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1 Przegląd Geofizyczny

1 2001

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Symulacja zasięgu zalewu powodziowego doliny rzecznej

Soczyńska U., Kobyłecki P., Magnuszewski A., Nowicka B., Jełowicki J.

Przegląd Geofizyczny

2001

Z. 3

183-195

Flood studies and forecasts are concentrated on a peak flow Q(max) and flood hydrograph Q(t) calculations. In this study a hydraulic flood routing model has been integrated with geographic information system containing digital elevation model of the valley floor. This allows to display the mo-deling results of both deterministic Q(x, y, t), and probabilistic Q(x, y, p), approach. Model has been tested on a data from Skora river (A=273 km2) located on a footslope of the Sudety Mountain in southwest part of Poland. A detailed study has been performed on a 15.2 km long river reach between gauges Zagrodno (A=162 km2) and Chojnow (A=270 km2). Leveling survey of the 50 floodplain cross-sections has been performed in the summer of 1999. This data has been used for proper description of the river channel geometry and weight average Manning roughness coefficients on a floodplain. For a river channel flood routing a numerical model based on the balance Saint-Venant equation has been applied (program name is SiReN). The boundary conditions in the numerical solution were flood hydrograph Q(t) at the inlet gauge Zagrodno, and stage graph H(t), rating curve Q(H) at the outlet gauge Chojnow. A numerical implicit Preissman scheme of finite differences method has been used for solving equations. At the flood passage a lateral runoff from a side catchments has al-so been considered. Manning roughness coefficients have been in addition optimized using the calculated versus observed flood hydrographs. Digital elevation model has been calculated using the digitized contour data from topographic maps in a scale 1:10 000 and surveying data from river channel cross-sections leveling. A regular grid of 10m x 10m resolution with elevation points has been obtained by the inverse distance interpolation method available in Surfer program. Matrix of elevation points has been converted to a raster image in which pixel number corresponds to a grid node value. Integration of the DEM model with other thematic maps showing landuse of the river valley floor and water surface in the channel has been done in ILWIS program. Visualization of the flood range has been done for the peak flows of 10, 1 and 0.1% probability.