Non invasive defence structures in the urban environment: a case study

摘要

Most of the cities bordering the Mediterranean Sea experience frequent sewer overflow events due to the joint effect of inadequate combined sewer systems and the particular steep slope morphology of the urban area. moreover the historical origin of the urban texture and the morphological features make every traditional measure fitted to reduce system failures and pollutant charge quite difficult to undertake. In this study an alternative non infestive proposal is described, applied to the Historic Centre of Geneva and based on an integrated multi-objective management of the drainage system This will support waste water management and control in both ordinary condition (dry weather to moderate rainfall events) and in emergency (intense rainfall events). In emergency conditions it will be possible to control the hydraulic behaviour of the sewage network by reducing the frequency of failures through distributed water storage interventions within the urban territory and reducing damages due to flooding events. The problem of building new water storage structures is solved by the restoration of old underground man-made volumes (tanks, sinks, military and hydraulic infrastructures, etc.) in the area of the Historic Centre of Geneva in order to avoid invasive actions in that urban context. The integration of the city rainfall monitoring system at the urban scale (radar and rain garages with the implemented hydrologic and hydraulic models results into a decision supporting tool able to predict the influent volumes to the sewage network and treatment plants with sufficient lead time and provides precious information about those parameters that are required for real time control and management of the urban drainage system.