Answer to Question 1Water is very important in landslides, so increasing surface and subsurface drainage of a hillside will
help stabilize the slope. Drainage serves two purposes: It reduces the weight of the material likely to
slide and increases the shear strength of the slope by lowering pore pressure. Surface waters can be
drained or diverted by ditches, gutters, or culverts. Drainpipes driven into a hillside can remove
subsurface water. Planting vegetation on hillsides helps stabilize slopes by holding soil together and
reducing the amount of water in the soil
Answer to Question 2Slope-stability maps are used to determine where certain types of buildings and other structures should
or should not be built, and to indicate how slope stability might be improved, if structures are built
where stability is compromised.