Overview
Earthquakes
Areas that are most sucepptible to damage from earthquakes are determined by proximity to fault lines as well as the resistance to liquefaction of the surficial material on which buldings are built upon. The intensity of quakes are strongest near fault lines and decrease with distance. Soil liquefaction happens when loose saturated soils change from the form of solid soil to the consistency of a heavy muddy liquid due to the shaking from the earthquake which increases the pore water pressure in the soil. Liquefaction reduces the shear strength of the soil, and increases its succeptibility to deformation. This can lead to sudden loss of support to buildings on the liquified soil and cause irregular settling damaging buildings and underground utilities. Areas most succeptible to soil liquefaction have loose unconsolidated soils such as loose sands, silt and clay. Younger deposits are also more likely to liquify than older deposits.
Landslides
Landslides generally happen on steep slopes. Factors that affect the succeptiblilty to landslides include the steepness of the slope, and the underlying material. The proximity to water bodies and fault lines increases the risk to landslides as well the extent of damage caused. Proximity to water bodies can affect landslides by increasing the distance they flow as well as the increase the likelihood of a landslide. Water can have a lubricating effect to both stationary and moving particles, reducing the coefficient of friction and allowing the landslide to start, and to progress for a longer distance. This is described in the article Landslide Mobility and the Role of Water by F. Legros. Streams and rivers nearby indicate that there is infiltration of water into the surrounding soil, and that the surrounding soils have reached or nearly reached its infiltration capacity, allowing for overland water flow instead of underground flow. Saturated materials have a higher likelihood for landslides to occur as water increases its weight. Weathered bedrock generally has much less cohesive strength and have a higher tendency to cause landslides.
Flooding
Flooding occurs in low lying areas that are close to water sources that can change in water level such as rivers and streams.