Legal instruments as tools for flood risk and disasters reduction

Abstract

Urban flood is a frequent phenomenon nowadays, however urban densification and land sealing (consequence and probability), tend to enhance the risk of disasters. Aiming to reduce such risk, the objective of this work is to analyze how the legal instruments are potentiating or mitigating the risk of flooding in the main cities of the Itajaí river basin. To achieve this objective, we carried away a descriptive research over municipal master plans and legislations of Rio do Sul, Blumenau and Itajaí, with an intra-plot focus, analyzing the urbanistic indices: occupancy rate and permeability rate. These indices were related to the urban zoning map and quantified by city, making possible a comparative analysis. The urban zoning maps were also used to overlap the flooded area maps. Results show that Itajaí has the highest occupancy rates allowed and the lowest permeability rates required. Regarding the potential flood affected areas Rio do Sul and Itajaí have zones with occupation incentive within areas susceptible to flooding. In addition, like other intra-plot measures to slow down runoff of rainwater, only Blumenau has specific legislation encouraging the use of "green roof". Therefore, it is concluded that the municipal laws of the analyzed cities have not encouraged urban sustainability, and their urban indexes are contributing to the increase the flood disaster risk.