SEA WALL

Indonesia 2018 | TRANSPORT & INFRASTRUCTURE | B2B

Lest they submerge the capital, the race is on to find sustainable long-term solutions to Jakarta's chronic water needs, whether that is getting dirty water out or keeping sea water from getting in.

Tim Jeanné
TIM JEANNÉ
Director Water Asia Pacific
Royal Haskoning DHV
Victor Coenen
VICTOR COENEN
Director
PT Witteveen+Bos Indonesia

What are some of the key infrastructural challenges facing the country?

TIM JEANNÉ The major challenge of the country is that there is massive economic growth paired with unprepared infrastructure. It is not just roads and railways, but also ports and airports, electricity infrastructure, power, energy, water supply, and waste water treatment. You can build a port, but without a hinterland connection or transport means to the rest of the country, you cannot go anywhere. The major challenge will be to really develop infrastructure holistically across the country, which then can be a catalyst for growth.

VICTOR COENEN All of the water in the entire city of Jakarta and upstream is polluted, as there is hardly any waste water treatment. If we drain that water into reservoirs, we will get black lagoons. With the large sea wall, there will be a large lagoon with poor water quality. Likewise, with a medium or small sea wall, there will be smaller, but numerous, polluted reservoirs. Actually, cleaning the water systems should be part of any flood management scenario for Jakarta. Some critics insist on a natural defense for Jakarta, such as repopulating the mangrove swamps and forests along the coast; however, that will not protect Jakarta from three- or four-meters-high seawater. The situation is already out of control, and the sea is now already 3m above street level. No natural system can protect the city in such circumstances; the sea would simply run right through the mangroves. However, there are certain areas where natural solutions can provide protection, and we are also working on those solutions like restoring the mangroves in central Java, for example. Where possible, we go for the soft solution, the natural solution. However, unfortunately for Jakarta, the situation is already out of control, with water overtopping the sea wall at high tide, which cannot be stopped by planting trees. We can only stop that by stopping land subsidence and strong sea defenses. That being said, constructing sea walls takes years.

How is progress coming along on Jakarta's Giant Sea Wall?

TJ We are part of this MoU and are supporting the Indonesian government through Dutch funding, to map out this masterplan for the national coastal defense. The city is sinking at a pace of about 10cm per year so large parts of the city are already well below sea level. We are already working on the 'no-regret' measures to ensure the safety for the coming 10-15 years, which includes a close-to-shore defense wall that is currently under construction. For the next 100-150 years, there needs to be a more sustainable solution to prevent flooding in Jakarta. It is not just the whole system of armoring the city against a rising sea level but also making sure that there is sufficient retention capacity in the city during the rain season. The city is now very densely built with hardly any space left for drainage canals and storage basins. Drainage canals and some of the rivers will discharge into Jakarta Bay, and it should be ensured that this water is not polluted. We see that the current administration understands this holistic approach and supports various initiatives.

VC Indonesia faces a tough decision, namely the medium- and long-term flood protection strategy for the metropolitan city of Jakarta. The construction of a sea wall seems likely, but there are discussions on timing, location, and the design lifetime. However, there is no discussion on the need for immediate protection. Part of this short-term protection is to heighten the existing sea walls by 2.5m. The construction work has already started and the first districts will be protected this year. However, in some places the city is sinking at a pace of 20-25cm a year. In those parts, the wall will only protect the city for the next 10-15 years and the question is what to do after that. There are now two options on the table: a medium-sized sea wall that will protect the city for 30-40 years (if the sinking is not stopped) or a large sea wall that can protect it for 100 years (with or without sinking). It is a matter of funding, and the discussion continues. We hope to receive the final answer soon because currently there is a Korean and Dutch technical team waiting to detail the sea wall, be it the medium-sized one or the large, original one. The medium-sized one would cost USD6 billion, while the large one would require USD10 billion. Of course, protecting the city is not just about building a wall; there are other expenses and infrastructural necessities to consider as well, such as revamping the drainage system in the city, upgrading the water supply system, cleaning all the water in Jakarta, and more. When we add this all up, the long-term cost could easily be doubled.