Effects of 20 years of nourishments: Quantitative description of the North Holland coast through a coastal indicator approach

The Dutch coast has been eroding over more than a thousand years. Coastal retreat puts coastal functions (e.g. safety against flooding) under pressure. Since 1990, the Dutch policy aims at preventing further retreat of the coastline, but in the meantime taking the valuable dynamical behaviour of the coast into account. Therefore, sand nourishments have been preferred over hard structures to counteract the systematic erosion. In this study, the morphological development of the North-Holland coast since 1965 has been analyzed by looking at a number of indicators. These indicators are 1) representative of the morphological development of the Dutch coast at different temporal and spatial scale and 2) related to policy objectives. The indicators cover the entire coastal profile from dunes to deeper water. The analysis showed how the trends of the different indicators have been affected by the nourishment schemes applied over the last 20 years, by the natural forcings (i.e. yearly storminess), and by the construction of hard structures. From this dataanalysis, lessons can be learned regarding future nourishment strategies.