Cities located on steep terrain face a daunting problem after an earthquake or landslides: the city could suddenly run out of water, at a time when people need it most.
Tens of thousands of city residents would need water for drinking and sanitation. There would also be an immediate water need to put out fires that commonly occur after earthquakes. Without water, hospitals would not be able to function well or care for the injured. Disease outbreaks would likely develop.
This could last for several days or extend into weeks in areas that are difficult to reach.
Dense construction in Shimla, India contends with steep terrain and landslides.
Photo: Navneet Yadav
We worked with two Indian cities—Aizawl in Mizoram state, and Shimla in Himachal Pradesh—to identify ways to protect their water systems. Both cities are at high risk from earthquakes and from continual landslides, particularly during monsoon season.
Water infrastructure in hill cities is especially prone to damage and especially challenging to repair. The system must cross steep terrain and pump water from sources at much lower elevation. Components are exposed over rugged terrain for significant distances.
Earth shaking can damage pump houses, water treatment systems, and power networks that run them. It can trigger hundreds of landslides in many places at once—damaging pipelines and tanks, causing debris to clog intakes. Extreme rainfall may result in wide-spread landslides over days or weeks.
Example of a water system that must traverse steep, remote terrain to supply the hill city.
Landslides not only damage the water system but also block roads that would bring repair crews and parts. People could be isolated without access to water.
What can be done? Plan ahead. With support from the Global Facility for Disaster Reduction and Recovery (GFDRR), we designed a knowledge exchange program between India and the U.S. Participants included officials from both of the hill cities and states, others in India who play a role in the water systems, and resilience professionals from both countries.
The U.S. participants, for example, shared lessons learned from impacts to the Los Angeles water system following the 1994 Northridge earthquake and resulting landslides. Those damages highlighted the importance of ductile pipes and connections to minimize breaks.
A tank in the water supply network for Aizawl, India.
The team outlined strategies to make water supply systems in hill cities more resilient to earthquakes and landslides. A near-term priority is to develop an emergency response plan particular to the water supply system, and to practice it with regular drills.
It was also recommended to create a scenario that shows likely, specific earthquake impacts, so the city can plan how to reduce risks before a disaster. Another recommendation was to create landslide hazard maps, so the city can identify high risk areas in the water system that need greater protection. In the longer term, regulations for slope excavations can control this common and preventable trigger for landslides.
Despite Aizawl's main hospital location in a moderate landslide hazard area (yellow), its water supply lines traverse high and very high landslide hazard areas (orange, red). Credit: Landslide Hazard map by Lettis Consultants International overlaid on Google Earth
Maintaining access to water after a disaster is not only possible but critical. The way forward starts when cities clearly understand their local risks and identify opportunities to make their city safer. It may take years to recover from disasters, but such planning efforts can prevent losses in the first place.
Veronica Cedillos, President & CEO
Bhutan · Dominican Republic · Haiti · India · Nepal · U.S.A.