IHBC Yearbook 2017

R E V I E W 27 and the stone reused to build the present North Quay – again, a rubblefilled masonry structure – and the entrance was improved by rebuilding the end of the South Quay with a slight overlap and an outward kick to shelter vessels in the narrow entrance. Later 19th-century structures became increasingly impermeable, designed to block an oncoming wave, forcing energy upwards and outwards. Mullion’s West Pier, built only 20 years later, has outer skins of tooled masonry with mortared joints, a concrete ‘bagwork’ hearting of ordinary Portland cement and a fulllength projecting moulding intended to deflect waves seawards (a precursor to the modern recurve). The increasing use of concrete towards the end of the century meant that seaworks entered a new phase and scale. Mousehole’s evolution highlights the importance of understanding not only fabric and structure, but also changes in harbour plan form. Despite rebuilding in 1732, Newlyn’s Old Harbour retains its original modest footprint, evidencing the limited shelter these structures originally provided. Perhaps the apogee of Cornish harbour construction is Porthleven, where almost every technique known to the 19th-century engineer was employed to overcome its exposure to the prevailing southwesterlies and waves which shoal rapidly inshore. In 1810 work began to remove the natural sandbar and the foundations for a protective pier were laid. This work was repeatedly washed away, so work began from the seaward end landwards which was successful. This structure is angled so that breakers roll along its seaward face and expend themselves upon the reef and occasionally over the Bickford-Smith Institute (1884). Even in locally calm conditions, waves generated by distant storms can diffract around the end of the pier and surge along the east outer harbour wall. The first attempt at harbour construction was a narrow rectangular basin with a wide entrance, admitting incoming breakers. Its internal symmetry resulted in reflecting waves which combined to create turbulent conditions. It was a complete failure. In the 19th-century engineers were aware that small enclosed harbours were the most difficult to design, having less space in which to dissipate wave energy. As Thomas Stevenson remarks, ‘the breaking of a free wave is a very different thing from the breaking of a wave confined by a barrier of masonry. While the first may be compared to the harmless ignition of a loose heap of gunpowder, the other resembles the dangerous explosion produced by the discharge of a cannon’ (The Design and Construction of Harbours, 1874). Substantial rebuilding at Porthleven in 1855 introduced a new breakwater. This formed a locked inner harbour, with a sluice which could be opened after high tide to release impounded water. The new breakwater and existing outer wall now formed a protective outer harbour and a high parapet was added to reduce overtopping into the inner harbour. However, the most significant challenge in this confined site was the introduction of reductive measures to dissipate wave energy sufficiently for the outer harbour to be usable. The seaward face of the new breakwater was sloped at a shallow angle and finished in rough-dressed vertical stonework to absorb rather than reflect wave energy. Its angular re-entrant corners were curved and chamfered to reduce breaking caused by colliding waves and the existing outer west wall was modified to accommodate a shallow stone apron. This is open to the harbour road and acts as a ‘spending beach’ where waves can break harmlessly. This magnificent structure survives relatively unaltered, occupied by a handful of small boats. While there remains a statutory duty to maintain Porthleven as a harbour of refuge, it has been privately owned since 1978 by a company whose core activities do not include harbour management. The UK is unique in Europe in requiring its port sector to be selffinancing. Harbours can be owned by local authorities, private individuals and companies, by associations and by harbour trusts – statutory nonprofit making bodies formed of independent harbour commissioners. As the Crown Estate claims ownership of the seabed from low water to the 12-mile territorial limit and owns approximately half the foreshore of the UK, almost all harbour authorities must lease Crown property within their jurisdiction at a market rent paid to the Treasury. All UK statutory harbours are subject to the same complex regulatory burden, including compliance with the Port Marine Safety Code which imposes a duty to maintain an open port and conserve it for use as a safe harbour. Even where a harbour is closed, proportionate compliance with the code is recommended to ensure health and safety of potential users. In 1873, Mousehole Harbour Commission purchased the Duchy Medieval boulderwork in the Grade II* listed South Quay, Mousehole (Photo: Colin Higgs, www.portreathstudio.com)

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