Jakarta under constant threat of flooding and rising sea levels

Sukristiono Sukardjo Jakarta Post 23 Jan 13;

Jakarta, with its booming population, is facing a challenge from anthropogenic climate change. The city represents an exceptional concentration of 10 million people located close to the sea’s edge and therefore vulnerable to rising sea levels.

Greater Jakarta is a delta city that has constantly been at risk of flooding. During the Indonesia Delta Forum held in Semarang in October 2010, the unabated flood problems beleaguering Jakarta were discussed, and 13 rivers running from Mount Gede, Mt. Pangrango and Mt. Salak in West Java were identified as permanent threats to the capital city.

The quality of all river catchment areas has been degraded due to disposal of solid and domestic waste, continuing illegal development activities and other environmental encroachments have complicated rising sea level mitigation and adaptation efforts.

Jakarta, West Java and Banten mangrove forests occupied 44,453 hectares in 1996-1998, accounting for 0.66 percent of Java’s north coast. In 2009 the forest cover had declined to only 11,370 hectares.

These mangroves support Jakarta bay fisheries, provide coastal protection against typhoons and storms, reduce erosion, stabilize sediments, control flooding and pollution, and serve as habitats for many forms of biota.

Jakarta’s mangroves grow in narrow, discontinuous strips along the seaward face of the stretch from Kapuk Naga to Muara Angke and help Jakarta withstand the tides. Kapuk Naga mangroves, however, have been vastly diminished, while the 25 hectares of mangrove forest in Muara Angke sanctuary are coming under attack from pollutants.

Nature reserves in Penyaliran Barat (18.41 hectares) and Penyaliran Timur (19.50 hectares) as well as fishponds cannot recover despite rehabilitation activities. The Jakarta mangroves have been degraded environmentally and structurally, their natural water regime has been disturbed, rendering them unable to protect the coasts from rising tidal floods.

Meanwhile, forested areas in Mt. Salak, Mt. Gede and Mt. Pangrango and 13 catchment areas are environmentally degrading at an alarming rate as a result of development and other human encroachments. The upland areas are the target of developers hungry for land.

Uncontrolled development of upland regions and the growing wealth of Jakarta’s citizens lead to new high quality residential areas at the expense of small lakes, putting the city under permanent risk of flooding.

The 1993 Kapuk Naga reclamation program, along 30 kilometers of coastline, affects some 4,000 hectares of seashore. This reclamation will fundamentally change the contours of the coastal zones in Jakarta bay and the gradual interface between land and water will be replaced by an abrupt separation of land from the marine environment.

The choice to change the use of shallow coastal zones and build new residential areas to meet demand from the growing population will bring new catastrophes in its tide.

It is now only a matter of time before mangroves are totally erased from the map of Jakarta — a victim of unbridled urbanization and industrialization programs initiated by the government, which, in the same breath, pronounces its concern about Jakarta’s ecological balance. Mangrove forest loss will certainly lead Jakarta to total flooding from tides and from upland, which will rank among the most devastating natural disasters in the contemporary history of the city.

A number of field surveys and scientific studies show a decline in tree density in the three mountains south of Jakarta, reducing their capability to mitigate water runoff during heavy rain. These trees need to be managed for survival and growth as flood mitigation elements against climate change.

Hydrological regimes are justified on the basis of claims that the dense trees of mountain forests have provided protection against flood. Increasing tree density will enhance the mitigation effects of mountain forests. To mitigate the impact of climate change mountain forests, catchment areas and mangroves in the northern Java coastline are important and must be protected for their multifunctions.

In 1923, the mangroves encircling parts of a 50 kilometer-long area along the then Batavia coastline, extending between 2 and 7 kilometers inland, especially from Muara Aluran and Muara Angke, mitigated tidal floods. The amount of mitigation was documented in historical records, but it may soon be reduced to a mere memory.

Tree-planting campaigns to rehabilitate catchment areas and reforest cleared mountain areas are the keys in mitigating flood impact. Attempts to bridge a gap between science and policy can materialize by presenting and synthesizing information on catchment area and forest protection drawn from empirical studies, simulations and mathematical models.

I personally suggest that 13 catchment and coastal areas be rehabilitated as soon as possible. Squatters along the catchment areas in Jakarta, West Java and Banten should also be properly educated to ensure conservation and eco-friendly environments. The 13 rivers with sediment-garbage loads and tree-felling are examples of human egoism.

Not only do floods damage the infrastructure, but also cause humanitarian problems. Jakarta is at risk of global warming, rising sea levels and climate change, therefore it needs mountain forests, mangroves and associated healthy rivers to provide natural protection from hazards. Mountain forests and mangroves, however, are a source of conflict among Jakarta, West Java and Banten. The point is Jakarta needs well stocked upland forests, mangrove belts, urban forest renewal and improvement to 13 catchment areas and the coastal environment to anticipate floods and climate change.

Many environmentalists, ecologists, moralists and sociologists recount how Jakarta’s rapid increase in population gives rise to a demand for housing, living space and other human necessities, without paying attention to social ethics. Jakarta floods can be regarded as a moral issue. Too many talk about the flooding, but are Jakarta, West Java and Banten government officials, councilors and development planners listening to the voices speaking up for the diminishing upland forests, mangroves and 13 unhealthy rivers?

The writer is a professor of mangrove ecology with the Research Center for Oceanography at the Indonesian Institute of Sciences (LIPI).