Standard design of hydraulic structures in urban drainage systems

In the year 2005 Italian Ministry of University and Research financed a national coordinated project on the subject: Standard design of hydraulic structures in urban drainage systems, that gives the title to this book. Four operating units based in Napoli, Roma, Catania and Cosenza were involved, leaded by Prof. Giacomo Rasulo as coordinator. The main idea of this volume was to spread among interested audience the activities carried out during the project in a coordinated way: as a matter of fact, papers concerning researches developed during the project activities have been submitted to refereed journals or presented at national or international conferences, and the overall project achievements could possibly be appreciated in a limited way. In this sense the outcomes of activities have been here presented to give an overall view of this coordinated project. Objective criteria to verify urban drainage systems became necessary after ATO (Optimum Territorial Range Agency) institution in order to define upkeep programmes and actions to restore the existing structures. Moreover new hydraulic structures might be designed to ensure the proper hydraulic working of city sewerage. In Italy standard designing criteria for structures used in urban networks are rarely available. On the contrary in other European countries designers and city sewerage managers can consult extremely useful designing criteria defined by specific Standard Agency (German ATV, for example). Hydraulic structures design, when designing criteria are not available, generally develops in two steps: 1) designers dimension structures following their own experience and considering indications available in technical literature; 2) expensive laboratory tests are performed on physical models to verify the previously dimensioned structures and to complete their designs; only the second step has to be considered when structures have to be verified. The aim of this book is therefore to define a "proper design" manual to analyse in detail some of these structures and to give useful indications to designers and managers. The hydraulic structures analyzed have been split into four sub-themes as the number of operating units: - vortex shafts ; - energy dissipative structures in steep sewers; - devices structures for sediment removal in sewers; - pollution indicators for best management practice structures. Study results concerning the vortex shaft structure allowed to define the inlet structure for supercritical flow approach channel. Laboratory measurements combined with numerical simulations have been performed to analyze the hydraulic behaviour of channel drop inserted in a sewer, equipped with a depressed stilling basin. Experimental and numerical analysis of the hydraulics of flushing waves were performed to analyze both the outflow processes and scouring effects. Sewage quality in a combined sewer system were studied in order to obtain some pollution indicators in dry and wet weather condition as helpful in providing the best management practices to reduce and control the impact of discharges on the receiving water bodies.