Review on the Role of Forest Landscapes in Watershed Hydrologic Processes

Abstract

Forest hydrology examines the flow paths and storage of water in forests and how forest disturbance and management modify the hydrologic response. Despite, the huge amount of data and knowledge acquired over the world, the result of deforestation seems to reappear every time a new catastrophic flood or drought occurrences somewhere in the world. This paper reviews literatures on the relationship between forest cover and watershed hydrologic processes. There is strong evidence that in well-watered regions, at least, stream flow response is proportional to reduction in forest cover. Response in stream flow may be almost immediate or considerably delayed, depending on climate, soils, topography, and other factors. Most of the existing literature suggests that forest has potential to reduce annual water yield and base flow, but have limited effects on peak flow rates and flooding events. The variability of the hydrologic effects is large due to differences in watershed hydrologic processes which are controlled by climate, soils, and the stage of vegetation development. Re-forestation campaigns are not likely to cause large scale changes in water yield, base flow, and flood peaks before the hydrologic properties of degraded soils are fully improved. By degrading forests, which is essential for erosion control by stabilizing the soil with roots, erosion occurs and as a result the stream carries more sediment and water becomes worse. The presence of vegetation cover in general and forest cover in particular modifies the climatic parameters and creates a microclimate whose characteristics depend on the general climate itself and the physical characteristics defining the nature and structure of the cover.

Keywords: Forest, Hydrology, deforestation, Hydrologic impacts