Vegetation is playing an important role in the hydrologic cycle. As has been found in many Third World countries, forests are significant in flood control. They help to buffer runoff during and after strong precipitation events by intercepting rainfall. Surface runoff is reduced and seepage into the ground increased. Ground water replenishment in overused regions is also expected.

On average, forests have higher interception rates than grass lands. Additionally, a natural filtering effect reduces the amount of particulate matter in the runoff. Interception plays an important role in the hydrologic cycle, which is frequently underestimate.

Attenuation of effects resulting from high runoff rates during monsoon rains is a major goal of urban planning in tropical countries. Urban climate is highly influenced by forests in the cities and their vicinity: temperatures are lower, humidity is balanced and air pollution reduced.

Since detailed and up-to-date land cover information is often not available for hydrologic modeling the need to develop a strategy to collect these data efficiently arises. Airborne laser scanning (LiDAR) offers a fast and detailed method to detect to actual surface of large areas in 3D. Thus, buildings and infrastructure can be modeled as well as pervious areas and terrain height. The latter two are important input parameters for hydrologic modeling. The derivation of detailed tree parameters from LiDAR data can substitute laborious and time consuming field measurements as research, mainly in the field of forestry, has shown. These data are not only important for land management and urban planning, but will serve as additional input into a GIS-based hydrologic model.