for example figs 33-36 [pages 31-2].
Potential sale of the establishment is inappropriate in the current circumstances.
No agency accepts responsibility and, until the cause is addressed, action is restricted to
reactive work of a strictly temporary nature. No permanent repairs are currently planned.
Cumulative Threats
As to the harbour itself, it is served by many organisations, applying their own regulations,
apparently assuming that the overall process will cover everything. Small, relatively
insignificant schemes continue to pass through the system causing cumulative damage to the
harbour. No single authority has been identified, charged with either holding these
organisations to account or safeguarding the future of the harbour as a whole.
To inform such decisions, no relevant corporate memory for the harbour has been located.

The paper concludes that urgent action is required to avert the immediate threat, and
identifies some possible future solutions, such as the introduction of a Harbour Board.
If we do not stop abusing Portsmouth Harbour we will lose it.
The historical overview of the harbour is included to give context to the present situation.
Busy readers might wish to turn directly to ‘Current Issues’, starting on page 29.

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