ABSTRACT. - Flood events in small mountain watersheds, called flash floods, have been documented rather frequently over the past decades. Floods of this type have also been reported from the hilly and low mountain catchments of Hungary. Prediction of flash floods is extremely challenging and requires the study of a plethora of environmental factors. Runoff models, such as the HEC-HMS, have been used to model floods on small (usually less than 200 km2) watersheds. Among many others, one very important input parameter to the HEC-HMS model is the soil moisture content. In a 1.7 km2 study watershed in SW Hungary, we have monitored the temporal and spatial changes of soil moisture with time domain reflectrometry (TDR) techniques. We conclude that soil moisture show a large spatial heterogeneity; however, the temporal behavior of soil moisture among the individual measurement points is extremely consistent.
Key words: flash flood, watershed, soil moisture, modeling, time domain reflectrometry