Influence of low-impact development in flood control for a design rainfall event

Urbanisation modifies the natural hydrological cycle and aggravates floods. If the limits imposed by the natural environment are respected in the urban planning process, it is expected that the city resulting from this process will be able to coexist with floods, suffering minor damages. In this context, this work uses the concept of low-impact development (LID) to ‘go back in time’, with the aid of mathematical modelling tools, identifying an earlier moment of initial development of the city of Mesquita, in Brazil, to evaluate the flooding situation at that time and compare it with the current situation, seeking to understand how the worsening process of the urban floods evolved. Then, an alternative growth pattern is modelled from the past to the present, revising urban development guidelines to incorporate flood concerns and LID concepts. The main findings indicate that flood flows need space; the bottom of the valleys and the riverine areas should be preserved as open spaces to accommodate floods, and LID can help in preventing floods, but the excess of imperviousness is critical and very difficult to reverse.