Safety coefficient
See Factor of Safety.

Scenario
A unique combination of states. A scenario defines a suite of circumstances of interest in a risk assessment, for example loading scenarios or failure scenarios.

Sensitivity analysis
An analysis to determine the range over which the result varies, given unit change in one or more input parameters.

Shear strength
The internal resistance (force per unit area) offered to shear stress. It is measured by the maximum shear stress that can be sustained without failure.

Shear stress
The force per unit area within a body of material which tends to cause two adjacent parts of the body to rupture and slide past each other.

Snow avalanche
A gravity-driven mass of snow moving down mountain slope. A moving avalanche may also contain soil, rock, vegetation or water, but by definition the initial failure that triggers an avalanche occurs within the snowpack or at the interface between snow and subjacent terrain. Avalanches range from a harmless trickle of loose snow descending to a new angle of repose to a huge and devastating mass of snow moving at high speed down a long steep slope, with enough energy to destroy everything in its path. Snow avalanches automatically reload with each snowfall and can fire several times in a given year.

Societal risk
The risk of widespread or large scale detriment from the realisation of a defined risk, the implication being that the consequence would be on such a scale as to provoke a socio/political response.

Soil conditions
The conditions of earth (moisture content, desegregation density, etc.) that may mitigate or intensify disaster agents, such as drought, flooding or landslides.

Soil creep
The gradual and steady movement of soil and loose rock material down a slope that may be gentle but is usually steep; it is also called surficial creep.

Soil moisture
Content of water in the portion of the soil which is above the table water including water vapour present in the soil pores. In some cases refers strictly to moisture within the root zone of plants.

Stakeholder
A person or an organization that has a legitimate interest in a project or an entity.

Standards-based approach
The traditional approach to engineering, in which risks are controlled by following established rules as to design events and loads, structural capacity, safety coefficients and defensive design measures.

System
Assembly that consists of interacting elements.

System response
How a system responds. May be expressed as a conditional probability of failure, to a given scenario of applied loads and concurrent conditions (see also fragility curve).

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