Recent trends of more frequent flood events on the river Tisza (its watershed is shared by five countries of Eastern/Central Europe, and the largest part of lower reaches can be found in Hungary) highlight the research aim of our team to provide forecasts of different types of flood characteristics. International forums discussed possible causes of this increase in flood frequency and intensity. Some of the potential effects: recent very intense clear cutting of forest at headwaters (on steep slopes of the Eastern Carpathian Mountains), increased frequency of storms with intense precipitation, change in annual precipitation distribution over sub-catchments, regional effects of global warming, etc. In the present paper various techniques have been applied including time series analysis, multivariate statistics, fuzzy logic, simulated annealing, etc. Data sets of monthly and daily precipitation amount of several stations in the river basin are compared and analyzed, as well, as channel flow of the river at several cross sections for the last two-three decades. Furthermore, changes in land use/land cover, especially the forest vegetation have been taken into consideration using satellite imagery (e.g., Landsat images from 1986, and NOAA MODIS data from 2000).