Surface water drainage systems to manage environmental consequences of development : An application to industrial estate development in Sri Lanka

Abstract

Sri Lanka is fast moving into an era of rapid industrialization. One aspect of the government's industrial policy is the establishment of Regional Industrial Estates, which are to be well-designed and equipped with pollution control and properly-developed infrastructure facilities.

The Karanawanwatta site at Dankotuwa in the northwestern province of Sri Lanka, is one of the sites identified for development as an industrial estate.

As part of the effort to ensure proper infrastructure facilities for the industrial estates, it is important to foster environmentally-friendly sustainable development. The infrastructure development activities of the estate will change the land cover and the drainage pattern. Such changes increase the volume and velocity of runoff, creating less groundwater recharge and more erosion and higher peak flow during storms.

These changes affect natural streams and dug wells downstream from the site, and could also threaten the sustainability of flora and fauna in the riparian environment. Increased runoff coefficients due to the industrial estate development activities may result in rapid releases of stormwater, which lead to higher downstream flood levels and longer inundation periods than experienced prior to the development of the estate. These cause inconvenience and even direct harm to downstream occupants.

This paper describes simple, low-cost engineering solutions that were recommended to be incorporated in the development plan of the Karanawanwatta industrial estate to ensure mitigation of the environmental impacts of stormwater.