Will North Jakarta Subside below Sea Level?

It is alarming that the level of seawater inundating Jakarta coastal area is getting higher and higher. Today we can notice that at certain spots in Jakarta coastal area the sea water level invading the land could reach up to 2 meters during high tide. Some people think that Jakarta coastal area is in the process of submerging below the sea level. 

Does such a phenomenon really happen in Jakarta? Some surveys conducted in coastal areas indicate that the subsidence of the areas may reach 10 centimeters annually. However, we have to be extremely prudent about such a diagnosis as it may lead us to the wrong solution.

It is true that for some dense populated and industrial areas which are relatively far from the coast,  the high withdrawal rate of the groundwater through the wells drilled in those areas may cause slight land subsidence.

However, this groundwater withdrawal unlikely affects the subsidence in the coastal areas. The evidence of the seawater intrusion up to Central Jakarta proves that such water withdrawal has been compensated by the seawater intrusion to the groundwater formation in those areas. 

There are, indeed, certain spots in the coastal areas which are subsiding, such as on the site of Muara Karang power plant, but all of those subsided areas are ex-coastal land reclamation and cannot be generalized to happen elsewhere. 

Some experts pointed out to the rise of sea water level which is about one centimeter annually. Once again, we have also to be cautious to such claim as the sea water rise should be globally occurring and should be verified whether it occurs elsewhere.

One thing for sure that the sedimentation which raises the riverbed in the estuary of 13 rivers in the Jakarta Bay is the main cause of the sea flood. In the high tide, these shallow estuaries resulting in the mixture of water from the rivers and the sea spill over the surrounding low areas. The original deep estuaries function like "safety valves" which allow the high tide seawater flow deep toward the upstream of the rivers and not spill over the drylands. 

Based on the premise that sea floods coming frontally through the coastline,  the City government is currently planning to construct a high polder along the coastal area preventing for the entry of seawater, locally called rob. The polders will be constructed in two sections of the coastal areas which are vulnerable to sea floods, namely Penjaringan to Kapuk Subdistrict in the west and Marunda to Kelapa Gading in the east.

The initial step is to improve the broken parts of the existing polder and water gates, and by doing so the city government promises that in 2012, North Jakarta will be free from sea flood. The next step is to construct a high polder along Jakarta Bay complete with water gates of 200 meters long to allow ocean liners to make their entry into and go out of Tanjung Priok Port.

Such an ambitious and "luxury" plan definitely will require a huge amount of money. Before the city government goes further with the plan, it is highly advisable to re-scrutinize the diagnosis of the cause of the sea flood in order to get a more proper solution.

We have to consider what some experts said that areas bounded by such high polder will easily become shallow caused by the huge amount of mud and solid wasted discharged by all of those rivers into Jakarta Bay. 

It is highly recommended that the city government spends instead the loan or allocated budget, which is originally destined for the polder construction,  for the periodic dredging of those estuaries and river rehabilitation.  Some of the funds could be also used for relocation of the illegal huts along the river banks and for Jakarta clean rivers campaign. Such spending is definitely much lower than that required for the polder construction.

Pulau Seribu, Thousand Islands in the Sun

As we have a thousand islands for our salad dressing, Jakarta also has a thousand islands but the real ones. Pulau Seribu which is located at Jakarta Bay in the Java Sea literally means "Thousand Islands". However, in reality, it consists only of 128 small islands, but still a large number. Most of these are inhabited and can be reached within one or two hours from Marina Ancol by ferry or by chartered boats. The surrounding reefs are home to a wide variety of fishes, making Pulau Seribu an ideal location for diving, snorkeling, and fishing. The real islands in the sun.

Some of the islands in this group already developed for tourism are Pulau Bidadari, Pulau Ayer, Sepa, Coconut, Pelangi, Bira, Pantara, Kul-kul, and Pulau Putri. There are also cabins for us, from which we can view the golden beaches fringed with coconut palms.

The changes of season and some degree of pollutions are believed to have given a degree of effect to the declining coral reefs of Pulau Seribu, though the surrounding waters are still a paradise for those who are accustomed to diving and snorkeling. The sea water is filled with a myriad of tropical fishes, which live among the multicolored coral reefs. Pulau Putri, Melintang, Petondang, and Papa Theo are among the islands becoming holiday resorts with cottages, restaurants, diving and sailing facilities.

The islands are located at the northern part of Jakarta Bay around 40 to 100 kilometers off the bay. The whole land area of all islands is not more than 860 hectares. Pulau Sebira is the farthest distance from Jakarta Bay, up to 100 kilometers. However, all are easily reached by speed boats available at Marina Ancol.

As the islands are very near to Jakarta which economically powerful, businessmen from Jakarta have converted many of the islands into tourist spots, where marine activities such snorkeling and diving are supported by diving equipment and nice hotel and motel where we can stay.

Degrading Condition

Following its nearness to Jakarta, and highly exploitation of coral reefs and fish catching, the islands’ condition is degrading due to human and natural factors. These factors include the unsustainable technique of fish catching such as bombing, blast, cyanide use, coral mining, and dredging, degrading of water quality due to industrial pollution and solid waste thrown by locals into the sea. The pollution might also contribute to the establishment of various resorts on the islands which involve various activities from project to tourists.

Important Islands to Note
Onrust Island is one of them to mention. Among the cultural preservation, which has a historical value related to the period of Dutch colonial rule in the 17th century, the island was once important boat repairs. Here we can see the relics of the remaining buildings which have been built in a fortress around the 17th century.

We can visit Hope Island to stay overnight in a fine home-stay, which is relatively inexpensive. There are also other islands worthwhile to be visited, namely Angel and Cipir Kelor islands, which become the Heritage Park Archeology of Onrust but, unfortunately, their existence is less a tourist attraction for local residents and foreign tourists respectively.

Princess and Bidadari islands are famous for snorkeling and viewing the underwater aquarium. If you like to lay down in the sand beach, Sepa Island is particularly good for its white sand.

Edam Island, almost forgotten, looks different from the surrounding islands because of its old lighthouse which now is still active. The lighthouse was built at the initiative of the King Willem III in 1879. Five guards and their families occupy the old buildings. We can see the beautiful scenery around the island from the height of  52 meters sweeping the horizon as far as  be 20 miles distance from the island. The building has never been renovated and using exactly the same equipments as it did around 120 years ago.

Apart of this unique lighthouse we can also find the remaining of Dutch fort and a tomb complex apparently belong to the relatives of exiled Banten Sultanate. Sometimes, some visitors come to the island just like to take care for the graves.

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