Malcolm Bray

Predicting coastal evolution using a sediment budget approach: a case study from southern England

Abstract Despite the fact that coastal evolution occurs over a range of temporal and spatial scales, most existing modelling tools for predicting coastal evolution are founded on the science of the small-scale coastal processes. This paper discusses the role of a variety of approaches to predicting coastal evolution and considers that the ability to predict long-term (e.g. 50–100 years plus) larger-scale changes in coastal systems is of paramount importance to coastal managers if the ultimate aim of developing long-term sustainable management of the coast and its resources is to be achievable. The advantages of a sediment budgetary approach to predicting coastal evolution are discussed and it is suggested that such an approach is better suited to predicting long-term and large-scale coastal behaviour than existing hydrodynamic and physical models. The procedure for developing a conceptual sediment budget model for predicting coastal evolution is outlined, based upon the identification of littoral cells, and consideration of sediment sources, throughputs and sinks. This modelling procedure is then applied to a “real case” coastal unit located in central southern England, namely Poole Bay, in order to exemplify its benefits and the type of results achievable. From the model, it is suggested that the most appropriate strategy for Poole Bay is one of continued beach replenishment, with maintenance of the existing seawall and groyne defences.

Extreme wave events in the central Mediterranean:geomorphic evidence of tsunami on the Maltese Islands

Field evidence from the Maltese Islands is presented of extreme wave activity in the central Mediterranean Sea. An extensive range of extreme wave signatures, both erosional and depositional, is here presented for the first time and indicates a wave attack from the NE. Existing models of runup and boulder detachment imply that the extreme wave signatures lie beyond the capabilities of storm waves. These considerations, taken together with the range of evidence available, point toward tsunami as the agency responsible, which is consistent with the evidence from Mediterranean marginal coasts opposed to the Maltese Islands. Evidence from existing boulder detachment, tsunami runup and wave velocity models suggests that tsunami with shoreline wave height of up to ∼4 m, and with local velocities of >10 ms–1 would have been required in order to form the signatures observed.

Sediment transport analysis as a component of coastal management - a UK example

Detrimental effects of engineering works on the coast and a wish to conserve parts of the coastline have increased realization among coastal managers of the need to examine shoreline problems and proposals for protection in a wider spatial context than the site itself and over a longer time scale than the past few years. This paper outlines the approach taken in one region of the United Kingdom, the central south coast of England, to provide that wider perspective. Authorities responsible for coastal protection and sea defenses formed a coastal group, which, among other activities, commissioned research aimed at providing a greater understanding on which to base shoreline management decisions. A major project undertaken was a sediment transport study in which all existing information relating to coastal sediment processes in the region was collated and analyzed. All inputs, flows, and outputs of sediment were documented. Links between processes were examined for each part of the region. Finally, nine littoral cells of sediment circulation were identified and were suggested as forming a framework for shoreline management. The methods of compilation and analysis are outlined here and are exemplified for one area in the region. The approach is recommended as a cost-effective basis for strategic management of the coast in developed regions.

Tsunami landfalls in the Maltese archipelago: reconciling the historical record with geomorphological evidence

Abstract The Maltese Islands lie in the middle of the tsunamigenic Mediterranean domain, around whose margins and islands evidence of historical tsunami landfall has been increasingly recognized in recent years. Critical review of historical evidence of events in 1693 and 1908 indicates extremely modest tsunami impacts. In marked contrast, though, recently discovered geomorphological evidence summarized herein suggests that Maltas coastlines have been overwashed up to elevations of >20 m above sea level by an exceptional event. A new perspective is provided by a review of the central Mediterranean context within which the Maltese evidence is located. Recent advances in understanding the Holocene sequence forming the floor of the Mediterranean Sea present a new stratigraphic and temporal framework within which to elucidate tsunami history. Within 100 km of Malta, terrestrial stratigraphy on Sicily also provides supporting evidence of tsunami impact. Review of these advances suggests that the exceptional event required to emplace the most extreme sedimentary and geomorphological signatures on and around Malta is likely to have had a far-field origin. The currently available circumstantial evidence points strongly towards a probability that the AD 365 earthquake and tsunami were responsible. This, in turn, enables critical reassessment of the exposure of Malta to tsunami hazard.

Intertidal boulder transport: a proposed methodology adopting Radio Frequency Identification (RFID) technology to quantify storm induced boulder mobility.: A methodology to quantify boulder transport using RFID tagging

Boulder transport is an area of growing interest to coastal scientists as a means of improving our understanding of the complex interactions between extreme wave activity and the evolution of rocky coasts. However, our knowledge of the response of intertidal boulder deposits to contemporary storm events remains limited due to a lack of quantifiable field-based evidence. We address this by presenting a methodology incorporating Radio Frequency Identification (RFID) tagging and Differential Global Positioning Navigation Satellite System (DGNSS) technology to monitor and accurately quantify the displacement of RFID tagged boulders resulting from storm wave activity. Based on preliminary findings we highlight the suitability of the technology and methodology to better understand the spatial and temporal response of intertidal boulders to contemporary storm events. We inserted RFID tags in 104 limestone boulders (intermediate axes from 0.27 to 2.85m) across a range of morphogenic settings at two sites on the intertidal shore platforms at Bembridge, Isle of Wight (UK). Fifteen topographic surveys were conducted between July 2015 and May 2017 to relocate and record tagged boulder locations (tag recovery rate: 91%). The relocated boulder coordinate data from both sites identified 164 individual transport events in 63% of the tagged boulder array amounting to 184.6m of transport, including the displacement of a boulder weighing more than 10 tonnes. Incidents of boulder quarrying and overturning during transport were also recorded, demonstrating that despite the relatively sheltered location, intertidal boulders are created and regularly transported under moderate storm conditions. This suggests that contemporary storm events have a greater propensity to mobilise boulders in the intertidal range than has previously been realised. Consequently, by documenting our methodology we provide guidance to others and promote further use of RFID technology to enable new hypotheses on boulder transport to be tested in a range of field settings and wave regimes.

Book Review: Coastal and estuarine management

The unintended and initially unpredictable side-effects or impacts of human activities at the coast form the main subject of this text. It argues that impacts upon physical qualities relate either to sediment (deficit or surplus) or pollution and generally affect habitats and coastal amenities in an adverse manner. Following a detailed and systematic discussion of these impacts resulting from activities such as coastal defence, industrial development and tourism, a concluding chapter directs attention towards appropriate management methods. In view of the focus upon impacts and the fact that many of these result from lack of management, the title of this work might be considered a little misleading even though the subject-matter is compelling. The text is aimed at an undergraduate audience and its range is global although many of the examples are based upon experiences from the UK. Its scope is similar to the earlier text by Viles and Spencer (1995), although its treatment of the subject differs. In p a r t i c u l a r, it provides a cohesive overview of the full range of impact types and their historical dimensions rather than advanced treatment of specific problems. It also provides a useful discussion of management options although much of this is based upon recent UK practice. French, P. W. 1997 London: Routledge. xvi + 256 pp., £50.00 cloth, £15.99 paper. ISBN: 0 415 13758 6 cloth, 0 415 13759 4 paper

Book Review: Coastal problems: geomorphology, ecology and society at the coast

Viles, H. and Spencer, T. 1995 London: Edward Arnold. x + 352 pp. £40.00 cloth, £15.99 paper. ISBN: 0340 62540 6 (cloth); 0340 53197 5 (paper)