Dam Safety – whose responsibility?

by Eng (Ms) Badra Kamaladasa

On September 10 a horrible dam disaster occurred in Libya stunning the global community with its consequences. Dam experts the world over began sharing information, opinions etc. to establish the reason for the failure. The latest figures on death or disappearance of humans are 10,000 and 11,000 rspectively. No account is available yet on other affected living species such as pets and farm animals. It would take months to estimate the damage to infrastructure and the environment. The mental scarring of those affected will not be measurable for generations, a fact noted by the scientific community.

Reuters reports that U.N. Secretary-General Antonio Guterres told the General Assembly that Derna (the disaster location) residents were “victims many times over of war, climate change and leaders – near and far – who failed to find a way to peace”. Angry residents say the disaster could have been prevented. Officials acknowledge that a contract to repair the dams after 2007 was never completed, blaming insecurity in the area for that. Engineers blame years of neglect due to political instability in the country for the failure of the two dams. By this week eight officials were jailed for negligence of their duties that caused the deadly collapse of the dams.

This whole episode reminded me of the Kantale dam breach of April 1986, more than 37 years ago. Even though the rest of the country has forgotten that disaster which took 127 human lives, totally destroyed nearly 600 private and government-owned buildings and partly damaged another 630, and washed away roads and other infrastructure.

Area farmers lost their crops. The survivors and officials on the spot can remember the devastation and agony of the aftermath. The cost of relief work and rehabilitation of infrastructure was Rs. 525 million then, which would be more than Rs. 12 billion at today’s value.

Can anyone ensure that similar disasters will not happen in the future? Whose responsibility is it to prevent or mitigate such disasters? Let us get some idea about causes of dam disasters and responsibilities of various sectors in minimizing the risks.

A dam is considered as the most hazard prone man made structure, among all civil engineering structures. Failure of a single large dam can cause the instant loss of thousands of lives, billions worth of property damage and a priceless environment cost. Many including developed countries, have faced this horrendous experience and taken action to prevent or mitigate dam disasters.

A dam can fail with or without prior warning due to an inherited weakness, a gradually developing weakening process or as a result of a natural phenomenon such as a heavy storm, landslide or earthquake.

Hence it is difficult to design a dam with a zero probability of failure. The only solution is to have a foolproof surveillance and monitoring system in place under the direction of experienced professionals.

How vulnerable are those living in the shadow of dams is a frequently asked question. Rumours are common during bad weather about dangers of dams, particularly those located at elevations above population centers, breaching. This makes people panic and look for reliable information. One basic weakness is that people are not made aware in advance of impending danger.

Preparing inundation maps and making people aware of vulnerabilities is mandatory in many countries. In Sri Lanka, reservoirs such as Samanalawewa, Senanayake Samudraya, Nachchaduwa etc are considered high risk schemes. Proper risk analysis of each and every dam needs to be undertaken with the support of scientifically proven models now available. Investigations and detailed research may need to be done with regard to dams that may be at risk due to complex processes.

Whether a dam is made of earth, concrete or a combination of rock and core material, it is susceptible to aging, similar to a living being. It has a life span which can be extended by proper maintenance, upgrading and correct operation of associated structures. If no proper attention is paid, the dam’s life span will become less than specified. Similar to human beings, dams too should be subject to proper checks/ surveillance by specialists and remedial action taken where necessary.

Statistics show that highest number of dam failures had occurred globally due to overflow during heavy storms. Hence excess incoming water has to be released safely through the spill in a properly controlled manner.

Water released from a breach of a small village tank can be sufficient to trigger a large dam failure. This is inevitable given the topography of our river basins with dams located in close proximity to each other. In the 1957/58 floods Sri Lanka experienced such a situation when 35 large, 53 medium sized and 1,500 small dams breached during a heavy storms in the NP, NCP, CP and NWP.

Spillways in large dams were upgraded after this experience by incorporating radial gates for engineers to manage the inflow and outflow of reservoirs according to pre-determined rules without allowing the water to go its own way. This is no final solution as these gates must be maintained and even upgraded to meet the changes in climate and ecology.

With changing hydrological conditions due to climate change, it has been observed that the intensity of rainfall is increasing within shorter periods. Hence water level in reservoirs too rise very fast. The reduction in forest cover in catchments has aggravated this process. Hence adequacy of the spillways need to be periodically studied to ensure safety of dams during floods.

Prior warning systems too need tightening to ensure that signs of dam failure are quickly communicated to those at risk and evacuation centers identified. As the boy scout motto says, we must ‘be prepared.’ Dam Safety cannot be a standalone program. It must be a part of the regional development strategy in in all localities.

Apart from the dam managing organizations, other government agencies using the reservoirs for functions such as inland fishing, domestic water supply, tourism etc too have a role to play in dam safety.

Decision making during emergencies must take into account the risks to the public as well as economic, environmental, social, and cultural impacts. The technical analysis of risks associated with a dam cannot be the sole decision-making factor. All stakeholders should participate in finalizing emergency preparedness plans. Inputs on all aspects are necessary when a warning is issued. Prevention of disaster and mitigation of impact can be achieved only through such collective action.

When people use reservoirs for bathing and washing, they must restrict themselves to designated places without disturbing the bund slope or riprap. Earth bunds should not be selected for tree planting campaigns. Trees can do much harm to the integrity of a dam.

Encroachment of dam reservations and blocking the inspection paths is a very common in Sri Lanka. While it is the responsibility of the engineers to make sure dams are kept healthy, government support like funds for regular maintenance and that of other stakeholders and the public is necessary to achieve desired results.

Ultimate responsibility for a national disaster directly rests with the president/prime minister of a country whether the dam is publicly or privately-owned. This is why the president chairs the National Council for Disaster Management (NCDM), according to the Sri Lanka Disaster Management Act No. 13 of 2005.

(The writer is a retired Director General of Irrigation)