Avaliação da drenagem superficial da microbacia urbana do riacho Maratoan, município de Crateús, Ceará

Abstract

The planning of urban drainage of surface water in the municipality of Crateús has presented frequent failures in its drainage systems, marked by occurrences of floods. This study aimed to analyze the urban surface water drainage system and identify critical points of flooding in an urban watershed in the Locality of Maratoan, a neighborhood in the city of Crateús, Ceará. The Storm Water Management Model (SWMM) software was used for the hydrological-hydraulic simulation of the watershed, requiring as input data the rainfall, area and width of the sub-basins, slope, waterproofing values, roughness coefficient by the Manning number ( n) and the curve number (CN). Three scenarios were simulated to understand the hydrological-hydraulic characteristics of the watershed and to help predict impacts caused by heavy rains. The first waterproofing scenario was for current watershed conditions; and the other two, for the increase in 20% and 40% of waterproof coverage. The historical series of 30 years of precipitation in the region were used, as well as maximum rainfall of 100.1 mm, 139.8 mm and 164.9 mm for the return times (TR's) of 05, 20 and 50 years, respectively. The simulations illustrated nine results that explained the dynamics of maximum rainfall with increasing waterproofing with inflows that reach up to 1898.3 m3.s-1. Representations created showed overload in the stream segments that enter the urban area, with overflow areas that justify the occurrence of floods. There was a small difference between the peak flows when applied to the same scenarios, indicating that the watershed is already saturated and in a critical state. The inflows grow linearly for each analysis, both due to the decrease in permeable layers and the increase in precipitation, as well as the dampening of flows due to the network of reservoirs present in the microbasin, which acts in the control of floods upstream. The Maratoan territory in the city of Crateús, Ceará, presents stress points in its urban surface water drainage systems, so that from the first moment there were floodable areas in the natural surface drainage network of the region for the maximum simulated rainfall.