Hydrology is the study of the processes of the water cycle such as evaporation, evapotranspiration, rainfall, runoff, infiltration and storage of water.
In engineering, a hydrological assessment is carried out to quantify the flow or volume of water in a river or stream, over land, in soils, in a pond or in a reservoir. This is used to assess the pluvial, fluvial or groundwater flood risk to a site or to evaluate the capacity of a soakaway, storage pond, reservoir or culvert.
Understanding the potential impact of flood water on a site is crucial to any developer looking to invest in a building scheme or any planner, engineer or architect acting as an adviser to such development. In addition, changes to the way rural land is used, coupled with deforestation, changes to the density of animal stock, diversification and winter crop cycles, can all influence water flow and can increase the risk of flooding.
Hydrological assessment is therefore used to help reassure or alert developers, planners and land managers to potential issues for concern.
It is difficult to accurately predict how any one development or individual land use change might affect the likelihood of flooding, but finding holistic strategies to reduce and control water flows while maintaining production and reducing soil loss, are at the heart of modern land management.