Case study: Jakarta – the sinking capital
Jakarta’s severe flooding is happening more often and with more intensity. This is one of the many environmental challenges confronting the Indonesian capital that prompted the government of President Joko Widodo to announce in 2019 a plan to move the seat of the federal government to a new city to be named Nusantara that has yet to be built in the province of East Kalimantan on the island of Borneo. A key reason for Jakarta’s flooding problem is that the city is one of the fastest sinking cities in the world as a result of the extraction of groundwater, with some parts in the north subsiding by as much as 25 centimeters a year.
A new approach to addressing the floods might hold the key to moving forward. Flood control solutions are expensive, but the cost of inaction is far greater. Jakarta has faced large-scale severe flooding repeatedly over the past three decades, most recently in 2020. The 2007 floods were the worst to date, with inundation in some parts of the capital reaching five meters. Dozens died, thousands were displaced, and the city was paralyzed for days, suffering a damage bill that reached an estimated 5.2 trillion rupiah or US$400 million. And the rate of flooding is occurring more frequently in Jakarta and elsewhere.
Jakarta’s flood warning system makes use of water-level monitoring observed by an Automatic Water Level Recorder (AWLR) at 21 locations. Based on the reading, one of four flood alert statuses will be determined, ranging from “normal” to “dangerous”. The system is effective at regulating the distribution of flood discharge according to a set plan along each segment of the macro system. But flood inundation still happens. Ordinary natural events can turn into disasters. Without adopting localized, specific solutions tailored to the area, the damage will continue and could get worse.
Tailored flood-control solutions in Jakarta have been on the cards since 1973, originally planned for completion in 1985. The completion of Eastern Floodway was delayed almost by a quarter of a century as the government baulked at the enormous, ongoing budgetary support the project demanded. This was as high as five trillion rupiah or US$3.2 billion including the land acquisition.
The solution offered by Netherlands Engineering Consultants (NEDECO) was a sophisticated combination response to flooding that consisted of a macro-system divert of upstream flood water directly into the Java Sea (floodway), and a micro-drainage system of Jakarta, protected by the floodway. The draining system would consist of a gravity system and a polder system. The gravity system is designed for the area where the rainfall excess flows by gravity force into the drainage channel, while the polder system consists of a drainage channel, retention basin and pumphouse. All are specifically designed to account for Jakarta’s terrain, where elevation is lower than the mean sea level.
Big city, big risk
Jakarta has developed into a “megapolitan” city with a population of around 12 million, from a population in the 1940s of just 540,000 residents. There is less than ten percent of green open space left; the rest is built-up and impervious.
The water bodies that were originally swamps turned into areas which were ordained with various names starting with the word “Rawa” (swamp), for example Rawamangun, Rawasari, Rawabelong, Rawabuaya and so forth. Sites of runoff storage have been converted into residential blocks and industrial areas. The drainage system was not properly designed and implemented. They are subject to inundation due to local rainfall and worsen when combined with overflows from the river due to flooding from upstream or high tides which hamper the flow to the sea.
In some locations, this is exacerbated by the occurrence of land subsidence due to uncontrolled groundwater extraction. Flood overflows from rivers generally happen because of silting and narrowing of river channels, which is caused by illegal settlements encamping along the riverbank. These factors all feed into a greatly reduced capacity for Jakarta’s infrastructure to respond when flood-like conditions arise, such as the 2007 flood disaster.
That disaster saw a “perfect-storm” alignment of conditions – days of rainfall in the upper Ciliwung sending flooding to Jakarta, overflows and high tides in the Java Sea that hindered the flow of water to the open. In 2020, extreme rain – between 335mm and 377m of rainfall in one day – was the driving force. In the NEDECO document, daily rainfall of 210mm is projected to be exceeded only once in 100 years. And, at the time, the micro-drainage and polder systems had not been fully completed, preventing the flood-control solution functioning optimally.
The gray and the green
The conventional approach to flood control is to back in hard structures, such as the solutions offered by NEDECO (floodway, drainage channels, polder systems), also known as gray infrastructure. This view assumes that the issue can be managed if the cause of the inundation can be identified. But solely embracing gray infrastructure cannot completely solve a problem as multi-dimensional as flood disasters.
Nature-based solutions – a combination of blue and green infrastructure – could be integrated alongside gray infrastructure to complement or enhance flood-control measures. It cannot replace gray infrastructure. Nature-based solutions utilize water elements, such as retention/detention basins and wetlands, and green elements, like parks, urban forest and green roofs, to build strong environmental resilience against extreme weather.
Non-structural changes have already been made to better protect Jakarta – laws and regulations that regulate matters such as water utilization, conservation and management of water-related disasters. Enforcement of the rules, however, is still very weak.
Standing in the way of successful reform is Indonesia’s rigid, sectoral system of state administration: It is difficult for authorities to access the budget to empower them to focus adequately on solving region-specific issues such as floods.
For example, the Ciliwung-Cisadane River Basin Authority is responsible for managing water resources – including program preparation, implementation of construction, operation and maintenance in the context of conservation and utilization of water resources. The authority also oversees the control of water in all kinds of bodies – rivers, coastal, reservoirs, urban drainage and more. The Authority also has jurisdiction over 13 trans-provincial rivers.
But there are many other parties with a say in Jakarta’s flood problems. Local governments manage drainage micro-systems across the capital, which is not always aligned in the realization of the required infrastructure development budget. The Watershed Forum, an independent group which works with local politicians to coordinate regulation of watersheds, also wants to provide input.
Overarching, unified collaboration among all the major players has yet to happen. The Basin Authority and local Greater Jakarta government struggle to work within the infrastructure development budget, while the Forum does not hold much power since it is a volunteer-based organization that is often more concerned with smaller-scale efforts (planting trees, cleaning up rubbish in rivers etc.).
Collaboration and a unified effort would help mobilize action on Jakarta’s flood problem, but so too would increased spending and a sense of urgency on infrastructure development. The issue is multifaceted and, after decades of lethargy and inaction, time is running short to prevent another disaster in the vein of 2007. The solutions are, it seems, out there – it is now just a matter of implementing them in time to prevent more unnecessary tragedy.