Dutch lead post-tsunami reconstruction in Indonesia
A Dutch consortium led by DHV is supporting the Indonesian government in the rehabilitation and reconstruction of the areas of Aceh and Nias in Indonesia affected by the catastrophic tsunami of December 2004. Strategic planner at DHV, Jeroen Alberts, explains how the company is supporting the recovery process by providing expertise in sea defence, flood protection, refuge and early-warning systems.It is nearly two years since the devastating tsunami, generated by an earthquake with a magnitude 9.5 on the Richter scale, hit the coast of Aceh in Indonesia. The fault line is about 1200km long, running from the coast of north Sumatra to the Nicobar and Andaman islands.
Within 20-30 minutes, the coast of Aceh was hit by a series of waves, with a height of 10-12m. Run-up of the wave was observed up to 25-30m high. More than 160,000 people died and more than 500,000 people lost their houses and livelihoods. In addition, an earthquake struck the island of Nias in March 2005.
The international community responded quickly, and donations and funds were raised to support the people of Aceh and Nias in their recovery from these disasters. A Dutch consultancy consortium, led by DHV, is supporting the Government of Indonesia in the rehabilitation and reconstruction of the affected areas.
Bram van de Boon of the consultants' team explains the situation: "The main challenge faced by the project is to create a safe habitable environment that enables economic recovery and sustainable development in Aceh and Nias Island. Alleviating the hardship of the people affected by the natural disasters and reducing risks of future floods is our major concern."
The DHV project includes sea defence, flood protection, refuge and an early warning system. All three fields have their specific scope and applicable technologies.
The Government of the Netherlands is funding the sea-defence project, involving about 1200km of shoreline, from Banda Aceh in the north to Singkil in the south of Aceh. The consultancy team is providing technical assistance to the coordinating organisation for the rehabilitation and reconstruction of Aceh and Nias, Badan Rehabilitasi dan Rekonstruksi (BRR).
The sea-defence strategy provides a policy framework for short and long term planning and investment decisions in the coastal zone of Aceh and Nias. This strategy aims to:
- Support livelihood recovery in the coastal zone
- Provide a less risky environment and to reduce the vulnerability of coastal communities and economy to tsunamis, coastal erosion and flooding
- Ensure a long-term sustainable coastal zone development, based on economic efficiency, ecological integrity and social equity.
Sea defence consultants are in the process of preparing and running different studies and simulation models to prepare physical tsunami protection measures. With a focus on the structural aspects with regard to wave load of tsunamis and into the effectiveness of tsunami protection measures.
Bram van de Boon explains the challenge, "Protection from a tsunami wave of about 10m high by a hard structure like a seawall or breakwater for Banda Aceh might be technically feasible, however, the total investment costs involved exceeds a number of times the total value of protected assets. The main challenge is to find an optimum mixture of hard and soft engineering solutions with appropriate safety levels and an economically justified investment package."
The packages of tsunami defence measures for different locations in Aceh will be tailored to local conditions, like economy, population and infrastructure, and will consist of a mix of measures. Soft structural measures to be considered are dune and wetland restoration, and the establishment of green belts.
Hard structural options to be considered are groynes, detached breakwaters, dikes and flood walls. Complementary solutions have to be found in land-use planning, designating safe areas, disaster preparedness and emergency planning.
Land-use planning and safe areas focus on keeping the community away from floods. However the concept of moving people away from floods is difficult to implement.
The major constraints are land titles, land compensation and loss of livelihood. The land registration system was completely destroyed after the tsunami; currently BRR and the Land Registration Department (BPN) implement a prioritised land registration programme which will run until the end of 2008.
According to BRR's masterplan of 2005, local communities have the right to return to their original locations, especially communities whose livelihoods depends on the sea, such as fishermen. A programme focusing on disaster preparedness and emergency planning will support these communities living in vulnerable locations.
Tsunami early-warning systems (TEWS)
Studies predict the likely occurrence of tsunamis along the coast of Sumatra every 30-50 years. On 17 July 2006, when a tsunami hit the coast of west and mid-Java, it became clear that communities are living in a zone in which they have to be prepared every day to deal with the threat of a tsunami.
Communities are currently rebuilding and relocated in a vulnerable area prone to potential future tsunamis. Settlement areas on peninsulas, like the cities Calang and Meulaboh, are very vulnerable to tsunami damage and casualties. There is no warning system in place for communities to prepare them for potential tsunamis
Risk reduction forms an integral part of the sea defence strategy for the coastal areas of Aceh and Nias. Tsunami early warning systems (TEWS) consist of a mixture of protection and adaptation measures for casualties and damage.
The TEWS includes warning information management, emergency response planning and public awareness raising and training. Warning information management includes:
- Upstream early warning from a buoy in the sea to a national or regional metrology and geology centre
- Communication plans
- Different alarm systems like sirens, SMS and speaker systems on mosques
- Local early warning strategies.
Infocards can be used to raise awareness and preparedness of the community vulnerable to potential tsunami.
The sea defence project includes:
- The formulation of a refuge master plan for Banda Aceh
- TEWS pilots and training for provincial authorities and other stakeholders
- TEWS public awareness plan
- SMS warning pilot
- Preparation of a Tsunami Impact Model database.
As the coastline is severely damaged, settlements are exposed to wave-overtopping, experience flooding during storms and even tidal flooding. Issues to be dealt with by the project are flooding both from the sea and by rivers.
Though the coastline is recovering, it remains unstable for many decades as it adjusts to the new conditions. Results of a morphological study show that the combination of the 2004 tsunami and land subsidence have caused a long-term imbalance of the coastal zone.
In the short-term, coastal recovery can be observed by the formation of sand bars and dunes. However, the amount of recovery is as yet very uncertain, because the amount of sand lost from the active cross-profile to deeper sea and on land during tsunami is uncertain.
Due to local land subsidence, the long-term perspective for the recovery of the coast is highly uncertain, the shoreline may move several hundred meters inland. The sea defence consultants' recommendation was to avoid the reconstruction of infrastructure and settlements within 200m of the current shoreline where possible.
Flood protection drainage
Many settlements experience localised river-flooding problems where river mouths are blocked. Drainage conditions, subsidence and tsunami damage to existing urban drains have posed serious drainage problems at many locations in Banda Aceh, Meulaboh and Lhokseumawe.
The consultants will continue to support BRR and international donors like the Multi Donor Fund by conducting feasibility studies, detailed engineering design (DED) and the preparation of tender documents for a number of coastal defence, flood protection and drainage infrastructure projects. Infrastructure Reconstruction Projects will be prepared for the cities of Banda Aceh, Lhokseumawe, Calang, Meulaboh and Gunung Sitoli focusing on the improvement of drainage infrastructure and coastal protection works.
Smaller investment projects are prepared for rural sub-districts like Lhoong and Samatiga which will focus on providing local drainage solutions and local flood protection works.
Bram van de Boon said, "Though the Acehnese community is facing an extraordinary situation and every individual mourns the loss of beloved ones, the general attitude and spirit is positive and forward-looking. It inspires our team and we are confident that we will have some major infrastructure projects up and running by the spring of 2007."