DETERMINING THE CHARACTERISTICS OF DIRECT RUNOFF FROM REAL RAIN USING GIS ENVIRONMENT / STANOVENIE CHARAKTERISTÍK PRIAMEHO ODTOKU Z REÁLNEHO DAŽĎA S VYUŽITÍM PROSTREDIA GIS

The selected SCS-CN method is used worldwide and adapted to the conditions of Slovakia. GIS environment provides an opportunity to simulate changes in land use, and then to calculate the total volume of water from the river and peak water flow in the river bed of the stream. The simulation was done for two rainfall events, 72 mm and 42.6 mm, which were measured in precipitation station in Jelenec (a village situated next to the area of interest). The calculation was made for 4 possible scenarios - current land use, forest, arable land and grassland and pasture. Culmination discharge and time of outflow from rainfall 72 mm for current land use were calculated using the NRCS method. The calculation of water runoff volume showed that similar values were measured for the rainfall of 72 mm and rainfall 42.6 mm in case of AMC-III. The highest values of water runoff volume were marked in the case of arable land in all calculations, the lowest one for forest. Comparison of designed stream cross section and calculated culmination discharge allowed us to determine the point of outflow from the river bed of the Drevenica stream.