Tóm tắt:

In recent years, flood in the Lam river basin occurs more often with a higher level oflosses in human’s lives, property. Preventing and reducing the damage caused by flood has been an urgent issue researched by lots oforganizations and scientists all over the world a well as in Vietnam. To find a proper solution to prevent flooding, it is necessary to analyze and research factors affecting the flood directly such as rainfall, slope, soil, land use, drainage density, etc.. It would be easier ifthese factors show up on maps with corresponding levels of risk. This paper will present the method for the building ofthe drainage density hierarchical map with the input data used as the digital elevation model and the map of river systems in the Lam river basin. The calculation results show that the river network density ofthe Lam Riveris 0.59 km/km2, which is approximately equal to 0.67km/km2 in the central rivers. Based on the drainage density hierarchical map, users can get accurate and detailed information about the river network density as well as the degree offlood hazard because of this factor in the specific basins. This will be useful for flood hazard zoning and flood warning in the study area.