ABSTRACT
This introductory chapter defines urban hydrology as a scientific discipline, falling under the Earth Sciences disciplines. This relatively young scientific discipline has developed as a specialised area of hydrology as a result of the considerable increase in the number of urbanised areas on Earth, as well as the increase in the number of inhabitants living in these areas. This chapter introduces the differences between the hydrology of urbanised areas and the hydrology of natural catchments. It also defines the water cycle in urbanised areas, which includes infrastructural elements created by human activity for the needs of life in urban areas. These include water supply systems and their components, as well as water disposal systems, such as sewerage networks and wastewater treatment plants. Furthermore, this chapter examines the alterations to the natural water cycle in urbanised catchments and their consequences. These include an increase in total runoff volume, changes in runoff dynamics, and, most notably, the contamination of runoff from urbanised areas due to surface pollution resulting from anthropogenic activities. Understanding these changes, their analysis, and the definition of their causes is crucial for comprehending their consequences and for devising solutions to the problems caused by runoff, including stormwater runoff from urbanised areas.
