A methodology for the classification of estuary restoration areas: A management tool
Abstract Planning the recovery of estuarine areas represents a major challenge for environmental managers, who must find a balance between the desired environmental restoration, understood as the return to natural conditions, and the different socioeconomic uses currently borne by the estuaries. This work presents a methodology to optimize decision-making in accordance with the objectives which might arise in projects for the hydrodynamic restoration of estuaries. Socioeconomic issues are not considered in this study. The new approach is based on a classification of the zones to be restored according to characteristics representing their hydrodynamic performance and the possible morphodynamic effects of the restoration on the rest of the estuary. To achieve this, the four following parameters were chosen: (1) changes in tidal prism induced by restoration of that zone (ΔΩ), (2) the distance between the concession and the estuary inlet (L), (3) the tidal wave phase lag (φ) and (4) the flood potential of the restoration area (I). The classification combines self-organizing maps (SOM) and the K-means algorithm. The methodology was applied in a total of 139 areas (concessions) on ten estuaries along the entire coast of Cantabria (Northern Spain) where a Spanish Ministry of the Environment Recuperation Plan is under way. The results classify the 139 areas of restoration into five clusters. Empirical relationships were used to estimate the effects the restoration of each cluster may have on the estuary's various morphodynamic elements (cross-sectional area of the estuary mouth, area of tidal flats, volume of tidal channels and volume of the ebb tidal delta), giving managers an overall view of the potential effects of the restoration in each zone and providing a basis on which to plan these actions.