ABSTRACT
Beaches that are geologically controlled by rock and coral formations are the rule, not the exception. This paper reviews the current understanding of geologically controlled beaches, bringing together a range of terminologies (including embayed beaches, shore platform beaches, relict beaches, and perched beaches, among others) and processes, with the aim of exploring the multiple ways in which geology influences beach morphology and morphodynamics. We show how in addition to sediment supply, the basement geology influences where beaches will form by providing accommodation, and in the cross-shore, aspects of rock platform morphology such as elevation and slope are also important. Geologically controlled beaches can have significant variations in sediment coverage with seasons and storms, and geological controls have fundamental influences on their contemporary morphodynamics. This includes wave shadowing by headlands and rock/coral formations inducing strong alongshore gradients in wave energy, resulting in corresponding variations in morphodynamic beach state and storm response. Geologically-induced rip currents including shadow rips, deflection rips and mega-rips that can develop on embayed beaches during storms, are an integral feature of the nearshore circulation and morphodynamics of geologically controlled beaches. We bring these processes together by presenting a conceptual model of alongshore and cross-shore levels of geological control. In the longshore dimension, this ranges from beaches that are slightly embayed, through to highly embayed beaches where headlands dominate the entire beach morphodynamic response. In the cross-shore dimension, this ranges from beaches without discernible geological controls, through to relict beaches above the influence of the contemporary littoral zone. Given the prevalence of geologically controlled beaches along the world's coasts, it is paramount for coastal management to consider how these beaches differ from unconstrained beaches and avoid applying inappropriate models and tools, especially with our uncertain future climate.
ABSTRACT
Coastal flooding caused by extreme sea levels can produce devastating and wide-ranging consequences. The 'SurgeWatch' v1.0 database systematically documents and assesses the consequences of historical coastal flood events around the UK. The original database was inevitably biased due to the inconsistent spatial and temporal coverage of sea-level observations utilised. Therefore, we present an improved version integrating a variety of 'soft' data such as journal papers, newspapers, weather reports, and social media. SurgeWatch2.0 identifies 329 coastal flooding events from 1915 to 2016, a more than fivefold increase compared to the 59 events in v1.0. Moreover, each flood event is now ranked using a multi-level categorisation based on inundation, transport disruption, costs, and fatalities: from 1 (Nuisance) to 6 (Disaster). For the 53 most severe events ranked Category 3 and above, an accompanying event description based upon the Source-Pathway-Receptor-Consequence framework was produced. Thus, SurgeWatch v2.0 provides the most comprehensive and coherent historical record of UK coastal flooding. It is designed to be a resource for research, planning, management and education.
ABSTRACT
Coastal flooding caused by extreme sea levels can be devastating, with long-lasting and diverse consequences. Historically, the UK has suffered major flooding events, and at present 2.5 million properties and £150 billion of assets are potentially exposed to coastal flooding. However, no formal system is in place to catalogue which storms and high sea level events progress to coastal flooding. Furthermore, information on the extent of flooding and associated damages is not systematically documented nationwide. Here we present a database and online tool called 'SurgeWatch', which provides a systematic UK-wide record of high sea level and coastal flood events over the last 100 years (1915-2014). Using records from the National Tide Gauge Network, with a dataset of exceedance probabilities and meteorological fields, SurgeWatch captures information of 96 storms during this period, the highest sea levels they produced, and the occurrence and severity of coastal flooding. The data are presented to be easily assessable and understandable to a range of users including, scientists, coastal engineers, managers and planners and concerned citizens.
