Floodplain Management in Urban Developing Areas. Part I. Urban Growth Scenarios and Land-Use Controls

Some of the most critical flood problems occur in urban areas where values at risk are higher and damages tend to be heavier. Fast urban developing regions raise very specific problems because of the unsteady situation of these regions in terms of catchment land-use and urban encroachment. A realistic approach to flood management in these situations requires the consideration of urban growth scenarios and the simulation of the corresponding flood conditions. Coastal towns are frequently located in floodplains and are subject to flood hazard. This is the case for many coastal areas in Southern Europe that are still developing fast due to migration of the population to these areas. In such cases, flood management cannot be dissociated from land-use management, and non-structural measures for flood control can play a crucial role. It is important to make an ex-post evaluation of these types of measures in areas where they have been adopted. These issues are addressed in two Portuguese catchments, representative of urban growth and related to flood problems in Portugal and other Southern European regions. The Laje catchment is used for the ex-post evaluation of nonstructural measures, and the Livramento catchment is used for the modelling of urban growth scenarios. Quantitative results and policy recommendations are presented based on these two case-studies. Floodplain management is better done with GIS, especially if it is linked to hydrologic and hydraulic modelling capabilities. The use of GIS for conducting these studies is presented in Part II of this article.