Hot mudflow in Siring Village, Sidoarjo since May 29, 2006 had an large impact . More than 2.500 people were evacuated, ten factories closed and paralyzed the highway. One big question is how much the volume of the hot mud. BAKOSURTANAL joint team,ITS and the ITB has to calculate the volume by using the Geographical Information System (GIS).
Field surveys conducted by measuring the height mud at 12 points in the source and the outer side. High from the source measured from the mud distance of about 10 meters, was height calculated from the outer side ,difference between the mud and the fields surrounding which not flooded.
And the Results Mudflow dimensions: - Area: 110.84 hectares
- Round: 6523 meters
- Volume: 1.12 million m3
- Debit: 50,785 m3/day
Until now, the content of the mud flow has reached the security embankment over 6 million m3, the volume of spray per day had reached 126,000 m3, area has reached 400 ha, and until the end of September 2006 has occurred at least 9 times of mud from crack dike safety. Reaching submerged villages 8 villages, namely: Siring, Kedungbendo, Jatirejo, Renokenongo, Pajarakan, Mindi, Besuki and Kedungcangkring. Altogether has been declared by the Sidoarjo regency administration is not suitable for habitation. If viewed periodically, from time to time, the condition of the Sidoarjo hotmud expanding and increasingly out of control. The question now is how long this situation will continue. It is difficult to guess, from the blowout to the phenomenon of underground mud volcano and now a disaster-prone areas, there is no mud management actions and decision on the disaster zone. With the establishment of a disaster-prone areas is by itself the area around the blast was the region that must be evacuated, including relief activities well, and before discharging to attempt settlement of hot mud and security.Porong village hot mud are mobile, because almost 70% water and only 30% is solid, so the estimates will form a conical mountain of mud nearly impossible. Activities to be done is to spray the area management and management of mud / muddy water that continued to build in order to give added value to society and the environment. Content of hot mud in the district. Porong, Sidoarjo has been an alarming stage. From day to day in the mud volume in the reservoir embankment continued to grow and levee conditions also did not hold more mud pressure, because the levees were designed in an emergency, and for a while. But what happens when this is not a decision about the management and placement efforts are permanent mud, although the government has set local Porong Lumpur Lapindo, Sidoarjo as disaster-prone areas (Potential Hazard Area. In addition, until this moment the suffering people of Sidoarjo becoming less ends, living in tents evacuation suffered physically and spiritually, until when?. This is a fundamental question shared responsibility. If not, then the endless suffering Porong and surrounding communities are never has a solution. But it was clear, human life is far more important than fish life in the Madura Strait. The view of experts from government agencies and related professional organizations, are often disclosed in various forums. Even the various institutions and professional organizations have done various analyze, and modeling studies independently of Porong mud. Some conclusions about the mud Porong mud and muddy water is not dangerous, because the results of laboratory analysis showed that the elements in the mud and muddy water under the government established quality. As announced by the Government decree on 27 September 2006, the Porong Sidoarjo declared as disaster-prone regions. If current conditions are as disaster-prone areas, the Porong and surrounding areas as well as the area is inhabited or not worthy to be a place to stay and live. Porong Society since declared as disaster-prone areas are should forget their villages and homes, and for the relocation of residents at this time also must be done. If the Porong has become a disaster-prone areas, then of course the area should be empty of human activity, because any time a disaster that could destroy and kill is can happen really . The task now is to control the region to disaster and disaster impacts are not widespread. two choices, namely: (1) management and control of Porong mud to overflow and flow control to the permanent location and (2) relocation of communities around the blast to appropriate place and secure.
But if the choice is to let the mud Porong out naturally, builds up and flows, the current population at around bursts must be moved immediately and look for shelter locations and permanent life as well. Why is that, because the blast had happened already regarded as a natural phenomenon that may take longer. In addition, the area around the blast of the community residence for the days ahead no longer meet the statement to be a place to stay. Stated or not, the fact is that the area around the blast has become a disaster area. Disaster actually happens is home, infrastructure and agricultural land have been covered with mud and future "environmental recovery more difficult, let alone" social recovery "takes a long time on physical condition and surrounding Porong Area. Porong Regional topography and morphology of the Madura Strait and the topography of the area surrounding Porong is the watery swamp areas throughout the year. These regions included in the lowland areas of East Java, North Section. Ground level is almost the same as the sea level with an average elevation difference 1 - 1.5 m, so that when the tide comes, the river and pond rising participate. The topography of the sloping beach and even lower than the high-water mark, causing the movement of river at a slower pairs tend to move even fill land area , rice fields and agriculture.
The slow motion is caused by the difference of elevation between the marsh plain surface and morphology of coastal waters is almost the same, making it easier to push back the tide of material into the ground. Even at the highest tide (slack maximum), sea water moves landward up to the foothills area (backshore), then branching into the river and will enter the population ponds that surround the branching river.
Current conditions shows that, the flow of mud around the blast area to move in any direction because the topography is almost flat. Porong local topography, which is low land would result in the flow of mud into the rivers and ponds to move more slowly. But because the numbers are large, the movement to the side when the embankment collapse will be greater.
Movement to the sea will take a long time, so it is with the placement using a pipe requires greater pressure to the mud can move more quickly in line with the increased volume in the reservoir dam burst around the seabed morphology of the Madura Strait can describe the condition of the valley that lies beneath the surface of the depth of 20 to 60 meters. The valley extends from west to east, and deepening to the east up to the Bali Basin, the Valley is as if describing the direction of sedimentation beneath the surface and the liquid flow below the surface to the west - east. Movement can be seen also from the movement of sediment from the Surabaya (narrow line) to the east up to the middle of the Madura Strait. Bathymetry is important to get the condition and lumpu catchment. Naturally (naturally), the mud will settle to the valley areas with little energy, even without the current. Symptoms of decline Land Surface Area around the mud flow was showing symptoms of decline in a circular motion to form a normal fault pattern. two possible causes of the decline in surface soil, namely: the pressure due to accumulation of mud on the surface around the center of the blast and the void below the surface due to continued running out hot mud from the surface of the soil condition is different from the Bluduk Kuwu Purwodadi and mud volcano in the Kalang Anyar (South Airport Juanda, Surabaya) not a lot of mud, but only the gas, so that no congestion occurs on the surface and subsurface vacancies.Decrease in soil surface condition is very dangerous for the infra-structure and building . Therefore, in addition to the dangerous houses when occupied, the infrastructure is also dangerous to remain employed, the infrastructure also needs to be moved into the stable area dangerous to infrastructure and building houses . Sedimentation Lumpur on Madura Strait Based on Generally Seismic Data under the surface sediment in the waters of Madura Strait obtained from seismic reflection data with data correlated to obtain sediment vertical seismic drilling interpretation results of the path north - south of Madura Strait cut the results correlated with data showing core drilling sludge (clay ) which is the sequence of the sea surface reaches a thickness of 15 to 25 feet of gray to black. The results of these seismic recordings to illustrate the process of sedimentation and sediment layer surface patterns. These results also show that the mud on the seabed has grown more Madura Strait (progradation sediment), whereas the more material into the more subtle. The lower part shows the pattern of seismic reflectors are different, this shows further down the more coarse material. Based on the character of the precipitation test between the mud and the mud Porong Madura Strait in seawater media, the more mud Porong quickly to the bottom of the sea, and at the Madura Strait mud reached the bottom of the sea will cover the mud Porong.
Results Porong mud sedimentation test four types of media in water (sea water Madura Strait, the water Porong river. Porong river estuary water and mud water / seepage) shows the characteristics of orientation (time) deposition of different, although there are conditions that sedimentation rate same as the basic approach.
Precipitation is expected to test at least gives a picture of the characters in the media mud in the water without the interference conditions, and with the same treatment. In the first 5 minutes of first mud moving down to the water of Porong river, on the estuary mud water began to descend, while the media Madura Strait sea water and mud water / seepage precipitation has not occurred. In the tenth minute, the mud has been moving in all the media, and the movement of mud on the water of Porong river fixed more quickly, while the water estuaries and almost the same muddy water and the sea water more slowly. But after 40 minutes and then showed a tendency to the same sedimentation rate and the slowing and turbidity at the top disappeared. Deceleration is caused by the material of mud have started approaching the bottom, so that was blocked by the mud that settles first, but when the sea water with a depth of field is bigger, then after 40 minutes was surely going to move as a tendency in the early minutes to 20 minutes , because in the early minutes to 20 minutes showed decreased velocity of rhythm.
This result at least gives an overview that gives Porong mud trend moving toward the bottom and it also proves that the weight of is greater than the media of all types of water tested.
To compare the trends and characteristics used mud deposition taken in the midst of the waters of Madura Strait. Five taken mud samples at five different locations. These five examples are all tested on seawater media. Sedimentation test results showed a tendency to move more slowly settling of mud. In the first hour, the precipitation process is still going on and turbidity in surface water along the decline has not disappeared, but the kind of black mud settles faster than the mud-yellow type. Sedimentation and turbidity completely disappeared after five hours.
Of the two types of mud (mud and mud Porong Madura Strait) is deposited in various seawater media showed that Porong mud settles much faster in all water media compared to the Madura Strait mud. Although the test Porong mud sedimentation in the sea water, slower than in waterof Porong river, water estuaries Porong mud and water / seepage, but the overall difference was not significant, even when compared with the settling of the Madura Strait mud, mud sedimentation Porong much faster.
All the liquid and solid in nature will be moved to follow the direction of motion of gravity, which is leading to a lower area. Mud and muddy water as part of the solid and liquid are naturally a time to slide and move into the lowest areas, namely: the hollow in the sea. No exception with a solid object (rock), will experience weathering, erosion and transportation. Where then will the end of the movement, the answer is to the hollow in the bottom of the lake or the ocean floor. If the basin of the lake, eventually also to the bottom of the sea by rivers which flow out of the lake. While at the bottom of the river will be sediment, a time when the volume of river water due to high rainfall will tertransport to the seabed.
Porong hot mud is an easy type of object moving and mobile, because almost 70% water and 30% are solids, so the estimates will form a conical mountain of mud take a long time. If the mud to reach the shore (nearshore) the dominant factors that will affect the flow of mud that is parallel to the shore (longshore current) and the wave broke (breaker zone). As a result of mud will move in any direction horizontally; part to the coast and partly into the sea. On the beach will form new beaches and delta young (recent deltaic). At sea (offshore), the mud will settle to the area with waves and currents are weak (low energy). Low-energy region in the sea can be determined by oceanographic measurements, even from the indicators of sediment deposited in the sea, can be determined mud deposition area.
Regional mapping of low energy spread of the Basic Sea Surface Sediments with grain size method of Folk (1980) characterized by the type of fine-grained sediment (clay). When placed in Sidoarjo mud sediment area clay, it means there is a process resedimetation hystory, it means repeating the previous mud sedimentation process. This process also occurs in the nearshore areas, sediment will occur in low-energy region, except at the shoreline and the wave strikes the influence of longshore current is strong enough and will be distributed in the mud along the shoreline at a considerable distance.
Low-energy region is characterized by the spread of clay (clay zone), generally has a sloping seabed morphology and almost flat. In the deeper sea, sloping morphology is formed between two cliffs or in the middle of the valley, and the rivers emptying into the sea to the valley. In the waters of Madura Strait, the low energy and clay sediments located in the middle of the strait of about 3 to 5 km from Delta Brantas with depth contours between 40 to 60 meters.
If the mud already entered the area with waves and strong currents so naturally it will move the mud to find areas with wave and current conditions are weak, but can be after going through a wide area, moving floating irregular, meaning that spread in many directions in floating, before it settles. Water color blue original color will change following the mud. When the color of black mud like color Porong mud, the sea water would be black too.
Dangerous natural phenomenon of sedimentation of mud in the sea is in the event of changes in regional oceanographic patterns, such as wind, wave and tidal currents with a larger scale than usual. Such phenomenon may occur due to the annual cycle, five-year and so on. However, changes to precipitation patterns and shapes mud seabed morphology is not too significant, because it only occurs on the surface. Changes will only look at the shoreline when the phenomenon lasted longer, the mud that has settled will be swept away by huge waves lunge toward the more distant and difficult to control.
This condition can worry about changes in nearshore ecosystems extensively, because in many coastal waters contain the mud will be changes in salinity, conductivity, temperature, oxygen and other dissolved substances.
Environmental Brantas Delta Estuary is a typical delta environment (Estuary), which is the area between transition terrestrial environment (river) and the sea. Brantas Delta Estuary is located approximately 15 to 18 km from the location Lumpur Lapindo, this area is also known as the shallow sea waters (nearshore) to form Brantas delta. The characteristics of this region is moving parallel to shore flow from west to east direction, wave height ranging from 0.5 to 2 meters, the beach is usually a lumpuran sediments and mangroves, some made fishpond land. Tidal currents and waves coming from the northeast looking from the form of the Brantas River estuary from south to north a little to the northwest turn.
As you can see here for further view ,imagine how big disaster it could bring to this area.
Action that should take or possible corrective action:
1. kill the natural venting by drilling relieve well and disposed cement in
Kalibeng zone (or deeper zone depending on the result of damage zone
investigation)
2. control surface venting by drilling & producing the mud close to the
natural venting area (5 spots?), or
3. abandon all the area flooded by mud & make them natural museum (the mud
venting may continue on months or years until the pressure stabilizes)
