Floods in the neighborhood: Mapping poverty and flood risk in Indonesian cities

By Jun Erik Rentschler, Christoph Klaiber and Jian Vun

Over the past 20 years, floods have displaced more Indonesians than any other disaster type, causing significant damage and disrupting local economies. The poor and vulnerable often bear the brunt of flood hazards and are affected disproportionately. They tend to live in hazardous areas such as dense settlements situated below flood levels, highly-exposed coastal areas, and along riverbanks that often overflow. They also often have limited access to financial services and basic support to cope with the aftermath of flood events.

For example, the Indonesian city of Bima is prone to fluvial flood hazards (from overflowing rivers and insufficient drainage capacity) and coastal flood hazards (from rising sea levels and storm surges). The city has experienced increased economic activity, urban development, and population growth. Housing settlements along risky river and coastal areas have expanded and have limited compliance with current building codes and flood risk mitigation standards (such as building above flood levels and use of flood resistant construction materials).

Floods threaten to reverse years of socio-economic progress in one swift event. The effects could be especially devastating in poorer communities and neighborhoods, where flood protection, drainage, and sanitation infrastructure is often less developed and communities and assets are more vulnerable.  Governments can take action to better protect and empower vulnerable households, for instance through flood resilience investments in neighborhoods where risks are most acute, supporting flood preparedness, and addressing socio-economic drivers of vulnerability (e.g. by improving access to services).

1 in 4 Indonesians live in high-risk flood zones

In an earlier global high-resolution study we had estimated that 1.47 billion people live in high-risk flood zones, 956 million of which live in East and South Asia. Globally, 587 million flood exposed people were estimated to live in poverty (living on $5.50 per day or less) and 132 million people in extreme poverty ($1.90 or less). For these groups, floods are likely to leave the most devastating long-term consequences on livelihoods.

In Indonesia, 76 million people live in high-risk flood zones, which is about 27% of the population or more than 1 in 4 Indonesians. Out of these 76 million Indonesians, 40 million live in poverty  (on less than $5.50 per day), and 2.6 million in extreme poverty (less than $1.90 per day). Overall, we find large variations in flood exposure across provinces; West Kalimantan has the highest share of population exposed to high flood risk with 44 %. Gorontalo is the province with the largest share of the population that is both flood-exposed and living in extreme poverty (3.9 %). 

Analytical tools can help us identify local risks and target actions

To better understand the scale of flood risks in Indonesian cities, we conducted a rapid assessment of people’s flood exposure in three Indonesian cities: Bima, Manado, and Pontianak, that are potential pilot cities for a proposed national urban flood resilience program. We used the methods and results from the global study, and adapted them to local contexts. Using socio-economic data for city subdistricts (kecamatan), we took the analysis from a global to a neighborhood level. We combined these with  flood hazard maps based on hydro-topographic models and high-resolution population maps.

2 in 3 residents of Pontianak face acute flood risks

The results show that Pontianak, Bima, and Manado face heightened risks. Flood risks are acute in many of their subdistricts, especially along riverbeds, flood basins and shorelines.  Our estimates suggest that 64% of the population (415,000 people) living in Pontianak face a high flood risk, while in Bima 28% of the population (13,000 people) and in Manado 18% are exposed to high flood risk (40,000 people).

But which neighborhoods are most vulnerable? Especially in fast urbanizing areas, poor people can be pushed into flood-prone areas by lower housing values and rents associated with the higher risk and poor-quality infrastructure. This makes low-income neighborhoods particularly vulnerable to experiencing disproportionately severe and long-lasting flood impacts. The analysis offers a rapid assessment of flood risk and poverty levels in all subdistricts of all three cities. We identify four subdistricts where very high flood risk (over 20% of population exposed) coincides with poverty rates above the national average. Three of them are in Bima city. In several sub-districts of Pontianak, more than half of all residents are exposed – in Pontianak Timur it is 99% of all residents.

This analytical approach can rapidly analyze the social vulnerability of cities and identify subdistricts with the highest vulnerability to floods. It shows how global tools can be quickly adapted to local scales to assist governments to identify and prioritize investments in urban flood resilience. Our data-driven analyses can help to mitigate harm from increasing flood risks and target the most vulnerable areas for more targeted actions.

Actions are needed in the face of mounting risks

While the assessment highlights that risks are already high in many communities, rapid urbanization, land subsidence, and climate change will only heighten the risks in the coming years. To safeguard the prospects of resilient development – especially in coastal towns – actions are urgently needed to reduce risks and the socio-economic drivers of vulnerability . Hence, the World Bank is supporting the government of Indonesia to establish a national urban flood resilience program, including through the proposed National Urban Flood Resilience Project and through technical assistance financed by the Global Facility for Disaster Reduction and Recovery. The national program intends to reduce the vulnerability of poor and vulnerable households living in flood-exposed areas of participating cities, investing in demonstration projects across the country.