Sven Vanderhaegen

A System-based Paradigm of Drought Analysis for Operational Management

Conventionally droughts are studied in terms of their dimensions (severity, duration and areal extent), without specifying the affected system. The paper presents an innovative system-based approach for drought analysis, which can lead to rational decisions for combating drought. Concepts of water scarcity (drought, water shortage, aridity and desertification) are viewed within the perspective of this new approach. The paper focuses also on operational water management in the presence of drought. Starting from the needs for such management, the affected system is defined and the related quantities are identified. Also, sub-systems are considered which allow the establishment of the link between specific variables and drought. Some drought characterisation methods are particularly suited for the systemic approach. Finally drought is considered as a natural hazard phenomenon and its consequences are discussed. Each physical sub-system can be improved by a variety of measures aiming at decreasing its vulnerability towards drought, so that the drought risk is mitigated. It is concluded that the clear definition of the affected system on the spatial and temporal scales can significantly contribute to the rational management for combating drought.

Modelling soil sealing density in residential areas for flanders and the brussels capital region

This paper presents a modelling approach for estimating the density of sealed surface cover within residential areas, using a set of explanatory variables describing the spatial context of each area, its morphological properties and its population density. The model is calibrated and applied on Flanders and the Brussels Capital Region using a 30m sealed surface cover fraction map for 2013, obtained through spectral unmixing of four Landsat 8-OLI scenes covering the study area. The work demonstrates that sealed surface cover distribution in residential areas can be explained by the density of different land uses in an areas surroundings, the distance to transport features (roads, road crossings, railway stations) and the positioning with respect to urban clusters of different size, in combination with spatial metrics describing the structure of the built-up area or, alternatively, the areas population density. Models of this kind might be used in combination with land use and population forecasts to obtain more reliable estimates of sealed surface cover density for future time steps.

Use of Earth observation for monitoring soil sealing trends in Flanders and Brussels between 1976 and 2013

The on-going growth of urban area in Flanders and in the Brussels Capital Region over the past decades has resulted in a highly sprawled urban tissue, consisting of large and smaller urban agglomerations, connected by a well-developed transportation network. The conversion of open land to urban area is accompanied by an increase in soil sealing, affecting the hydrological cycle and the urban climate. Despite a growing interest in monitoring the process of soil sealing in urban areas, to date no detailed information on the presence and evolution of sealed surfaces is available for Flanders. In this paper a linear regression unmixing approach is proposed to map and monitor changes of sealed surface cover at the regional scale, using medium as well as high resolution remote sensing data. Applied to Flanders and the Brussels Capital Region, a total sealed area of 2687 km² for 2013 is found, corresponding to an increase of 82% since 1976. Residential areas account for nearly half of the sealed area and show the largest increase in sealed surface cover over the past 37 years.