In recent years a steady trend toward urbanization has created new and unforeseen problems for built-up areas all over the country. The process of artificially creating non-porous surfaces such as tarmac and concrete over the majority of the ground area within the urban environment has upset a balance that has existed for millennia. This balance involves precipitation, drainage and the water table. With the extensive use of impermeable surfaces in towns and cities, water is no longer able to return to the ground as easily as it once was. The result is the creation of a lot of surface water and sporadic flash flooding in certain areas.