ABSTRACT
A feature of urban drainage basins is the lack of homogeneity, significant variability in land use and, consequently, physical as well as geographic characteristics within them. As a result, this leads to large variations in the concentration of surface runoff, which is reflected in the variability of stormwater runoff flow rates in channels. This chapter discusses examples of rainfall-runoff models (isochron method, unit hydrograph) and nonlinear reservoirs, which are implemented in the Storm Water Management Model (SWMM). The basic factors and phenomena shaping surface runoff (infiltration, inception, evapotranspiration, field retention) are discussed. The parameters describing the variability of infiltration over time in selected models that are used in modelling urban catchments are given. The model of nonlinear reservoirs is discussed in detail, and differential equations describing the variability of the thickness of the water layer, depending on the intensity of rainfall over time and on the characteristics of the catchment (land use, slope, field retention, Manning’s roughness coefficient of impervious and pervious areas), are given. Methods are given for identifying the so-called runoff path width, depending on the layout of the channel in the plan.
