Chosica: Prevention Bears Fruit

The landslides (known locally as huaycos) that fell on settlements along Peru’s central highway on February 15, 2009 were nothing new, yet we are now able to extract some preliminary lessons from this extremely frequent problem.

Huaycos occur almost every year between December and April. They are caused primarily by the mountainous terrain along a swath of land that rises from under 1,000 to over 3,000 meters above sea level in only a few kilometers. Usually, rainfall in this area is relatively moderate. However, every 10 to 15 years certain atmospheric conditions occur that bring clouds over the mountains from the jungle, resulting in torrential rains in the upper reaches of streams that flow past villages located along their banks. These rains fall on enormous masses of fragmenting rock that are very unstable, causing them to slide down the hillsides into the riverbeds and hit populated areas.

The landslides people remember the most coincide with the El Niño phenomenon —in 1925, 1983, 1987 and 1998— but this year’s landslides occurred in the absence of El Niño. In 1925, the Rimac River reached its historic high flow due to mudflows (500 m3/sec), flooding large areas of what is modern-day Metropolitan Lima. In 1983, landslides destroyed hundreds of homes along the central highway, and buried several villages and Las Quiscas recreational area in Santa Eulalia. In 1987, seven huge landslides in Chosica coinciding with El Niño buried 500 houses and left 200 people missing. The streets of Chosica and the central highway were filled with mud and rocks, some the size of a normal bedroom. Recently, we were able to visit El Pedregal, the hardest hit area, where the local people have rebuilt their homes on top of the ones that were buried, which in some cases are now being used as basements.

In all these disasters, people talked about the lack of prevention. Finally, after what happened in 1987, a radical change took place. Now we have evidence of how flood prevention measures taken in the last decade have limited the destructive effects of these avalanches of mud and rock. First, even though the flow of the Rimac River on that Sunday on February 15 (97 m3/sec) was greater than on March 3, 1994 (92 m3/sec) — which flooded the port of Callao, destroying 427 houses, and affecting industrial facilities and close to 10,000 people—, losses were comparatively low. This can be explained by the flood protection works built along the river since 1989 and the maintenance of the riverbed near Callao. Second, this time the mudflows in the Chosica streams (Quirio and Pedregal) carried smaller-sized rocks at a lower velocity than in 1987 because of the water flow regulation dikes built by the municipality, the Center for Disaster Prevention and Research (PREDES) and the Ministry of Transportation between 1990 and 1999. Today, we lament the disappearance of three people and the damage to some 50 homes from huaycos of similar proportions to those in 1987, but in this case a disaster that could have been similar or greater to that one was prevented.

But prevention works were not the only thing that brought security to the towns in Chosica over the past decade. Community leaders also reacted before the rains came and called the mass media to demand such works. In addition, communities were involved both through local work days and in developing the agreements about measures to be taken. The electric power company refused to install household service unless a home was located in a safe area. The media informed about the takeover of lands along riverbeds for homebuilding, and unscrupulous real estate developers were sued by the Peruvian National Civil Defense Institute (INDECI). In addition, active citizens’ oversight led to uncovering corruption in some of the river defense projects.

All of the above led Chosica to be recognized as an example of how a community can prevent disasters, and its experience was shared by the United Nations at the 1994 World Conference on Natural Disaster Reduction, held in Yokohama.

Today, the situation is becoming particularly hazardous again because there is evidence that the dikes have come to the end of their useful life and complementary projects have not been completely built. This makes us think that when new huaycos occur, we might end up bemoaning increasingly greater destruction. Furthermore, the gullies in the slopes next to settlements have not been treated for many years and new houses have been built in these areas. Finally, reservoirs and channels above the villages are not sufficiently protected.

Community organization around civil defense has grown weaker and the different agencies and official institutions involved do not seem to have the capacity to respond. Calling on local residents to establish early warning systems and evacuation routes and areas is all fine. However, these measures would be much more effective if the people and the bodies involved prepared ahead of time and were able to include risk reduction in the plans and budgets of the different public and private institutions. The great challenge now is to respond to an emergency, recognizing that the prevention measures of the past have run their course and that we need to develop new policies and strategies to reduce risk.

For furter information please contact:
Pedro Ferradas
Gerente del Programa de Prevención de Desastres y Gobernabilidad Local.
Soluciones Prácticas ITDG.