Author(s)

M.G. MIGUEZ, J.M. BAHIENSE, O.M. REZENDE & A.P. VERÓL

Abstract

City growth must be carefully planned, in order to deal with the relevant hydrological changes, caused by urbanisation effects. Frequently, the increasing of the impervious surface areas is the major cause of urban floods aggravation. For this reason, new urban drainage design concepts have been researched in the recent decades, looking for a more sustainable stormwater management approach. The concept of sustainability in urban drainage implies that floods may not be transferred to downstream and that drainage systems must be planned considering urban development along time. Storage and infiltration measures, distributed over the watershed and integrated with urban landscape, should be introduced to reduce flood peaks and reorganise flood flow patterns. Following this path, the concept of low impact development (LID) may be a reference for urban drainage projects of new housing subdivisions. This concept tends to produce built environments with minor hydrological changes, trying to preserve or recover natural flow conditions prior to the urbanisation. In this con- text, this paper aims to discuss the problems related to urban flood in a conceptual, but practical, perspective, comparing different alternatives of drainage design for urban areas in a development process. In particular, a case study in the neighbourhood of Guaratiba, at Rio de Janeiro City, Brazil, will be developed. This region is under an increasing urban growth pressure, but it is still possible to plan and design an alternative occupation. Basically, two approaches were compared: a traditional end of pipe design concept and an alternative sustainable design approach, based on the LID concept. The effects of the LID flood control measures were analysed and compared, applied in both public and private areas of a new urban subdivision project. A critical storm event was considered for the local scale and for Cabuçu River, which is the receiving water body for the local drainage system. The combined use of infiltration and storage measures was able to recover flood peaks. The pre-urbanisation values were approximately reproduced, both for the local and the basin scales, although peak times were not recovered.

Keywords

low impact development, urban site development, sustainable urban drainage, flood control, math- ematical modelling