Surface water assessments - critical for effective landform design

摘要

Surface water impacts can represent a significant long term mine closure risk in general and for landform design specifically, particularly in arid environments due to a range of factors including erosion, geotechnical instability and changes to geochemical conditions associated with water movement through landforms. Undertaking targeted surface water closure assessments during the landform design phase can provide an effective mechanism to define and manage drainage risks. Surface water assessments utilise a hydrological model to determine the runoff generated from catchments under design rainfall conditions in order to develop a hydrograph as an input into a hydraulic model. The hydraulic model assesses the performance of the surface water controls under the modelled conditions. The surface water assessment should be informed by the critical return period for any given site. Effective waste rock characterisation provides inputs for modelling the as-constructed hydraulic properties and an indication of how these properties may change over time. Surface water assessments are critical to develop closure designs that minimise the need for ongoing maintenance, are geared towards the achievement of long term closure objectives and are better able to meet stakeholder expectations. These assessments can provide key information to the landform design process, including drainage controls, storage features, slope configuration, upstream runoff management and armouring specifications. This paper explores the technical aspects of undertaking surface water assessments and provides practical working examples.