An aerial view of flooded villages around the failed dam in Laos on 26th July (source: Ben C. Solomon / The New York Times)
Last week saw devastating scenes in Laos as news reports came in of a Dam collapse which flooded villages and resulted in deaths and destruction. In the aftermath of this disaster Ambiental was called upon to produce a flood model of the event to support the relief effort. Using Ambiental’s Flowroute-i flood simulation software the flood event was recreated with computers to produce an event footprint.
The devastating impacts of Dam failure
The Xepian-Xe Namnoy dam construction project was approximately 90% complete at the time of the incident. It was set to start commercial operations in 2019 as part of a plan to build 100 hydroelectric power plants by 2020. Landlocked Laos is pursuing an extensive and ambitious goal of becoming the “Battery of Asia” and has invested billions in recent years pursuing that objective.
The dam collapse on the 23 July 2018 is reported to have occurred due to heavy rain and flooding in the region. Excess water caused too much pressure on the saddle dam, which is an auxiliary structure used to hold water beyond that which is held by the main dam. This resulted in a collapse and the ensuing flood swept downstream causing devastation in a number of villages located in the Sanamxay district in the Attapeu Province.
It is estimated that 5 billion cubic meters of water was released from the dam. It has been reported that 26 people are dead, 131 still missing and over 6000 people were displaced as a result of the flood. The disaster highlights the inherent risks in dam construction. Collapses like this are uncommon but the consequences can be devastating for those located in the danger zone.
Modelling Dam failure scenarios
Ambiental has expertise in modelling the potential consequences of Dam failure, most recently in Malaysia as part of the EASOS project, funded by the UK Space Agency. Ambiental’s Dam failure scenario models are providing the Malaysian government with actionable intelligence on the location and severity of impacts as well as revealing the timeline of flood evolution. These tools are essential for risk managers which inform land-use planning decisions and enable preparations for response and mitigation of disasters should they occur.
In Laos the impact of the flooding resulting from the Xepian-Xe Namnoy dam has been modelled using Flowroute-i™, Ambiental’s precision 2D+ hydraulic software. With this software it is possible to simulate a variety of flood-related scenarios. The technology can rapidly simulate the movement of water over a digital elevation model which replicates real-world processes of flow driven by inertia. The resulting outputs are time contoured flood footprints which describe the extent, depth and velocity of flooding.
Ambiental’s Xepian-Xe Namnoy dam failure model has been passed on to interested parties concerned with the situation. This model is being provided freely to the geospatial community in order to support ongoing relief efforts, to assist researchers and academics and to showcase capability in rapidly producing high precision flood products which provide insight prior to, during and after flood events. The products not only prove valuable to governments and aid organisations but also provide value to insurance companies in planning for and responding to loss claims.
Comparing the Ambiental model to visual reports and other sources helps to validate products and refine capabilities. The impact of the flood has been detected from space using the Copernicus satellite (European Space Agency) and the UN has mapped the affected area by comparing satellite detected surface-waters.
The left image shows the Xepian-Xe Namnoy reservoir before the disaster on 13th July, the right image shows the aftermath on 25th July with depleted reservoir and widespread flooding to the south (source: ESA)
Enabling safe and responsible risk management
Events such as these highlight the need for proactive action and foresight into the likelihood and consequences of dam failure across the world. This is particularly important given the impact flooding can cause in terms of people affected and buildings damaged.
In a historical context this recent event in Laos is relatively minor. The Benqiao Dam failure in China of 1975 is the largest event in history which caused an estimated 171,000 deaths and 11 million people displaced. Colossal dam engineering projects have occurred in recent years and many are planned for the future, which exemplifies the need to increase capabilities in mitigating the risk of flooding and reducing the vulnerability of populations potentially affected.
Through Ambiental’s capabilities we are able to demonstrate the extent of the flood footprint for any given scenario. Please contact us to access to the data presented in this report and to discuss this topic with our flood experts.
About the Author
Paul Drury is the GIS Data Manager at Ambiental. His role includes project management of production operations and reporting back to stakeholders. He also oversees the preparation, integration and quality assurance checking of data assets. Paul is an expert in GIS and data analysis with a developed understanding of the environmental data industry and underlying technical concepts. He has a BSc (hons) in Environmental Sciences from the University of Brighton.