Geotechnical Report

AUSTRALIAN GEOGUIDE LR7 (LANDSLIDE RISK)

Risk to Life

Most of us have some difficulty grappling with the
concept of risk and deciding whether, or not, we are
prepared to accept it. However, without doing any sort
of analysis, or commissioning a report from an “expert”,
we all take risks every day. One of them is the risk of
being killed in an accident. This is worth thinking about,
because it tells us a lot about ourselves and can help to
put an assessed risk into a meaningful context. By
identifying activities that we either are, or are not,
prepared to engage in we can get some indication of
the maximum level of risk that we are prepared to take.
This knowledge can help us to decide whether we really
are able to accept a particular risk, or to tolerate a
particular likelihood of loss, or damage, to our property
(Table 2),

In Table 3, data from NSW for the years 1998 to 2002,
and other sources, is presented. A risk of 1.in 100,000
means that, in any one year, 1 person is killed for every
100,000 people undertaking that particular activity. The
NSW data assumes that the whole population
undertakes the activity, That is, we are all at risk of
being killed in a fire, or of choking on our food, but it is
reasonable to assume that only people who go deep
sea fishing run a risk of being killed while doing it.

It can be seen that the risks of dying as a result of
falling, using a motor vehicle, or engaging in water-
related activities (including bathing) are all greater than
1:100,000 and yet few people actively avoid situations
where these risks are present. Some people are averse
to flying and yet it represents a lower risk than choking
to death on food. Importantly, the data also indicate
that, even when the risk of dying as a consequence of a
particular event is very small, it could still happen to any
one of us any day. If this were not so, no one would
ever be struck by lightning.

Most local councils and planning authorities that
stipulate a tolerable risk to property also stipulate a
tolerable risk to life. The AGS Practice Note Guideline
recommends that 1:100,000 is tolerable in newly

developed areas, where works can be carried out as
part of the development to limit risk. The tolerable level
is raised to 1:10,000 in established areas, where
specific landslide hazards may have existed for many
years. The distinction is deliberate and intended to
prevent the concept of landslide risk management, for
its own sake, becoming an unreasonable financial
burden on existing communities. Acceptable risk is
usually taken to be one tenth of the tolerable risk
(1:1,000,000 for new developments and 1:100,000 for
established areas) and efforts should be made to attain
these where it is practicable and financially realistic to
do so.

TABLE 3: RISK TO LIFE

 

 

 

 

 

 

 

 

 

 

 

Risk (deaths per Activity/Event Leading to
participant per Death

year) (NSW data unless noted)
1:1,000 Deep sea fishing (UK)
Te 0) Motor cycfing, horse riding ,

. ultra-light flying (Canada)

4:23,000 Motor vehicle use
1:30,000 Fall
1:70,000 Drowning
1:180,000 Fire/burn
1:660,000 Choking on food
1:1,000,000 Scheduled airlines (Canada)
1:2,300,000 Train travel
1:32,000,000 Lightning strike

 

 

 

 

More information relevant to your particular situation may be found in other AUSTRALIAN GEOGUIDES:

GeoGuide LR1 - Introduction
GeoGuide LR2 - Landslides
GeoGuide LR3_ - Landslides in Soil
GeoGuide LR4 - Landslides in Rock
GeoGuide LR5 - Water & Drainage

wees

GeoGuide LR6 - Retaining Walls

GeoGuide LR8  - Hillside Construction

GeoGuide LRO = - Effluent & Surface Water Disposal
GeoGulde LR10 - Coastal Landslides

GeoGuide LR11 - Record Keeping

 

The Australian GeoGuides (LR series) are a set of publications intended for properly owners; local councils, planning authorilies;
developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a nalural or engineered slope, a cutting, or an
excavation They are intended to help you understand why slopes and retaining structures can be a hazard and what car be done with
appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The
GeoGuldes have been prepared by the Australian Geomechanics Society. a specialist technical sociely wilhin Engineers Australia, the
National peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering

geologists with a particular interest in ground engineering
National Disaster Mitigation Program.

The GeoGuides have been funded under the Australian governments’

Australian Geomechanics Vol 42 No 1 March 2007 173