Does Deforestation can contribute to changes in flooding intensity and frequency?

Deforestation has caused mainly from human activities such as fires, illegal land reclamation, pasturing, etc. (Kotoulas, 1980). Deforestation promotes flooding and land degradation and reduces freshwater availability. Forest cover absorbing rainwater and reducing subsequent flooding (Brown et al. 2005). In my point of view, the restoration or creation of forested land help to decrease runoff. Numerous field studies (Robinson et al., 2003) indicate significant flood increases as a result of deforestation. This is attributed to decreased interception storage in the canopy, decreased litter storage on the ground as well as changes in soil related to infiltration capacity. Indeed, deforestation can be associated with a reduction in soil infiltration capacity. This causes more rainfall to runoff over the surface, and particularly where drains and roads enhance the accumulation and transfer of water into the stream, this can increase peak flows considerably. After forest removal if the soil can retain less of the infiltrated water, provided that the excess water rapidly finds its way to the stream. Soil water use rates tend to decrease after deforestation. The removal of trees from a large portion of a watershed, particularly if it involves increases in channelization or impervious surfaces, would increase that area's flooding tendency (Tollan, 2002).

There are numerous factors related to forest cover that have been found to inhibit the frequency and magnitude of flooding. These include a higher infiltration rate associated with forest soil, the ability of forest ground litter to absorb certain amounts of rainfall or snowmelt, and the capacity of the tree canopy to intercept precipitation, thus increasing the time it takes for water to reach the surface (Davie, 2003). It can reasonably be argued that deforestation was part of a process that led to reduced infiltration and greater sediment generation, respectively.

Ferreira and Ghimire (2012) analyzed that there is a widespread belief that forest management can prevent or reduce rainfall-induced flooding. There are three simple items in this regard: First, forests have higher levels of evapotranspiration, and the water that returns to the sky is not available to cause flooding. Second, deforestation is frequently associated with a reduction in soil infiltration capacity that results in more water runoff. In addition, retention of infiltrated water tends to decrease after deforestation. Third, forests are generally associated with lower levels of soil erosion, resulting in less soil filling up streams and rivers which would make them shallower and easier to flood.

Removal of trees is likely to exacerbate severe flooding in developing countries. Bradshaw et al. (2007) investigated country-level data from 56 developing countries on flood characteristics, forest cover, and geophysical characteristics, and concluded that deforestation amplifies reported flood frequency in developing countries.