Flood resilience within the Garang Watershed in Central Java has at the least involved two main regions which are Semarang Regency and Semarang City. Semarang Regency, which is located in the upstream area, is ecologically important in terms of flood management that could affect the mid- and downstream area. Therefore, it is important to maintain the quality of the ecosystem and its services that contribute to flood prevention such as the storm water management.
As population is growing in both the city and regency, the need for housing has also increased along with development. This expansion has certainly caused land use changes, for example from rice cultivation into real estate for building, which affects the availability of areas for water catchment. Suroso from Semarang State University (UNNES) said that ideally a watershed should have 30% of its space as a water catchment area. However based on a recent study, it’s still only 22% out of the target and it is quite a task to improve this percentage and not the other way around. This is especially so with the rapid development happening in the area. It is evident that the east part of Semarang Regency, which is part of Garang Watershed, has mostly been covered with residential land use. While the western part of the regency is still relatively green, it also suffers from inappropriate farming practices that cause even more flood and erosion.
Mercy Corps Indonesia (MCI) has had the opportunity to implement a flood risk reduction effort in Garang Watershed through the TRANSFORM program funded by Global Resilience Partnership (GRP) – Water Window Challenge supported by Z Zurich Foundation. MCI decided to take action to prevent further hazardous activities by focusing interventions in the regency because it is the upstream area of the watershed. Besides providing the farmers and village officials with knowledge, the team also tried to engage private stakeholders who are significant in terms of real estate development.
EcoMetrix Solutions Group (ESG), as a MCI project partner, has performed a cost-benefit analysis that was looking to uncover how land use change will impact the flood risk in the future. It is understood that land conversion of 1 hectare of rice paddy field into residential area in the regency will quadruple the amount of runoff at that site. The results of the study indicate that, if left unchecked, there will be an ongoing increase in runoff as a result of continued urbanization. In fact, if the rate of land use conversion from rice paddies to residential area were to continue into the future at a rate of 15%, then by 2031, the upper Garang River basin would be sending an additional 393 million liters of stormwater downstream during peak flow periods. Therefore, it is very important to influence some change in how residential area is developed along the watershed.
Together with other relevant government bodies, the team has conducted intensive dialogues with one of the biggest housing project developers in the regency (name withheld for privacy). The area on which the housing was built was supposed to be a rice field that also functioned as a catchment area. The development of new housing, especially without proper storm water management, is believed to have caused unprecedented flooding in the neighborhood. However, since development is inevitable, stakeholders should find a way to maintain the ecosystem function despite the land use change. Along with advocacy work to housing developers, MCI has also been putting their effort into influencing better a monitoring mechanism from the government side, including the land use planning.
As part of the cost-benefit analysis that mainly relied on Ecosystem Services Identification & Inventory (ESII) Tool, ESG and MCI also brought intervention options in order to retain ecosystem benefits. These storm water management options were then selected by local stakeholders within the Garang Watershed Transboundary Forum based on their considerations of impact and replicability. Tree planting, swale, and dry wells are the three flood risk reduction interventions that are implemented with expectations to be scaled up through different opportunities. One of the areas being observed was Kalirejo Village, where a big housing project is being developed. The land profile of the housing development site is considered suitable and in need of dry wells and swale construction.
The Environmental Agency at the regency level, as the main partner of the program, plays an important role in this strategy as they have the authority to conduct environmental impact assessments and generating recommendations for real estate permits. According to the agency, most of the housing projects in Semarang Regency were required to have an environmental management plan and apply it in their construction. However due to the lack of resources, it is difficult for them to carry out the supervision, monitoring, and evaluation, thus resulting in most housing developers not complying with the aforementioned requirement.
That is why, according to Budi Santosa, the head of Environmental Quality Improvement division of the Environmental Agency, participation from NGOs and the community is really vital particularly for reporting environment violations that might happen in their surroundings. Moreover, MCI also is really concerned with influencing the Environmental Agency to take this issue more seriously and put it as on one of their priorities.
After several talks and consultations held among the stakeholders, the targeted housing developer has agreed to modify their site plan to accommodate a more environmentally friendly landscape. Not only speaking in terms of regulatory language, the engagement was also emphasizing how better storm water management can actually benefit them physically and socially. Aside from improving area infiltration capacity, having a properly designed swale as part of their landscaping approach can actually give the neighborhood better aesthetics. Along with that, dry well construction will help them to avoid inundation during heavy rain and it is always good for a property developer to stay out of news that mentions any flooding associated with them.
These two storm water management interventions of course should be built on top of the standardized drainage system. It is also important to note that permeable paver and green space should be there as well but simple requirements like this are often not well complied with especially without proper monitoring and control from the government. The willingness from the targeted housing developer to accommodate better run-off management needs should be appreciated and seen as a learning process for both the developer and the government. Such a move as this by a developer will not only make their public image better, but also will hopefully encourage other developers to take the same action. This case has proven that communication and coordination among stakeholders will lead to better outcomes and that is what the TRANSFORM program trying to achieve and inspire.
Learning from this issue, Mercy Corps and the ESG team really hope that there will be better land use planning and development in the future. As the Regency continues to develop, stormwater management associated with new construction will need to become more and more of a priority. It will be important for the Transboundary Forum to continue promoting and supporting improved stormwater management requirements being placed on new residential or commercial construction. While it is ultimately the obligation of the agencies to impose stormwater management requirements on new development, the Forum can continue to advocate for strong requirements and act as a watchdog to ensure that stormwater management obligations that are imposed are actually constructed.