A Sinking Megacity: What Architecture Can Do To Save Jakarta?
Land subsidence in Jakarta has been one of the most attention-grabbing and critical environmental issues in urban settlements. As in the last two decades, Jakarta has experienced constant land subsidence with an average of 12cm/year, with the highest decline occurring on the north coast of Jakarta with a decline rate of up to 25cm/year. As reported through BBC broadcasts and documentation in 2019, Jakarta will predict to sink in the next ten years, with the National Monument point being 100m from the coastal area in 2050.
According to IFL Science and the Indonesia Ministry of Environment and Forestry in 2020, one of the crucial factors that caused the decline of groundwater levels in Jakarta is the lack of green open space and the massive usage of groundwater. As a result of urbanization, rapid economic growth, and inadequate infrastructure improvements, Jakarta is experiencing the absence of water sources, lack of water services from the piping system, and urban green space decline that causes natural disasters such as flooding. However, several countermeasures for sustainable designs, such as rainwater harvesting, can be a breakthrough solution for clean water conservation and sanitation in Jakarta.
Why rainwater harvesting?
Rainwater harvesting is a collective system method for surface water, such as roofs and channeled into tanks, deep wells (wells, shafts, or boreholes), groundwater, or reservoirs by percolation to seep down and return water to the aquifer layer. By implementing rainwater harvesting methods, water can be used for landscaping irrigation, livestock, and ready-to-drink water with proper care through filtration and densification to meet water consumption quality standards. Given the high rainfall in Jakarta during the rainy season, this method is one of the most highly-efficient solutions for urban settlements that not only supply drinking water but also prevent flooding due to the catchment of overflow run-off water.
One of the interesting case studies with rainwater usage as clean and operational water in buildings is the Roppongi Hills in Tokyo, Japan. Being an experimental city in the heart of Tokyo, Roppongi Hills not only participates in economic development but also adds much-needed green space, thus helping the city from suffering the effects of the Urban Heat Island. The skyscrapers in this area maximize the space available for housing, offices, and entertainment with creative location planners using greenery, a knit complex with a network of walkways, gardens, and green roofs. In comparison to Tokyo's 14% of green open space, Roppongi Hills has 26% percent of its land area planted with vegetation. Meanwhile, the green roof technology of the Keyakizaka complex offers rice fields and vegetables, while the Sakurazaka roof showcases public art and street furniture in a traditional Japanese garden setting. The diversity of landscapes in the Roppongi Hills buildings shows the potential for vertical urban development, increasing green land, and using rainwater to build operational water until ready-to-drink water with the help of disinfection machines and water storage.
Then what about Jakarta?
According to the report by JICA Indonesia in 2020, surface water resources such as rivers and rainwater are the most effective solution for Jakarta, considering the topographical similarities between Tokyo and Jakarta and reflecting on Tokyo's success in stopping the decline in water levels since 1980 within 20 years. However, a rainwater processing system for consumable water has never been implemented in Jakarta due to the chemical compounds and acid rain within the commercial and industrial sectors, which ironically are the highest-demand sector for clean water supply. However, within the innovations of technology and sustainability goals as supporting aspects in new and existing construction for Indonesia's plan in 2040, the filtration and disinfection phase can be calculated and added to the water conservation system for the harvested and processed rainwater.
Some critical aspects considered essential in the rainwater harvesting method are the catchment area of rainwater and the volume of water usage. For the Jakarta area and its surroundings, rainfall is divided into two types, dry and rainy season rainfall. According to data from Badan Pusat Statistik (BPS) Indonesia, the highest average rainfall in the rainy season can succeed almost 25 times higher than the highest rainfall in the dry season. However, due to the high precipitation of rain in the rainy season and Jakarta's geographic location, it's almost inevitable for flooding to happen.
What are other innovations that can be applied?
Thus, to avoid run-off overflow within the ground areas, several applications regarding the rainwater harvesting concept can also be implemented within the landscaping and pavement areas, such as rain gardens and bio-retention systems. A rain garden is a simple bio-infiltration system in a shallow basin or low-lying area, with plants or rock-covered beds specially designed to capture, absorb, and seep rainwater into the soil. Rain gardens are suitable for sites that are sandy, gravel, loam, or mixed with up to 10 percent clay. This method can efficiently remove up to 90% of nutrients and chemicals and up to 80% of sediment from rainwater run-off. Compared to the conventional lawn method, rain gardens allow 30% more water to seep into the soil. In addition, this garden can dry up within 12-48 hours, preventing the breeding of mosquito larvae (Ground Water Foundation, 2021).
Another alternative solution is the Mumbai Ulta Chaata, a rain umbrella method in India created by Thinkphi, a Singapore-based start-up that aims to develop and market sustainable products. Mumbai Ulta Chaata can accommodate rainwater harvesting using an inverted concaved umbrella but also works as a canopy and electric charging, functioning in the parking areas. Through activated carbon filtration, this umbrella filters rainwater below 10 NTU (as per WHO standards for potable water), with a single unit that can harvest up to 1,00,000 liters of water annually. Each Chaata takes up no more than one square foot and provides a catchment area of 360 sq. ft. in return. Additionally, every unit has a wireless RF sensor through IoT to control the solar panel, battery management, lighting systems, water meter, and self-cleaning filters. By allowing more catchment areas, water absorbance can be adjusted to the contrasting figures of rain intensity, both in the rainy and dry seasons.
What are the next steps?
Therefore, implementing water conservation through rainwater harvesting in building designs, landscapes, and cities at a macro level can be a promising solution and a potential answer to the urban settlement issue. Not only creating efficient solutions for the land subsidence and sanitation crisis but also run-off overflow that can cause natural disasters such as floods, providing a sustainable water supply in Jakarta. Through this writing, the author hopes that technological development and innovation can be developed on a larger scale, such as the Drinking Water Treatment Plant (IPAM), adding more water supply throughout the city using water pipes. Thus, clean water not only meets the safety standard and measurements for consumption but can also link the integrated system with IPAM-based treatment of river water sources which are part of the surface water and rainwater cycle. It is hoped that future strategies and technological innovations can also help socio-economic growth regarding clean water and sanitation, such as plumbing problems and high water bills, reducing flood victims and improving the welfare of urban people's lives.
DAFTAR PUSTAKA
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Daftar Pustaka dari Situs Internet (web site):
BBC. Extreme weather: What causes flash flooding? https://www.bbc.com/news/science-environment-57969877.
Data Curah Air Hujan DKI Jakarta, diperoleh dari Badan Pusat Statistik DKI Jakarta melalui situs internet, https://statistik.jakarta.go.id/iklim-dan-cuaca-dki-jakarta-tahun-2020/.
Data Energi Dan Air Bersih DKI Jakarta, diperoleh dari Badan Pusat Statistik DKI Jakarta melalui situs internet, https://statistik.jakarta.go.id/energi-dan-air-bersih-dki-jakarta/.
Data Jumlah Pelanggan Air Bersih DKI Jakarta, diperoleh dari Badan Pusat Statistik DKI Jakarta melalui situs internet, https://statistik.jakarta.go.id/jumlah-pelanggan-air-bersih-di-dki-jakarta/.
Data Perbandingan Kota Jakarta Dan Kota Tokyo, diperoleh dari Compare Cities, http://comparecities.org/en/compare/Tokyo-Jakarta.
Data Statistik Wilayah Jakarta Barat, diperoleh dari Badan Pusat Statistik DKI Jakarta melalui situs internet, https://statistik.jakarta.go.id/jakarta-barat
Groundwater Foundation. What Is A Rain Garden? https://www.groundwater.org/action/home/raingardens.html
IFL Science. Sinking Ground Could Affect 19 Percent Of Earth's Population By 2040. https://www.iflscience.com/environment/sinking-ground-could-affect-19-percent-of-earths-population-by-2040/.
Smart Cities Council. This Inverted Canopy Recycles Water. https://www.smartcitiescouncil.com/article/inverted-canopy-recycles-water-then-generates-solar-energy-too.
World Research Institute. Three Cities Taking Urban Forestry to the Next Level. https://www.wri.org/insights/3-cities-taking-urban-forestry-next-level.
