Analysis of the Portuguese west coast morphology and morphodynamics, based on aerial images and GIS tools

Abstract

Several areas of the western coast of Portugal are undergoing severe erosion. Accurate knowledge of coastal morphology and morphodynamic characteristics as well as their correlation through time is of great importance, not only to identify coastal erosion hazards, but also to understand more in-depth the movement of sediments and the action of currents, which are the main coastal processes responsible for erosion. The main goal of this work is to develop a tool capable of performing aerial image analysis, visual and computed, of coastal forms and wave breaking zones The results of this analysis will be integrated and made available through a GIS database. With this approach, it will be possible to typify, classify and analyse coastal physiography, and the coastline evolution, in a medium to long term period, as well as the hydromorphologies and coastal forms resulting from the wave action. The first step of this work was to store the available data into a GIS database, namely the images from the 1996 and 2001 surveys. All the surveys that dont have coordinate systems were georeferenced using AutoCAD Map 2002 and ArcInfo 7.2.1. In parallel, a tool made with Matlab 7.0 namely its toolbox image processing is being developed to analyse the stored images. Also, another tool using Geographical Information Technology (GIT) is being used to perform some more aerial image analysis. The preliminary results of this work indicate that this approach is satisfactory. The analysis system is performing well but some improvements can be introduced to the Matlab tool in order to make it able of processing imagery analysis disregarding its resolution. So far it is still unable to process high resolution images which are currently under development.