Making a Flood Simulation Model with Open Source Tools in Zanzibar.

The Problem

Most of the drainage systems in Zanzibar are blocked by impediments such as uncollected solid waste, accumulated rubbish materials, and informal buildings that prevent water from flowing along their streams and into drainage infrastructure.

During data collection we also found that many communities dump waste directly into the drainage system, blocking its flow. The failure to control these blockages, results in major threats toward urban development and negatively impacts infrastructure in Zanzibar.

There is no one place where the community or government can see the problem of flooding, understand it, and take appropriate measures.

The Solution

The solution is to create a web map, where people and communities in general can see where flood zones are. For example, if someone wants to build a home in a certain area, they will be aware of the risks.

The Process

The first step was to go to the site and do data collection. Specifically, this was done in the areas of Sebleni Nyerere and Mwantenga. Some of the data was already collected, for example, the district and ward boundaries, as well as the terrain data. Afterwards, we checked the data quality and to see if anything was missing. Combining with other available data, and using the open source software QGIS with the InaSafe plug-in, we analyzed the proximity of the potential floods to infrastructure.

The Results

Using the above data, I used the open source modelling HEC-RAC software to create a flood simulation model. In the model you can see how the water is flowing and affecting settlements.

Also, I designed an online web map, you can see everything that was collected in the field including blockages, history of flooding in an area, as well as the areas affected by flooding. This Project will help the government and community to understand the flood zone.

Next Steps

The following are three examples of potential next steps. First, the government and Zanzibar urban planners can look close to natural water bodies that affect the community, and using data and models can better plan settlements so that people are safe.

Second, the Zanzibar Municipal Council should also monitor waste entering natural water sources and waterways that cause the blockage of drainage. Using open data and mapping can help identify where these blockages exist and cause problems.

Third, the Zanzibar Water Authority (ZAWA), is the main authority of water in Zanzibar that can help the government to determine all sources of water and how to manage them. The mapping and data can also support public health improvements, specifically in proper water supply routes by avoiding areas that are frequently flooded.

This video we can see how the water flows to the community based on the flood model.

SOFTWARE and TOOL: -

This flood simulation model is a GIS project that was developed under Open Skies Fellows purposely to develop youth’s innovative ideas in technology.

FOUNDER

“Open Skies Fellows” is a fellowship program led by OpenMap Development Tanzania in collaboration with Uhurulabs and the Humanitarian OpenStreetMap Team, designed to support youth and give them a chance and responsibility to gain social technological skills to leverage their potential to solve community challenges using technology.