Effects of land use change on flood characteristics in mountainous area of Daqinghe watershed, China

Land use has changed in the Daqinghe watershed during 1956-2005, and it has influenced the flood peak and volume. In order to reveal the effects of land use change on flood characteristics in Daqinghe watershed, we selected 2 sub-watersheds and used remote-sensed land use data of 1980 and 1996 to analyze changes in land use and also selected several combinations of similar rainfall events and the corresponding flood events to show how changes in land use affect floods. The forest and urban area increased and other types decreased, and flood peaks and volumes tended to decrease under similar rainfall events. To quantify the extent of change in land use affecting floods, a hydrological model incorporating the land use was established. The model combines infiltration excess and saturation excess runoff generation mechanism in each type of land use, and the simulation results agreed well with the measured flood processes in the two selected watersheds. Several floods of different return intervals were selected to be modeled under the 1980 and 1996 land use conditions. The results show that both flood peak and volume decreased under the 1996 land use condition in comparison with the 1980 land use condition in the two watersheds. Most of the flood peaks decreased <5 %, but the volume decreased to a greater extent. This result can be helpful in modifying design flood.