A Geomorphic Approach for the Design of Drainage Systems on Reclaimed Mine Areas

2004

Les Sawatsky, Femi Ade,

Effective drainage systems are required for mine-disturbed areas after mine closure and during reclamation to control surface water runoff and avoid excessive erosion. For the conventional structural design approach, armouring material necessary to satisfy the design criteria should not move during the design flood event since displacement would uncover the erodible underlying materials. This paper discusses an alternative geomorphic approach for designing drainage channels and watershed landscape. The approach is based on quantitative studies of geomorphic processes operating in a watershed. A design based on the geomorphic approach replicates the configuration, channel regime, sediment volume and hydrology of natural and mature drainage systems. Movement of some armouring material is acceptable in such an approach because the channels are allowed to mature by natural degradation and aggradation, with erosion rates comparable to the natural environment. The key advantages of a geomorphic approach over a purely structural approach include reduced sizes of armouring material, geomorphologically sustainable landscapes, “walk-away” or maintenance-free design and reduced liability in the future. Possible disadvantages include greater quantities of armour or sub-armour material, depending on the composition of the underlying material. Using the example of a coal surface-mining operation at Centralia, U.S.A, the paper discusses field data collection, design criteria, typical design details, construction methods, and constraints imposed by the “mine dump” design.

Keywords: Reclamation, Erosion Control, Drainage systems, Geomorphic Approach, Mining