ABSTRACT
Urban catchments are characterised by a high degree of diversity, and there is a need to identify their basic parameters describing the physical and geographical characteristics, as well as meteorological conditions (Rainfall) resulting in outflow from the catchment, or the phenomena of stormwater overflow. This chapter discusses the methods for determining catchment characteristics in terms of topographic data (land use, slope), drainage network (length, diameter of channels, ordinate of the bottom of manholes, and their height). The principles to be followed in locating rain gauges in urban catchments are discussed. Attention was focused on the selection of the appropriate number of them depending on the size of the catchment area. Basic parameters describing the dynamics of variability during rainfall events (duration, depth of rainfall, maximum 5, 10, 15-minute rainfall in an episode) were presented. The important aspect of the selection of rainfall resolution for the purpose for which they are to be used (construction of the RTC system, design of the sewerage network, including detention basins, and also for averaging the stormwater quality, evaluation of the performance of the sewerage system, etc.) was discussed. The basic models for forecasting rainfall with the appropriate frequency of occurrence and duration were discussed, which is now usually the basis for making design calculations for a sewerage network.
