The first three questions relate to the hazard event H itself. The other questions focus on human
interference with the event1. The third question, “Where might the event take place?”, usually
results in one or more hazard maps that provide a graphical classification of the area into
different hazard zones that experience a certain risk. As said before, it is impossible to decrease
H for natural hazards. Mitigation therefore focuses on limiting human exposure and
vulnerability.
2.2 Mitigation measures and their effectiveness
Many different mitigation tools can be used in order to create a disaster resistant community.
They can be divided into land use regulation tools, construction measures, awareness projects,
hazard disclosure and financial impulses. The first two groups of tools are true mitigation
measures, the last three are measures that aim to incite people to mitigate natural hazards.
Construction measures are often referred to as structural mitigation, and land use regulation
tools as non-structural mitigation. (Godschalk e.a. 1999).
2.2.1 Structural mitigation
Structural mitigation is the most used method of mitigation. It includes for example the
construction of dams, dikes and seawalls that aim to reduce the probability of flooding.
Stormwater facilities can guide a contingent surplus of water to detention basins where it will
not cause any damage, or at least not as much as it would if been left to flow freely. These
constructions, and land improvements such as beach replenishments, restoration of sand dunes,
brush clearing, erosion controls and slope stabilization, are effective in reducing flood,
liquefaction, wildfire or other natural hazard damage, but can also be extremely expensive and
require regular maintenance (FEMA 1997, Godschalk e.a. 1999).
Another group of structural mitigation measures are building design codes. These aim to
impose a basic construction standard that can withstand a possible flood, a hurricane, or an
earthquake. Every type of hazard demands a specific type of building codes. Building
elevations for example can protect against floods, storm shutters against heavy winds and the
bolting of buildings to their foundations against severe ground shaking in case of an earthquake
(Beatley & Berke 1992). Nelson and French (2002) suggest that building codes are not an
1 Cutter (2005) distinguishes risk assessment (which focuses on the natural hazard) from hazard analysis (which
focuses on vulnerability, exposure and mitigation). Because this classification does not correspond with the
definition of risk and hazard used in this paper both procedures are gathered under risk assessment.