Development of a Pan-European River and Catchment Database

The availability of digital data on river networks, lakes and associated catchments and their characteristics is important for the analysis of environmental pressures and their impact on our water resources. Policies, such as the Water Framework Directive, the Nitrates Directive or the reformed CAP require the implementation of river and catchment databases for the development of River Basin Management Plans, for the reporting to the Commission, and for the analysis of pressures and impacts. The analysis of grid digital elevation models (DEMs) in combination with other geo-physical data allows deriving at least part of the required information over extended areas. This chapter presents a new approach making use of medium resolution DEMs (250 m grid-cell size) and information on climate, vegetation cover, terrain morphology, soils and lithology to derive river networks and catchment boundaries for the entire European continent. Existing methods for the derivation of channel networks at continental scale generally use a constant contributing drainage area threshold for the location of channel heads, independently of widely varying landscape conditions. As a consequence, resulting drainage networks do not reflect the natural variability in drainage density. To overcome this limitation, we propose the introduction of a landscape stratification, resulting in a limited number of landscape types reflecting drainage density. For each landscape type the local slope – contributing drainage area (CDA) relationship is then derived from the digital elevation data and the CDA threshold for locating a channel head is determined. In the subsequent channel extraction a dedicated CDA threshold is used for each landscape type. In order to comply with the needs of environmental monitoring, lakes and transitional waters are considered during river and catchment mapping and dedicated algorithms have been developed to overcome problems related to artificial depressions (pits) and flat terrain. The development of advanced and efficient processing algorithms based on the concepts of mathematical morphology allowed for the treatment of the whole European continent. The database has been complemented with the introduction of a hydrological feature code following the Pfafstetter system and the introduction of a name attribute for a large number of rivers and catchments. The described methodology has been implemented for the pan-European area. Results are validated comparing the derived data with independent reference data at varying scales. The resulting database is known as CCM River and Catchment Database, version 1.0. A second version, based on the SRTM DEM as well as on water classes derived from Image 2000 TM data is currently under preparation and should be released in 2006JRC.H.5-Rural, water and ecosystem resource