Storage measures as compensatory techniques for urban lowlands flood control

Abstract

Urban flood problems are being aggravated in growing cities. The process of urbanisation generally tends to supress natural retention areas, removing natural vegetation and producing large impervious areas. Besides, the traditional urban drainage approach, comprising mainly canalisation measures, showed to be potentially unsustainable, tending to transfer floods to downstream. Gradually, in the past recent years, this practice has been complemented or replaced by new concepts considering the use of distributed interventions to approximately recover flow patterns prior to the urbanisation. In Brazilian great cities, drainage systems' design started to incorporate the use of the so-called Compensatory Techniques, which aim to compensate the effects for the urbanisation process over the water cycle. In this context, detention and retention reservoirs have been conceived as potential adequate solutions. Departing from a Municipality proposition for a new urban development in Guerengue River catchment, west zone of Rio de Janeiro, and considering the concept of compensatory techniques applied to the urban drainage, an alternative configuration for the drainage system is proposed in the catchment scale, and compared with the critical present situation. In this alternative proposal, besides the Municipality actions, a complementary set of storage measures distributed along the riverine areas was considered. Additionally, local measures, composing multifunctional landscapes on the microdrainage scale, were also introduced to face local inundation problems. The scenarios assessment was supported by mathematical modelling. Modelling results showed that, at present situation, great part of the catchment suffers from flooding, with water depths that usually range from 0.15 m to 1.50 m. In critical areas, flooding may surpass the 1.50 m high level. The introduction of the compensatory techniques was capable of significantly changing this situation. However, for a more effective result, land use planning must also be addressed in the context of flood control. Keywords Compensatory techniques on urban drainage, flood control, mathematical modelling, MODCEL, storage measures. Language: en