Use of low impact development techniques to control hydrological impacts

ABSTRACT

The disordered urban growth has several implications for the drainage of urban watersheds, especially regarding changes in runoff. The Mãe d’água watershed in Viamão/RS in Brazil portrays well this problem. Therefore, the following issue arises: are there LID solutions compatible with the mitigation of hydrological impacts in situations of urbanization under consolidation? In this respect, simulations were performed for three different urbanization scenarios, being: the current, the future, and the possible scenarios. The current scenario represents the current system. The future scenario is represented by the implementation of the current Master Plan of Viamão, with permeability rate of 10% in the lots. The possible scenario was presented through the insertion of LID measurements (vegetative swales and permeable pavements) and with the lot permeability rates of the future scenario. The scenario simulations were performed in the SWMM model for design rainfalls with a return period of 2, 5, 10 and 20 years. The most critical scenario regarding drainage problems was the future scenario. In the possible scenario, even with mitigating measures, there are still flood volumes in some points, but the LIDs reduced the volume flowed in the watershed by up to 14% for the RP of 2 years. The LID measurements showed best performance for rainfalls with lower return period. The best efficiency in the reduction of runoff volumes was through the maintenance of soil permeability rates. However, LIDs help to reduce surface runoff, being a viable alternative for areas that are already consolidated.

Keywords:
urban drainage; hydrologic model; sustainable infrastructures