Friday, 20 December 2019

Flood risk model

Local Community Engagement 1, 2, 34, 5, 6, 7, 8, 910 &11

[Update 1: Part 12 describes Cambridgeshire Parishes affected by sea level rise
Update 2: here is a Story Map that explains the background info to this project
Update 3: this Story Map relates flash floods and not river or coastal inundation

Further to coastal inundation and temperature regime models, DEFRA offer yet more open data with their Risk of Flood from Rivers and Sea. Their v.1.8 for Dec. 2019 hosts Mar. 2018 data decribed here and posted here. Quoting their product info:

Uses local water level and flood defence data to model flood risk across 40 different flood
likelihoods. Results are put into categories and checked by local experts.
• Assigns a suitability rating, which provides information about how suitable the data is for
different uses.

A spatial dataset [...] with the floodplain split into 50m x 50m cells and each allocated one of four flood risk likelihood categories:
• High: each year, there is a chance of flooding of greater than 1 in 30 (3.3%).
• Medium: each year, there is a chance of flooding of between 1 in 30 (3.3%) and 1 in 100 (1%).
• Low: each year, there is a chance of flooding of between 1 in 100 (1%) and 1 in 1000 (0.1%).
• Very Low: each year, there is a chance of flooding of less than 1 in 1000 (0.1%).

This is an excellent complement of landward water run-off models, to seaward coastal inundation models posted here already: We showed incremental sea level rises against OS Open Data and Climate Central elevation data (DEM). The same way we showed a comparison map between the two DEMs, let's compare OS Open Data sea level rise model against DEFRA flood risk map:

click to enlarge or go to map

Click the link, pan & zoom in a little if needed, and move the slider back&forth to see how the two model compare.
The difference is: DEFRA models flood risk from water runoff, whereas coastal inundation models  incremented sea level rise (SLR) against OS Open Data DEM. 

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