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This 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.

Emphasis 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.

Professionals 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 1.

General considerations on disasters and their impact on water and sanitation systems (Slide 2)

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. (See Slide 4.)

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 Slide 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 7.)
  • A severe degradation of the quality of the services provided, leading to increased health risks. (See Slide 8.)

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 9.)

Slide 10 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 conditions.

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 11.)  When 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.  Slide 12 shows the construction of a retention wall to protect a pumping station from the landslides that were affecting it.

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 14.)

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 15) 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.

Risk Management (Slide 16)

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 disaster risk management.  Risk is directly proportional to the existing hazard and the vulnerability of the component in question (Slide 17).  Risk 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.

Slide 18 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.

© Pan American Health Organization, 2005