Deforestation has a significant impact on the characteristics of drainage basin hydrographs, particularly by increasing peak discharge and reducing lag time.

Deforestation, defined as the removal of trees and vegetation, profoundly influences the behavior of drainage basins. A hydrograph is a graphical representation that illustrates the discharge (the volume of water flowing in a river) over a specified period. Two critical elements of a hydrograph that are notably affected by deforestation are peak discharge and lag time.

Peak Discharge is the maximum flow of water observed following a rainfall event. In deforested areas, the number of trees available to intercept rainfall diminishes, resulting in a larger volume of water reaching the ground directly. Consequently, this leads to an increase in the volume of water entering the rivers, thus elevating the peak discharge. This higher peak discharge can result in more frequent and severe flooding, as rivers may struggle to accommodate the increased water volume.

Lag Time, defined as the interval between the peak rainfall and the peak discharge, is also impacted by deforestation. In forested environments, trees and vegetation slow the movement of water, which tends to extend the lag time. However, when trees are removed, water can flow more rapidly into the river systems, thereby reducing the lag time. A shorter lag time can heighten flood risk, as it means that peak discharge occurs sooner after a rainfall event.

Additionally, deforestation affects the Base Flow of a river, which represents the normal discharge level in the absence of rainfall. Trees are vital in sustaining base flow by storing water and gradually releasing it into the soil, from where it seeps into rivers. The removal of trees eliminates this crucial water source, which can lead to lower base flows and drier river conditions.

In summary, deforestation markedly alters the dynamics of drainage basin hydrographs, increasing the risk of flooding and potentially resulting in lower river flows. This underscores the importance of sustainable forest management practices for preserving the health of our rivers and mitigating flood hazards.