Tens of thousands of people are displaced every year by flooding in the Jabodetabekpunjur area, which contains Jakarta – Indonesia’s densely populated capital – and surrounding cities. This is despite considerable investment in infrastructure such as water pumps and large drains.

The government of Indonesia published a regulation highlighting the need to improve the conditions of natural and artificial lakes throughout the area. These lakes play a vital role because they capture excess water from rainfall. Lakes are frequently lost or damaged due to unmanaged city growth, or through sedimentation. It is estimated that lost lakeland could increase the cost of flood damage by up to USD 17 million annually. Policymakers were hampered in their understanding of the problem by the absence of data more recent than 2019.

The Approach

The Indonesian Government’s National Land Agency’s Project Office partnered with UNDP’s Accelerator Lab Indonesia and OpenStreetMap to collectively generate a map of the location and condition of over 200 lakes in the area. Local surveyors were recruited from near the lakes to gather responses to community surveys. This information was later supplemented by geolocation data from satellite images. The project gave policymakers insights after only two weeks of data collection.

The Benefits

This project brought together multiple data sources to give policymakers quantitative and qualitative insights into the nature of the lakes, such as their changing size and what management is required to ensure that they capture excess rainfall. The collective mapping of the lakes highlighted the need to invest in and strengthen the digital and physical infrastructure in affected communities.

The community data will be used by local policymakers to introduce measures that respond to the root cause of damages to the lakes, such as introducing clear guidelines on ownership, maintenance and responsibilities. The project thereby contributes to SDG 11 Sustainable cities and communities. It also gives an overview of the quality of water sources in Jabodetabekpunjur and so supports SDG 6 Clean water and sanitation.

1.47

Billion

people globally are exposed to substantial risks due to flooding.

Indonesia

The context

Floods are one of the most common natural hazards, with an estimated 1.47 billion people globally exposed to substantial risks as a result. Most of the at-risk population live in low- and middle-income countries.

Indonesia has the third highest absolute population exposure to flooding, with 76 million people or 27 percent of its residents vulnerable to flood risks.

Combining geospatial data with local survey insights

The aim of the project was to combine geospatial data and localised survey insights to enable policymakers and urban planners to makes sense of macro patterns (such as climate change) and micro trends (such as the custodial role played by communities). Local surveyors from near the lakes were recruited to gather responses from communities. They took part in training session that focused on technical skills for the mapping process. The data collected on the ground was then combined with geospatial data and verified against satellite imagery of the lakes. The project generated novel findings that updated the static map of the area that policymakers were previously relying on. A new dynamic map of the lakes was generated.

Figure 1: Extract of the new dynamic map of lakes.
Source: Posts - Pemetaan Situ - Pemetaan Situ (ushahidi.io)

Main findings from the collective mapping

One of the main findings was to establish which lakes and what overall proportion of lakes were at an increased risk of flooding. It also identified that, contrary to the initial assumption that all lakes were under management, only 45% of lakes were looked after by a lake administrator. Such lake administrators play a pivotal role in managing the water-flow by opening or closing floodgates and regularly cleaning the lakes. This was identified as a top priority to remedy and in response policymakers developed a lake management protocol to set out clear responsibilities for undertaking these tasks. The mapping also uncovered additional findings, such as identifying lakes that have experienced a change in function and documenting what flood mitigation efforts communities were undertaking.

How can better data contribute to better policy?

The bottom-up and participatory approach taken in mapping the lakes illustrates the great potential for involving citizens in tackling global problems such as urban and semi-urban flood mitigation. A citizen science model, whereby data is collected by the public to be later verified and analyzed by experts, provides the opportunity for a future where empowered citizens are able to contribute to evidence-based decision-making.

Where do we go from here?

The project piloted a novel and participatory approach towards data collection for the public good. The positive feedback received from regional governments and citizens provides a foundation for similar projects to be replicated and the methodology to be adapted in other contexts. In the longer term, such approaches will improve public decision-making both at the government level and by empowering citizens to make more informed decisions in their own communities.