Satellite-Based Studies of the 1997 Oder Flood Event in the Southern Baltic Sea

Abstract

In summer 1997 the largest Oder River flood of this century occurred from drainage area in Poland, the Czech Republic, and Germany. The spread of floodwater, which reached the Pomeranian Bight of the Baltic Sea end of July, was monitored and investigated by satellite data, shipborne measurements, and coupled biophysical modeling to document impacted coastal waters and to assess changes in water quality and influences on the ecosystem. This paper presents the spatial and temporal floodwater distribution patterns as determined from satellite data with different spectral ranges and spatial resolutions and the relationships of these flooding patterns to meteorological conditions and river discharge rates. The flooding patterns were observed using approximately 80 sea surface temperature (SST) maps, derived from infrared data of the Advanced Very High Resolution Radiometer (AVHRR) operating on weather satellites of the National Oceanic and Atmospheric Administration (NOAA). The flood period was characterized by dominant easterly winds transporting the floodwater along the German coast into the Arkona Sea. In situ measurements and data of the visible spectral range from NOAA weather satellites and the Indian satellites IRS-P3 and IRS-1C with ocean color sensors were used to study the distribution of water constituents in the Szczecin Lagoon and Pomeranian Bight and to verify results from the SSTs. The maximum horizontal extent of discharged river water covered an area larger than 3,000 km 2 in the Pomeranian Bight and the southern Arkona Sea by 20 August. The eastern part of the Szczecin Lagoon was directly influenced by the floodwaters, leading to lower concentrations of water constituents and verifying the diluting effect. The in situ measurements in combination with the satellite observations provided an added assessment of potential impacts from floodwaters on the affected coastal ecosystem.