Dot dot bobolnya Bandung Lake

In this daily, several times published articles about the breakdown of Bandung Purba Lake written by T. Bachtiar. The writings were based primarily on the scientific paper in Geological Magazine Indonesia Vol. 17 No. December 3, 2002, issue of Indonesian Geologists Association (IAGI), entitled “Analysis of Geomorphology Hills Saguling-Sangiangtikoro: Drying Bandung Purba Lake Caves Sangiangtikoro not Through” by Budi Brahmantyo, Sampurno, and Bandono.

On paper it is proved that the cave Sangiangtikoro the elevation of not more than 354 m above mean sea not the cause of the breakdown of Bandung Purba Lake. Capricorn Caves in Sangiangtikoro are high natural wall and sturdiness that a barrier puddle with Sangiangtikoro ancient lake. So that the ancient lake receded, must be breaking this barrier wall that connects the tops punggungannya namely Pasir Kiara 732 m and 850 m Peak bans.

How extraordinary mechanism that can break into the hard wall of rock breccias this? The answer is a process of erosion upstream! When a small river that flows in the north slope of the wall is spread out valleys eroded towards the upper slopes of the barrier wall, until one day he jumped the crest of the ridge and see ancient lake shore, that’s where the drying process takes place.

Calm lake water was stagnant, find a way out through innovations that extend the small river valley upstream of it. Lake water started crashing the small valley and the longer the grind and cut, widen and deepen the small valley. Finally, when the process takes place continuously incising valley, creating a large valley with a strong flow and … Bandung Purba Lake also find a way to drain water into the sea.

Valleys that new stream segments that drain Citarum ancient lake of about Saguling now to meet again with the first stream in Cimeta which now empties into Cirata. The segment includes a narrow valley known as Cukang Rahong and waterfall waterfall Mist. Among the natural landmarks of this, evidence of burglary Citarum can be recognized, especially in geomorphologically.

Notches point Citarum

Before Citarum Saguling dammed in 1986, the flow of the river in this segment is remarkable. You can imagine the whole flow of the Citarum water flows in a narrow rocky valley, creating rapids and waterfalls, terraced between Cukang Rahong and Curug Hazy. This stream flanked by steep slopes 60-70 degrees both on the slopes Pasir Kiara in the east, as well as highlight bans west.

Once dammed, most of the Citarum water diverted through a tunnel and two rapid pipes to turn turbines near Sangiangtikoro. After this round of water energy generating 700 MW of electricity, the water is then returned to the original channel Citarum in Sangiangtikoro. As a result, the segment of the river between the dam dries up Sangiangtioro and supplied only by small rivers, including by Cicacaban and Cikondang.

Down a small watering segments, especially between Cukang Rahong and Waterfall Mist, an exciting exploration of the riverbed. For me a geologist, stones that had been submerged in river water and is now exposed to the surface, into the new data in the geological treasures in the region. The layers of volcanic breccia, the rock rough lumpy compact bonded into a massive, alternating with sandstone, the layers are clearly visible, showing how the rock structure is a barrier that is perfect for a pool of the ancient lake.

A Cukang which means bamboo bridge, antiquity never crossed a narrow valley, but the valley Rahong, so it became known as Cukang Rahong. The bridge is a vital link between the traditional transport Cililin Ciranjang Bandung to Cianjur. The bridge hung over the valley as high as approximately 40 m from the valley floor has a width of 7-8 m only. Narrow valley with a length of no more than 25-30 m flanked by vertical walls of rock breccia hard.

Another phenomenon that is no less interesting is plenty met Potholes, the pot-like holes in the rock. These holes are created in the riverbed when it was originally a small indentation crushed spun by sand and gravel that are increasingly in. No wonder if we could achieve bottom of the hole, we will encounter a lot of sand and gravel. Several holes have a depth of more than two meters, with a diameter of 1-2 m Similarly, although many are small and shallow.

Additionally, waterfalls and rapids stratified adorn the Citarum segment loss of this magnitude flow. Before reaching the largest waterfall in the river segment is Curug Hazy, from upstream we will encounter several small waterfalls.

Hawu waterfall with a height of 3-5 m is the first high rafting river where the water falls on the slopes straight from the layers of rock breccia. If the easy achievement of a crowd, surely the waterfall would be a tourist attraction. Besides not too dangerous, the pool created under it provides a water play can be fun.

Similarly, the next waterfall is Curug Pangulaan formed from the same rock types. Height 5-6 m, so here we need to be extra careful to pass it. One slip, we will fall sliding over the sloping surface is hard, rough and sharp.

Downstream, near Curug Hazy, encountered several rapids again. Rapids is actually more of a barrier streams by giant blocks of stone. Locals do not give names to the rapids, so we call it just by the waterfall cascade occurs prevented Batubuleud for large rounded rocks and waterfall bayawak because it encountered a large lizard sunning.

Large blocks of stone that blocks the flow of this seemed to be falling from the upper slopes. Everything is as if caused by a major disaster. These large chunks of the more closer to the waterfall Mist. Well, this is most likely physical evidence or point their nickpoint notch.

Nock point is a point on the gradient of the river if we make a cross section along its flow longtudinal. Normal river that has flowed old with eroded rocks will provide essentially proportional curve curved cross-section without interruption. But the river is broken up flow or due to new influences from other river, the river gradient curved cross-section as if broken or tertakik.

Nock point is generally attributed to changes in river flow as a result of basic rejuvenation process flow. At this point that geologically there is something that affects the flow, can be a result of the fracture, break rocks from below, or hijacking other river flow by.

If we make a cross section of the gradient of the river from the bridge Citarum in Rajamanadala until Saguling, we will be able to curve it tertakik around Curug Mist. Obviously, like many written textbooks Geomorphology, a waterfall is one proof point of this notch.

Curug Halimunlah, evidence points Bandung Purba Lake notches piercing through piracy erodes the river flow upstream on the barrier wall Pasir Kiara – Disallow peak, is clearly visible. Curug Hazy free fall almost as tall as 10-15 m in rock breccias, suggesting this is where the bulk drain spilled water Citarum Bandung Purba Lake.

After heavy riverbed between Cukang Rahong crawled up to the waterfall Mist because of the many rapids and large chunks, the river flow downstream after Curug Hazy up to Sangiangtikoro, has a valley that is not “as bad as” flow on it.

Indeed, a segment Cukang Rahong – Hazy in the Citarum waterfall which dries because they Saguling, a wealth of natural heritage and earth Bandung Basin is unequaled. Fortunately achievement to this location it is not easy because they have down the steep slope of 60-80 degrees and a depth of up to 80-100 m (imagine the return should rise seterjal and that high anyway), so that this heritage can secure a beautiful and slightly susceptible to interference from people who do not care about natural resources ***

By: John Brahmantyo; lecturers Engineering Geology, Applied Geology KK, FITB, ITB, and members of the Bandung Basin Research Group.

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