වැස්ස VæSSA VæSSA Product Sheet: Historical Flood Map May 2003
Product Specification Type of product
Historical Flood Map - Event May 2003
Area covered
The Southern districts of Matara and Hambantota are covered for a big part. The district of Galle only a small part (total area: 141,158ha)
Temporal detail
3 dates: 20/05/2003, 22/05/2003 & 26/05/2003
Thematic detail
3 classes: (flood) water, reference water (dry season) & land (no water)
EO data sources used
RADARSAT1, SPOT4, Landsat7
Spatial resolution
20-30 meters (Minimum Mapping Unit: 0.54 ha)
Thematic accuracy
80-90% (see product validation sheet)
Product aim and benefit The VæSSA service “Historical Flood Map” provides valuable information to support risk- and water resource management in the context of flood prevention and climate risk mitigation. Concretely, the service is a valuable asset for the calibration and validation of (flood) risk models. Moreover, EO is also an effective method to communicate potential risks, hence to influence the dialogue with the stakeholders to convey the importance of prevention/mitigation efforts. In VaeSSA, 4 flood events are mapped.
VaeSSA is carried out under the VAE programme of, and funded by, ESA. The view expressed here can in no way be taken to reflect the official opinion of ESA
වැස්ස VæSSA VæSSA Validation Sheet: Historical Flood Map – May 2003 Ideally, the validation of the flood extent map is executed by checking the accuracy through the comparison with a VHR satellite/aerial image over the same area at the same date. Such VHR data are not available. In order to maximize the validation procedure, the accuracy of the mapped flood extents are validated through the comparison with local information (reports & press articles). The following figure shows the Maximum Flood Extent Map and some external collected information.
Validation procedure As VHR reference data is not available, no standard accuracy assessment is performed. Nonetheless, flood event information on the inundated areas are gathered (reports, press and newspaper) at the time of image acquisition. The inundated places mentioned in the articles are compared with the Historical Flood Extent maps.
Accuracy measures In the validation method “comparison with local information” the content of the different report is in line with the VaeSSA HFM’s. Nonetheless, it can be expected that the quality of this classification is lower than the other events mapped in VaeSSA. This is due to the quality of the input satellite imagery that was moderate as 2 out of the 3 images were only panchromatic imagery with considerable clouds.
VaeSSA is carried out under the VAE programme of, and funded by, ESA. The view expressed here can in no way be taken to reflect the official opinion of ESA
