Mass Movements Prevention,Mitigation and Protection
Table of Contents
Various methods can be used to reduce or protect people from mass movements. In addition, some methods stabilize and lessen slope stress and therefore mitigate mass movements altogether.
Prevention /Mitigation Methods
Terracing
Terracing involves the shaping of slopes into steps. Therefore when mass movements occur the waste is captured and accumulates on the flat steps and impeded from readily sliding or flowing down the slope.
Afforestation
Trees bind the soil from moving and can also intercept and slow down mass movements eg earthflows.
Wedging
Wedges are strong walls or objects that redirects mass movements to other areas. The main purpose of wedges is to protect a particular area from mass movements such as mudflows or avalanches.
Wedges on mountain slopeGeomates
Geomates are grass mates that are embedded on the surface to avoid excess soil movement and reduce rainsplash impact.
Drainage Observation
By observing drainage patterns and routes, measures such as stream diversion to restrict water from vulnerable slope areas or restrict undercutting of rivers can prevent mass movements from occurring. Pipes can be inserted along the slope so that water readily leave the slope and prevent liquefaction of soil.
Slope Stabilization Methods
These methods involve stabilizing and reducing stress and strain on the slope and therefore mitigate mass movements
Afforestation
Trees help to bind the soil together and stabilize slope movement.
Slope Leveling
Leveling slopes means flattening slopes to reduce mass movements.
Bolts/Nails
Slopes especially rocky ones can be nailed along cracks or failure planes to stabilize movements.
Cementing/Shotcrete
Fractures along the slope can be plastered with cement to stabilize movement.
Protection Methods
Methods to protect people from mass movements
- Retaining walls on slope foot
- Wire nets on slope base
- Base trenches to capture rock falls
- Wedges to redirect mass movements
A boulder catching net on a trail at Multnomah Falls, Oregon, USA, photo by Dar-Ape
Warning Measures
- Springs, seeps, or saturated ground in areas that have not typically been wet before.
- New cracks or unusual bulges in the ground, street pavements or sidewalks.
- Soil moving away from foundations.
- Ancillary structures such as decks and patios tilting and/or moving relative to the main house.
- Tilting or cracking of concrete floors and foundations.
- Broken water lines and other underground utilities.
- Leaning telephone poles, trees, retaining walls or fences.
- Offset fence lines.
- Sunken or down-dropped road beds.
- Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content).
- Sudden decrease in creek water levels though rain is still falling or just recently stopped.
- Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb.
- A faint rumbling sound that increases in volume is noticeable as the landslide nears.
- Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.