Rapid Damage Assessment for Floods in Dar es Salaam, October 2020

By Hawa Adinani

Flooding in Dar es Salaam, October 2020. Photo by OMDTZ

In order to respond to flood events, flood mapping and damage assessment help to understand the extent of flooding at a larger scale. It is a basis for having a bigger geospatial analysis of flood damage. This blog explains an approach of flood response by community mapping methods and rapid assessment to determine the extent and damage of flooding.

In response to the heavy rainfalls that occurred on October 13th, 2020, that resulted in heavy flooding and enormous effects including 12 deaths, loss of properties, destruction of infrastructure, dozens of road blockages disrupting transportation in the city, etc — OMDTZ conducted a rapid assessment to produce maps showing the extent of damage caused by the flood. The flooding was devastating as bodies were found floating on the Msimbazi River — the most flooding river in Dar es Salaam.

To conduct a rapid geospatial flood damage assessment, OMDTZ supported by The World Bank conducted community mapping activities by visiting 34 wards (96 subwards) that were mostly affected by floods to produce flood maps that would be shared with the regional disaster management team for proper planning, response, and mitigation of future flooding in the city.

OMDTZ visited the affected wards to work with local leaders by:

  • Conducting meetings with community leaders and identifying the affected areas on A1 printed maps with aerial imagery background for a better and easier visualization when tracing features of the specific places
  • Visiting the field to physically assess the situation, taking geo-points in some of the affected areas using OpenDataKit Collect — a mobile application that we use for collecting data.
Community leaders and OMDTZ team identifying areas affected by flooding. Photo by OMDTZ

After community mapping, the team worked on cleaning data and produced maps from the data collected. Data collected included affected amenities such as schools, drains, health facilities, roads, houses, etc. The data is used to produce inundation maps — a set of maps that shows where flooding may occur over a range of water levels in the community’s local stream or river — showing different themes i.e. severely and partially destroyed structures, and flooded houses.

A screenshot of a map showing health and education facilities affected by the October 2020 floods in Dar es Salaam.

What’s next?

The data has been shared with the World Bank and the regional disaster management committee for further action and proper planning of flood resilience. These are very crucial and important datasets that reflect community perspectives and how they are impacted.

The data can also be used to predict flood events. By recording data from presently flooded areas, it can be useful to identify areas at risk of future flooding. With climate change well underway, people are increasingly interested in predicting ways that flooding will worsen. Flood mapping is the most critical aspect for this.

Using Open Data, Open Source, and maps to solve different socio-economic challenges.