slide show targets the many countries in Latin America and the
Caribbean that are vulnerable to a variety of natural hazards.
It is meant to serve as a training tool and information resource
on the basic elements of disaster mitigation in drinking water
and sanitation systems.
has been placed on the impact of disasters on such systems and
the mitigation measures that can be adopted to reduce it. The
presentation follows up on an earlier PAHO/WHO publication, Natural
Disaster Mitigation in Drinking Water and Sewerage Systems: Guidelines
for Vulnerability Analysis.
and technicians involved in the design, construction, maintenance
and management of water and sanitation infrastructure are the
intended audience of this package, which aims to promote and facilitate
the incorporation of disaster mitigation measures in such infrastructure,
reducing the damage caused by natural disasters and ensuring the
continuity of key services in their aftermath.
This training material does not exhaust all the
variables involved in reducing the vulnerability of water and
sanitation systems to natural hazards.
However, it does cover the content outlined in Slide
considerations on disasters and their impact on water and sanitation
Numerous natural hazards loom over Latin America
and the Caribbean: earthquakes, hurricanes, volcanic eruptions,
floods, landslides, and drought, to name just a few (see Slide
3). All too frequently, such disasters ravage
our countries, leaving in their wake poverty and destruction.
Consideration of recent disasters reveals an
increase in vulnerability due to man-made causes.
Both the frequency and impact of disasters have increased.
Among other consequences, water-supply and sewerage facilities
are often seriously compromised, affecting the health and welfare
of the population.
The reasons for protecting water and sanitation
systems from natural disasters range from protecting public health
to preserving the significant investments made by water companies.
The interaction between natural disasters and
water and sanitation systems has shown again and again how sanitation
systems are exposed to suffering severe damage. Moreover, development
initiatives rarely take into account the effect of natural disasters
on such systems. The results often are:
Economic losses for the water companies (see
5 and Slide
6) due to the costly direct and indirect
damage caused by disasters on such systems.
Direct effects involve the physical damage to the infrastructure. Indirect damage is linked to the additional expenses that
the water companies need to incur in order to respond to the
emergency, as well as the loss of revenue due to the interruption
of their services. Studies
carried out after the April 1991 earthquake in Limón, Costa
Rica, proved that adopting mitigation and prevention measures
needed would have cost only five million U.S. dollars, as
opposed to the nine million dollars’ tab of response and rehabilitation
efforts—a net loss of four million dollars. (See Slide
A severe degradation of the quality of the services
provided, leading to increased health risks. (See Slide
When a disaster damages water-supply systems
the impact on public health is readily apparent. One example is
the drastic increase of acute diarrheic illnesses and other water-borne
diseases. (See Slide
lists some of the reasons for the particular vulnerability of
water and sanitation systems to natural hazards, from the geographical
extension and physical characteristics of such systems to the
overwhelming importance of a reliable supply of water in emergency
The only way to ensure that such infrastructure
is capable of withstanding disaster situations is to apply prevention
and mitigation measures that reduce the vulnerability of the systems.
Often, vulnerability starts with the choice of
an inappropriate location for the system’s components. (See Slide
a given component cannot be sited in a safe area, its design and
construction must meet preventive criteria in order to ensure
continuity of services in extreme conditions.
12 shows the construction of a retention wall
to protect a pumping station from the landslides that were affecting
If for any reason mitigation measures cannot
be adopted, it is necessary to know the vulnerability of system
components to the various hazards prevalent in the area, so as
to plan an effective response in case of an emergency.
Minimum stockpiles of chemical compounds (Slide
13) and spare parts, previously identified as
essential, are crussial to effectively respond to disaster situations.
In order not to return to the levels of vulnerability
that prevailed before such an emergency—and that become all too
apparent after one has struck—preventive measures must be adopted
throughout the various stages of rehabilitation and reconstruction,
such as changing the materials used, the site of the components,
or layout of the network. (See Slide
One of the peculiarities of water and sanitation
systems is that each component might be exposed to different hazards.
Hence, measures must be taken to respond to each of the
vulnerabilities identified throughout the network. (See Slide
This slide is animated and takes about one minute to be viewed
in its entirety. It
shows the effects of different hazards on various components of
a water-supply system. The
point to bear in mind is that not all components of such systems
will be affected by the same natural hazards
Vulnerability is linked to the intensity and
hazardousness of any given event as well as to the characteristics
of the component in question. While hazards cannot be eliminated,
vulnerability can be reduced to minimize the resultant damage
and improve response in the immediate aftermath of a natural disaster.
Reducing the potential impact of such an event calls for
is directly proportional to the existing hazard and the vulnerability
of the component in question (Slide
reduction therefore requires reducing either the hazard or the
degree of vulnerability.
When natural hazards are liable to affect water
and sanitation systems, whether extant or under construction,
risk management aims to reduce the effects of a potential disaster
by taking prevention or mitigation measures. Specific measures are chosen after a vulnerability assessment
has been conducted of the various components and the hazards to
which they are exposed.
shows the mitigation measures applied to a water main. A seismic
vulnerability assessment revealed the need to widen the main’s
foundations in order to make it safer and reduce the risk
of failure due to earthquakes.