1) We should avoid construction
in areas that are prone to mass movements.
--Avoidance of unwise building development requires good zoning regulations based on adequate geological assessment of the terrain.
--A geological survey will quickly reveal the conditions in an area that make construction unsafe, such as poorly vegetated slopes covered with unconsolidated material that absorbs water easily.An example
--In some areas where slopes and materials are unstable, the effort and expense required to engineer safe structures would be so great that the areas would be better off undeveloped. A typical case.
--In other areas, no amount of engineering will counter nature's tendency for mass movements.
2) Where slopes are naturally
stable, we should build in a way that does not make them unstable.
--Architectural and landscape design can help ensure that relatively stable areas are not made unstable by stripping the vegetation that binds the soil or by artificially oversteepening the slopes. Such designs must adapt construction plans to lit the natural situation.
--If vegetation must be eliminated and slopes steepened during construction, the area should be properly graded with a low slope and replanted soon as possible.
3) Because saturation is
a critical factor, we must engineer water drainage so that slope materials
will not become waterlogged and likely to slide or flow.
--One essential measure is preventing a buildup of water in poorly drained soil or other unconsolidated materials. Slopes that are otherwise stable may creep or slump after heavy rains if retaining walls or the construction itself prevents drainage of the water (see illustration). --In areas where heavy rains tend to continue over long periods, storm drainage of potentially unstable slopes is vital.
--Good sewer systems are also part of slide prevention. A frequent culprit when soil becomes waterlogged is poorly designed drainage from septic tanks in a hillside home development.