12. The methodology for the establishment of drainage density map to serve for flood zoning in the Lam river basin

Abstract

In recrent years, flood in Cenfral region in general and Lam river basin in particular have occurred more often with severe damage to human s lives, properties and ecological environment. Preventing and reducing the damage caused by flooding have been an urgent issue studied by many organization and scientists all over the world as well as in Vieừiam. To be able to propose effective measures for flooding prevention, it is necessary to identify and analyse factors directly affecting flood such as slope, rain fall, land cover, soil and drainage density. It would be practical and effective if the indexes related to these factors shown up on maps with corresponding levels of risk. This paper presents the process for preparation of drainage density map using the the digital elevation model and the map of river and stream systems in Lam river basin as input data. These maps will be useful and valuable for hazard zoning and flood warning in the study area.