Tunnel erosion is a soil loss process that can lead to rapid and irreversible degradation of valuable land affecting both natural and man made landforms. Where natural landscapes are affected the value of grazing, farming and recreational land can be rapidly lost. In man-made landforms such as dam embankments or reclaimed land constructed as part of land restoration or urban development, the tunnels can be hazardous to the integrity of the landform, pose a risk of dam failure or cause a safety hazard to persons and vehicles.
This paper describes the characteristics of tunnel erosion as observed in a land development area in western Sydney and the measures used to identify and treat at-risk areas. The land affected is intended for residential development and had to be assessed in detail to determine whether remediation was required and, if so, then how this would be achieved. A Tunnel Erosion Identification Rating system and innovative test procedures were developed for the study that could have wider application other than just the affected landforms encountered in the study. Also, relationships were established that correlate chemical properties of the soil to the physical properties, thus reducing the need for expensive chemical testing of the soil.