Engaging the Crowd: Mapping Lakes in Jabodetabek-Punjur for Flood Mitigation

Engaging the Crowd: Mapping Lakes in Jabodetabek-Punjur for Flood Mitigation

Floods are a relatively common occurrence in Indonesia due to the country’s geographical location, climate patterns, and natural topography. Indonesia experiences riverine and coastal flooding, varying frequencies depending on the region. Over the years, the densely populated capital and its surrounding cities (Jakarta, Bogor, Depok, Tangerang, Bekasi, Puncak, and Cianjur or Jabodetabek-Punjur) have experienced catastrophic flooding, most recently in 2020. The capital was five meters underwater in the 2007 floods, which were the worst to date. A damage cost of around 5.2 trillion IDR, or $400 million, was incurred due to the dozens of fatalities, thousands of displaced people, and days of city paralysis. Several of the regional government’s efforts are implemented to reduce flood loss, such as water pumps, large-scale drains, and rivel normalization programs; however, flood continues to be a significant problem. To solve this problem, the Ministry of Agrarian Affairs and Spatial Planning established a Project Management Office (PMO) based on the Presidential Regulation No. 60 of 2020. According to PMO, one of the leading causes of these floods is the decreasing capacity of rivers and lakes to drain water effectively. Therefore, a significant effort is necessary to improve the functionality and condition of natural and artificial lakes in the Jabodetabekpunjur area by enhancing the citizen to promote transparency in data and policy through an interactive map.

Lake Restoration to Reduce the Flooding Risks

The health of the lakes is frequently ignored during the development of infrastructures in Jabodetabek-Punjur. The lakes play a crucial role in flood mitigation by acting as storage areas for water, serving as detention or retention basins, and providing a critical means of reducing flood risk. Not only that, the decreased area of the lakes also has the potential to worsen the flood damage for the nearby communities. Thus, initial restoration efforts have revealed a wide range of intricate factors that contribute to the functioning of the lakes, including land issues, population growth, sedimentation, and physical alterations. These efforts should also be implemented to avoid the economic loss from changes in the lakes’ functionality, estimated to be IDR 250 billion or US$ 17 million annually. Indeed, increasing and preserving the lakes’ condition become the local government’s responsibility. However, involving the citizens in flood mitigation will result in more effective potential when the planning is conducted.

Distribution of lake locations in Jabodetabek-Punjur (OpenStreetMap contributors, 2022; Perkumpulan OpenStreetMap Indonesia, 2022)
Distribution of lake locations in Jabodetabek-Punjur (OpenStreetMap contributors, 2022; Perkumpulan OpenStreetMap Indonesia, 2022)

Citizen Science in the Lake’s Restoration

Before undertaking the lake restoration project, it is crucial to have access to spatial data regarding the location and condition of the lake. The Ministry of Agrarian Affairs and Spatial Planning states that there are 218 lakes within the Jabodetabek-Punjur region. However, the available information only consists of the coordinates of these lakes and needs to include their current environmental, social, and economic conditions. Therefore, in order to assess the lakes’ potential for flood mitigation, an updated dataset needs to be collected. Perkumpulan OpenStreetMap Indonesia (POI), in collaboration with UNDP Accelerator Lab Indonesia and the PMO, has undertaken the task of collecting the necessary lake datasets for over 200 natural and reservoirs in the Jabodetabek-Punjur area.

A Framework of Citizen Science in the Lake’s Restoration

The collection process involves two distinct approaches: remote mapping and field data collection. Remote mapping entails gathering geospatial data through satellite imagery or aerial photography on the OpenStreetMap platform, eliminating the need for physical presence at the location. Prior to conducting field data collection, remote mapping is utilized to map the lake and its surrounding features, including elements that relate to the social and economic conditions of the area. These elements encompass local residences, markets, shops, and restaurants contributing to the community’s economic well-being. Remote mapping plays a vital role in establishing a plan before initiating fieldwork, and through the efforts of the POI, 170 lakes were successfully mapped. To support this activity, the POI organized an online training and mapping event for the public called Mapathon. During this event, participants utilized OpenStreetMap to contribute to mapping the lakes and provided detailed information about each lake through Ushahidi on August 2, 2022. As a result, 18 contributors successfully mapped 58 lakes

Field data collection becomes highly valuable when there is a need for comprehensive, accurate, and real-time information or when the available remote sensing data needs to cover the area of interest adequately. It allows for collecting crucial physical and environmental information about the lake, including the condition of inlet and outlet doors and water quality indicators like depth, odor, and discoloration. These details can be challenging to capture remotely. Field data collection occurs after the completion of remote mapping for both the lake and its surrounding areas. During a specific period from April 11 to April 24, 2022, a dedicated team of 12 surveyors embarked on the mission of collecting qualitative data about the lakes. The surveyors effectively usedUshahidi and Mapilary, a freely available and open-source platform, to ensure the real-time conditions observed across all 170 lakes were accurately reported. In this process, the surveyors were required to take the lake photo using Mapilary and respond to a set of questions concerning the physical and environmental conditions of the lakes using Ushahidi, which POI and UNDP Accelerator Lab Indonesia formulated.

Field Surveying Activities

Transforming Lake Mapping with Collective Efforts

Both remote mapping and field data collection have strengths and limitations. However, combining these two approaches allows for a more comprehensive and accurate understanding of a study area. This combination of data sources will enable policymakers and urban planners to understand long-term trends, such as the impact of climate change and population growth on the shrinking of lakes in the region. Therefore, the analysis findings will provide valuable spatial information on future lake restoration programs for flood mitigation and identification of the stakeholders for effective lake management.

Field Surveying Results

In the previous stages of our project, the remote mapping process successfully generated comprehensive maps of the lakes and the adjacent structures by analyzing satellite imagery. However, it was crucial to complement this remote data collection with on-site field surveys. Over a period of two weeks, a team of 12 dedicated surveyors gathered invaluable information that couldn’t be captured through remote mapping alone. The report generated by the surveyors unveiled significant findings. It revealed that approximately 34.7% of the lakes surveyed lacked inlet doors, while 65.3% had them properly installed. Regarding outlet doors, 31.25% of the lakes were observed to be without them, while 68.8% featured functional outlets. Furthermore, the surveyors evaluated water pollution based on visibility and odor, finding that 44.1% of the water was polluted, 50.6% remained unpolluted, and 5.3% had no data due to land cover change on the lake.

To gain deeper insights, the surveyors interviewed the local communities who live around the lakes. The results indicated that out of 170 lakes, 63 were not under government management. Consequently, 44.1% of the lakes suffered from pollution due to inadequate oversight. The local communities identified several key factors contributing to this pollution, including fishing activities, the discharge of waste from factories and households, the conversion of 14 lakes into residential zones, and the ten lakes shrinking for farmlands and fishponds.

Leuwibatu Lake as one of the shrinking lakes into the farm (left) and Jambu Lake as one of the land cover changes into a residential area (right)

The interactive lakes mapping dashboard application, Ushahidi (https://situ-jabodetabekpunjur.ushahidi.io), serves as a comprehensive repository for all the gathered data, documenting the findings of this mapping project. The project’s primary objective is to utilize open source and public platforms to improve the accuracy and reliability of government data, promote transparency, and drive digital advancements at the city level. These objectives are in-line with the use of Ushahidi to utilize user-generated reports to collate and map data. In total, 228 lakes are displayed; 170 lakes from field surveying activities and 58 lakes from the Mapathon event. It shows that Ushahidi is really powerful for enhancing citizen science for collecting data. Through an interactive map, the government gained access to detailed spatial information that faithfully represents the conditions on the ground. 

The valuable insights derived from the field surveys shed light on the structural characteristics of the lakes and provide a more holistic understanding of the ecosystems involved. This emphasizes the urgent need to address pollution issues and implement effective management strategies to protect the well-being of these lakes. Considering the potential for tourism development and flood mitigation, it becomes crucial to prioritize infrastructure development and amenities around the lakes, creating economic opportunities for local communities. Simultaneously, efforts should be directed toward maintaining and improving the natural outlets and inlets of the lakes to regulate water levels during periods of heavy rainfall. Preserving and restoring wetlands and surrounding vegetation also significantly mitigate floods by efficiently absorbing excess water. However, achieving these desired positive outcomes requires the collaborative efforts of all stakeholders. By working together, these lakes’ restoration and sustainable management will ultimately benefit the communities and the environment.

Accessible, Quality, Open Geospatial Data for All