Landslide risk reduction, Dark View US$35,000
This site is a small community located on a high-risk slope, which has evidence of instability, significant surface and sub-surface water flow. There is water supply to the unplanned housing on the site but no drainage provision or management surface water. The slope comprises a hollow in plan form, with potentially significant convergence of soil water, leading to locally high pore pressures and slope instability. A church on the slope, towards the central axis of the slope had experienced major structural failure as a result of slope inability.
Without interventions further failures must be expected. The intervention plan calls for a major drain approximately down the axis of the slope plan convergence, together with two intercept drains. The importance of capturing slope water behind the properties and draining that to the intercept and main down-slope drain is important; there was clear evidence of water passing under properties and causing significant failures at the downslope [front] edge of properties. This water flow, can and should, be arrested and managed.