Research on the influence of land use changes and erosion and flood control measures on a reduction of harmful effects of extreme rainfall-runoff events has occourred at the experimental Němčický stream basin since 2005. It has been documented by obtained results of rainfall and discharge gauging and by water sample analyses that sediment transport significantly corresponds with the cover efficiency of agricultural crops. Based on the analysis of particular comparable rainfall-runoff episodes, it can be stated that the protection (e.g. grassing, growing of narrow-row crops) of slopes adjacent to watercourses has a crucial influence on the reduction in surface water pollution with insoluble substances. In such cases the efficiency of grass cover is 90-99% compared to bare soil, while the efficiency of narrow-row crops is 50-80% in comparison with bare soil. The efficiency of narrow-row crops at the time of maximum vegetation stand is close to that of permanent grasslands.