Microtunnels and Urban Macrodrainage: Two Case Studies in Brazil

Urban flooding problems have become increasingly recurrent across the world, especially in the big and mid-sized cities. Particularly in Southern Brazil, one of the most critical and high risk flooding regions is the Itajai Valley, Santa Catarina State. In fact, since 1852 there have been an increasing number of flood events, culminating in the disasters that occurred in 1983 and 2008, with great material and human losses. In order to control or minimize the potential harm of floods, urban drainage or macrodrainage systems should provide underground infrastructures (tunnels, pipelines and conduits) to drain away floodwaters. However, the intricate and densely packed urban areas pose severe limitations to the construction of such infrastructures, especially for the traditional open-trench construction methods. Trenchless or non-destructive methods, such as tunnels or microtunnels, are becoming increasingly important, if not the only viable solution. Besides the evident advantage of the much lower damage on the ground surface and other underground utilities compared to the open-trench methods, they normally require less manpower and surface transport/movement. However, these advantages may not be as widely recognized in Brazil, where manual excavation still prevails. This paper presents two studies of alternative uses of microtunnels for macrodrainage, designed to reduce flooding risk in two metropolitan areas of Santa Catarina State: Brusque and Itapema. Also, this paper shows some analysis results using numerical models to represent the corresponding construction stages of both projects.