A failure in drainage system can induce in urban areas frequent inundations of underground floors or extension of local damps. It can be observed other more dangerous events as:
- Groundwater fluctuations (rise and decrease in short and medium time due to heavy rain, economical and social changing, civil and industrial variation of withdrawals, seasonal variation of irrigation).
- Salt water wedge shape aquifer during pumping test closer to coastal area
- Hydrogeological instability nearby river bank with an increasing deterioration of water quality (piping and subterranean erosion or stagnation point that could make drainage system not functional.
These environmental problems are caused by uncontrolled development of some anthropogenic factors: heavy withdrawals during time, seepage irrigation. Much of the surface of urban areas is impermeable due to roads, buildings and surface coverings. Because of this covering, the recharge is reduced and the direct runoff has increased.
These problems could occur both in Italy and in the world; with different problems and hydrogeological settings, different drainage systems are designed; In Romania, e.g. Galati city (Zamfirescu F., 2003), an increasing groundwater level caused by a loss of industrial and civil system water during the last 20 years is within5 meters. The problem could be solved with an horizontal drainage system pumping well useful for the low hydraulic conductivity and anisotropy vertical settings. A similar example isKuwaitCity(Muhammad F., 2001) where the proposed solution is given by a vertical and horizontal wells system for having about2 metersdrawdown.
Further interesting situation are observed in Italy; least but not last it is better remind the case of Buenos Aires City (Finotti R., 2007)where a salt water encroachment is caused by a coastal water pumping system. The problem solution could be a better management of withdrawals. InLondonan increasing rate of about1 meterper year is due to a heavy de-industrialization process.
InMilanwhich is one of the most city where the drainage system is required, there are both a piezometric rise level and an unsuitable water flow net (Beretta et alii, 2006).