An AHP-derived method for mapping the physical vulnerability of coastal areas at regional scales

Abstract

Assessing coastal vulnerability to climate change at regional scales is now mandatory in France since the adoption of recent laws to support adaptation to climate change. However, there is presently no commonly recognised method to assess accurately how sea level rise will modify coastal processes in the coming decades. Therefore, many assessments of the physical component of coastal vulnerability are presently based on a combined use of data (e.g. digital elevation models, historical shoreline and coastal geomorphology datasets), simple models and expert opinion. In this study, we assess the applicability and usefulness of a multi-criteria decision-mapping method (the analytical hierarchy process, AHP) to map physical coastal vulnerability to erosion and flooding in a structured way. We apply the method in two regions of France: the coastal zones of Languedoc-Roussillon (north-western Mediterranean, France) and the island of La Réunion (south-western Indian Ocean), notably using the regional geological maps. As expected, the results show not only the greater vulnerability of sand spits, estuaries and low-lying areas near to coastal lagoons in both regions, but also that of a thin strip of erodible cliffs exposed to waves in La Réunion. Despite gaps in knowledge and data, the method is found to provide a flexible and transportable framework to represent and aggregate existing knowledge and to support long-term coastal zone planning through the integration of such studies into existing adaptation schemes

Sea Level Change and Coastal Climate Services: The Way Forward

“…Such classifications translate some simple principles on a map: for example, regardless of the future sea level, eroding sand spits, former wetlands, unconsolidated cliffs and low-lying areas exposed to storms are known to be the most vulnerable areas. Once these simple rules have been identified, elaborating a coastal vulnerability index becomes a classical multi-criteria decision mapping problem [119], involving heterogeneous data regarding the physical and human coastal environment and expert opinion [86,[120][121][122][123]. This approach considers rough SLR assumptions only (e.g., 1 m by 2100) and can identify critical areas where avoiding further urbanisation and development or planned retreat should be considered.…”

Modelling of cave-in occurrence using AHP and GIS

“…It has been used in such disciplines as, for example: geology, mining, management, economics, and environmental protection (Erden and Karaman, 2012;Le Cozannet at al., 2013;Saaty, 1980). This method is based on the assumption that a complex problem can be stripped down to elements which are then weighed and integrated with problem solving as the objective.…”

Coastal Erosion Studies—A Review

“…The Analytical Hierarchy Process [5] (Saaty, 1980) is a multi criteria decision method that solves decision making problems by ranking alternatives according to several criteria. The main steps in the method involve -• Representing a decision making problem by organizing its criteria into a hierarchical structure.…”