ABSTRACT
Flood hydrology is concerned with the quantitative relationship between rainfall and the resulting outflow in both natural river channels and artificial drainage systems, and, in particular, with the magnitude and time variations of outflow. This is because all water resource schemes require such estimates to be made before design of the relevant structures may proceed. Examples include reservoir design and flood risk management, including flood alleviation schemes and land drainage. The purpose of this chapter is to introduce the reader to the estimation of design floods for rural and urban catchments. Firstly, the dominant components of the hydrological cycle that influence the generation of floods in rivers are described. This is followed by detailing the techniques and equations used in the estimation of flood frequency and the application of the generalised logistic distribution to an annual series of river flood discharges. Next, the types of computational rainfall–streamflow models used for river flood simulation are discussed, and the concept and application of the unit hydrograph (UH) technique is detailed. This is followed by developing the technique of level-pool routing for the safe design of reservoirs and the extension to river channel routing. The key aspects of urban storm drainage modelling are then described. Finally, climate change impacts and the assessment of uncertainty in flood hydrology are introduced. This chapter also provides some of the background knowledge required for the study of river engineering, which is presented in Chapter 15. Worked examples and problems for solution are also given in the text.
