Warning signs that say mass movement is likely to a tear include cracks resulting from tension in buildings and in the ground, tilted structures, bulging walls and steep slopes, especially with deposited material above them. Arcuate shaped cracks on ground above cliffs indicate the sites of future slumps. Once noticed the slopes can be closely monitored for change.
Large moving masses like Man Tor's landslip are monitored by GPS and laser surveys to determine the amount of movement each year of a number of fixed markers on the surface of the landscape. GPS measures distance and direction very accurately. Arrows are then drawn on a map to show the direction and length of annual movements. By comparing movements with rainfall it may be possible to determine how much water the slope can hold without moving.
Rainfall and changes and soil moisture are also monitored. Measures in boreholes indicate changes in groundwater content and the pressure it exerts; the weight of additional water can trigger mass movement. Many drainage pipes have been placed in the Man Tor landslip to remove water and reduced movement.
Comments
No comments have yet been made