Beach Erosion Vulnerability Assessment

Beach Vulnerability Index Development as Planning Measures to Counteract Erosion

Erosion is a major threat for coasts worldwide, beaches in particular, which constitute one of the most valuable coastal landforms. Vulnerability assessments related to beach erosion may contribute to planning measures to counteract erosion by identifying, quantifying and ranking vulnerability.

Herein, we present a new index, the Beach Vulnerability Index (BVI), which combines simplicity in calculations, easily obtainable data and low processing capacity. This approach provides results not only for different beaches, but also for different sectors of the same beach and enables the identification of the relative significance of the processes involved. It functions through the numerical approximation of indicators that correspond to the mechanisms related to the processes that control beach evolution, such as sediment availability, wave climate, beach morhodynamics and sea level change.

The BVI is also intended to be used as a managerial tool for beach sustainability, including resilience to climate change impact on beach erosion.

Introduction

Beaches are by nature unstable coastal landforms as they respond to changes in sediment supply, nearshore hydrodynamics and sea level. Across Europe, coastal erosion has been a longstanding, large-scale issuewith more than 40% of the beaches in France, Italy and Spain being under erosion. Similarly, in the USAof the 33,000 km of eroding shoreline, some ,300 km are beaches. Moreover, beach erosion poses a major threat not only to interconnected ecosystems, but also to stakeholders, as it is related to beach property valuesand tourism.

Beach evolution depends on processes such as sediment availability, storms causing changes that persist with time, complex interactions between nearshore and onshore sedimentary bodies, sea level riseand the broader coastal geological setting. Erosion, on the other hand, is usually the combined result of a wide range of factors, both natural (e.g. winds, storms, nearshore currents) and human-induced (e.g. coastal engineering, river basin regulation) that operate on different time and spatial scales.

Thus, quantification of these factors becomes more difficult due to their variability and coupling of the processes that affect coastal areas, and also to the frequency at which coastal changes occur. The estimation of the vulnerability of coastal areas to erosion has received considerable attention and a vast literature is available in this field; however, most of this is associated with sea level rise, induced by climate change. In the case of beaches, early attempts were based upon simple approaches, focusing on erosion due to sea level rise. More recently, methods estimating vulnerability associated with storms have been developed.

To this direction, we present an index dedicated to the assessment of vulnerability to erosion exclusively of beaches, considering the predominant hydro- and sediment- dynamic processes that contribute to beach evolution. Moreover, the new Beach Vulnerability Index (BVI) refers to beaches, regardless their size, and to the features of the associated coastal environments, incorporating processes operating over long (e.g. a gradual change in sea level) and short (i.e. storm events) time periods. Special effort has been placed upon the index estimation in order to require easily obtainable data and to avoid calculations demanding high processing capacity.

Source: Scientific Reports

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• Environment