NbS: Analyse flood risk

Modified on Mon, 27 Mar 2023 at 04:01 PM

When identifying the risk of non-permanent, an important natural risk to consider is flooding. This template project allows us to look at areas that have at some point since 1984 been inundated with water. This can allow you to see, plan for, and act on fire risks. The data visualises the area covered by water either on a permanent basis where there is water year-round (e.g. lakes and rivers) or on a seasonal basis where there is only water cover for part of the year (areas that have been flooded or are part of wetland ecosystems). This workflow shows the average coverage for each type of water extent, and also the maximum extent since 1984. Comparing the average with the maximum enables you to make an assessment of your project site.


Demonstration Video

What should I use this template for?

You should use this template project to look at historical water coverage for a given location. This can help you to assess the likelihood that a location might have been flooded and therefore could flood again. This could either be a large area (as in this example, where we are looking at Cambodia) or in one or more project sites (here we are looking at 5 different project sites). This can help you to understand the role flooding might play as a risk factor for non-permanence.

What data has been used?

The data used in this template is the JRC Yearly Water Classification History dataset. This dataset provides a year-by-year classification of surface water, its location and its permanence between 1984 and 2021. Each pixel in the image is 30m x 30m. Areas of Permanent water are where water is identified in every month of the year, whilst Seasonal water is where water is identified at least once in a year, but not for the entire year.

This dataset is not best suited to get a very accurate look at the impact caused by a particular flood event but provides good high-level information over a long time period. It is also not suited for near-real-time identification of flood events.

What do the outputs show me?

Map Outputs

This template project has two map output layers. The layer called Average Water Extent shows the most common classification for surface water between 1984 and 2021. The legend on the left-hand side tells us that permanent water is dark blue, and seasonal water is light blue. An area that is classed as seasonal water means that it normally experiences some surface water for part of the year.

The other map layer is called Maximum Water Extent and shows the maximum extent of surface water between 1984 and 2021. An area that is classed as seasonal water means that at some point since 1984 it has experienced some surface water coverage.

Dashboard Outputs

If we look at the dashboard tab, you will see that we have two tables. This details the area (in hectares) for each type of water coverage; seasonal or permanent. It distinguishes between each of the five project locations. Each table either shows the average surface water extent, or the maximum surface water extent. The tables can be downloaded as a CSV spreadsheet using the download button at the bottom-left of the table. This is true of all tables created with Earth Blox.

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