**5. Discussion**

inundation. **Figure 13** shows a graph of the subsidence in the Demak area along with a picture of tidal inundation in the field, as well as a depiction from a time series of high-

**Figure 13.** Graph of land subsidence in Demak (modified from [8]) correlated with pictures of existing tidal inundation and also with satellite images of land sinking (sources: authors, [18, 19]). We can see the general linear trend of subsidence

Pondok Bali Blanakan is a coastal area a few hundred kilometers east of Jakarta, and is mostly a farming and fishing area. First, it is quite surprising that this natural farming and fishing area is suffering from significant land subsidence. Nevertheless, after a detailed investigation we found that the area is an oil and gas exploitation area. The huge amount of oil and gas exploitation is causing subsidence. While the low land of the coastal area is sinking over time, more frequent tidal inundation is attacking the area and in certain places it has already become permanently inundated. Based on high-resolution satellite image analysis, it was found that a few hundred hectares of the Pondok Bali Blanakan area are suffering from inundation. **Figure 14** shows a graph of the subsidence in the area along with a picture of tidal inundation in the field, as well as a depiction from time series of high-resolution satellite

image analysis. Again, we can see clear evidence of disaster.

resolution satellite image.

indicating the sinking of the land.

52 Natural Hazards - Risk Assessment and Vulnerability Reduction

Based on the correlation between land subsidence and flooding in some areas in Indonesia we can see clearly that the correlation between them is very strong and may result in disastrous situations. We can see that the significant area suffering from subsidence is also constantly suffering from flooding and tidal inundation. When we speak of disaster, we tend to think of economic loss. Indeed, millions of dollars have to be spent fixing problems from both land subsidence and flooding, and it seems more will be spent in the future. So, based on this fact we need better mitigation and/or adaptation. For example, if indeed flooding proves to be influenced significantly by land subsidence, in this case reducing or even stopping the subsidence might be the best mitigation. This fact shows that it is possible to stop land subsidence by stopping groundwater extraction and/or recharging artificially [8–10, 14, 20].

As far as we have seen, mitigation and/or adaptation are still beyond the best agenda in Indonesia. Only sporadic or short-term measures have been created against these problems such as building temporary dykes, elevating the land, roads, housing, etc., including building up mangrove areas in many places along coastal subsiding areas. Long-term measures such as building giant sea walls or stopping subsidence are still ongoing or are being planned and discussed. In fact, talking about stopping land subsidence is still an issue. Note that sometime in the future these problems may worsen if we see significant linear rate of subsidence in those areas; on the other hand, attempts to mitigate or adapt to this situation are still beyond the best agenda.

once again that in the future these disastrous situations may even worsen if we see a significant linear rate of subsidence. This chapter will hopefully become a lesson learnt for other places around the world, especially those growing countries prone to subsidence and flooding.

Insight into the Correlation between Land Subsidence and the Floods in Regions of Indonesia

http://dx.doi.org/10.5772/intechopen.80263

55

Many thanks and appreciation are given to Badan Informasi Geospatial, Ministry of Public Work, and Dinas Perindustrian and Energi Jakarta for sharing the program of monitoring land subsidence in Indonesian regions. Appreciation is also given to students from the Institute of Technology Bandung who helped with investigation in the field, and Deltares Research

Heri Andreas\*, Hasanuddin Z. Abidin, Irwan Gumilar, Teguh P. Sidiq, Dina A. Sarsito and

[1] Bell J, Amelung F, Ramelli A, Blewitt G. Land subsidence in Las Vegas, Nevada, 1935-2000: New geodetic data show evolution, revised spatial patterns, and reduced rates. Environ-

[2] Abidin HZ, Djaja R, Andreas H, Gamal M, Hirose K, Maruyama. Capabilities and constraints of geodetic techniques for monitoring land subsidence in the urban areas of

[3] Abidin HZ. Suitability of levelling, GPS and INSAR for monitoring land subsidence in

[4] Abidin HZ, Andreas H, Djaja R, Darmawa D, Gamal M. Land subsidence characteristics of Jakarta between 1997 and 2005, as estimated using GPS surveys. In: GPS Solutions.

[5] Abidin HZ, Andreas H, Gamal M, IGumilar I, Napitupulu M, Fukuda Y, et al. Land subsidence characteristics of the Jakarta Basin (Indonesia) and its relation with groundwater extraction and sea level rise. In: Taniguchi M, Holman IP, editors. Groundwater Response to Changing Climate, IAH Selected Papers on Hydrogeology, Chapter 10. Vol.

Geodesy Research Division, Faculty of Earth Science and Technology, Institute of

Institute, which provided recent knowledge on flooding and modeling.

\*Address all correspondence to: heriandreas49@gmail.com

mental and Engineering Geoscience. 2002;**8**(3):155-174

Indonesia. Geomatics Research Australia. 2004;**81**:45-58

urban areas of Indonesia. GIM International. 2005;**19**(7):12-15

Berlin/Heidelberg: Springer; 2008. DOI: 10.1007/s10291-007-0061-0

16. London: CRC Press; 2010. pp. 113-130. ISBN: 978-0-415-54493-1

Technology Bandung, Bandung, West Java, Indonesia

**Acknowledgements**

**Author details**

Dhota Pradipta

**References**

Indonesia is one of the fastest-growing countries in the world. In spite of this remarkable achievement, the ecological potential disaster from subsidence and flooding as explained in this chapter is quite serious. It is perhaps one of the mistake actions on growing the country. This descriptive chapter can be a lesson to learn for other growing countries. Do not make the same mistake. Do not let subsidence happen significantly. If possible do not let it happen at all. Singapore is a prime example for less subsidence. This country forbids the extraction of any groundwater.

We have been warned of global climate change consequences. Melting of ice caused by rising global temperatures is making the sea level rise. This sea level rise is projected to cause risk of flooding in coastal areas of the world. By this descriptive chapter we can see the risk is even multiple higher. The rates of sea level rise are generally a few millimeters per year [21, 22], while coastal subsidence can be up to a decimeter per year. This means that global climate change consequences may arrive earlier for coastal-subsiding areas such as Jakarta, Semarang, and probably others in the world.
