Wednesday, 27 November 2019

Local Community Engagement, Part 7

[Update: Part 8 on temperature anomaly scenarios adds further parameters in the debate.]

Part 1 introduced this project to engage local residents in villages north of Cambridge UK. Part 2 elaborated on some resources available and communication via Story Maps. Part 3 looked at three more resources, introduced an open call and closed with an Elevator Pitch. Part 4 looked at community engagement's key differentiator, to search for local info your way, not the search engines'. Part 5 introduced our own Wikipedia Gazetteer map to complete our infrastructure guide of "What is in Cambridgeshire?" And Part 6 is a manifesto of sorts, in the form of a draft press release.

I have since created from Open Data and written in Medium a number of climate change models with regards to sea level rise and coastal inundation. This arose from a statement in my new Cottenham Open LinkedIn channel:
What will East Anglia look like after sea level rise, and in what  time-frame? There's no community engagement without knowing your environment!

Coastal inundation

Let me start with three statements in the literature that should alleviate any concerns around either sensationalising or debunking Climate Change in the press:
  • Climate Central, whose data are used here, said in Nature Communications: “experts now estimate there is a 5 percent chance 21st century sea-level rise will exceed 2 m.”
  • some to&fro-ing with Climate Deniers brought up the aspect of coastal subsidence & glacial rebound I know&love as a geologist - some coastal regions  like Houston or Bangkok slide into adjoining gulfs as they sit on soft sediment, other regions like Arctic Canada and East Anglia have risen slightly as Quaternary ice shelves disappeared - Deniers wish they'd never asked...
  • right on cue, NASA / JPL scientists  modelled Antarctic ice sheets incl. aspects of the above, and they “ estimated that projections [for sea level rise factoring subsidence &/or rebound] for the next 100 years are within about 1% of previous projections for that same time period. ”

Cambridge North

(click to enlarge)
The only thing that matters is this map of possible coastal inundation from 2 m. sea level rise by century's end: Hold your beach balls, parasols and deck chairs... neither Waterbeach nor Landbeach will become beaches anytime soon!

Blue shows possible encroachment, and green the land as we see it now. The top map is drawn from Ordnance Survey Open Data direct calculation of local surveying. The bottom one is from Climate Central's recalculation of previous global topographic maps derived from satellites, and projected correctly to local conditions. The model is simply to mask in blue where it is less than 2 m. above current mean sea level, and to leave transparent everything else. You thus see current topography and new high waterline.

East Anglia

This doesn't mean that all's well, however, as a third of East Anglia will still be inundated as shown:

OS Open Data (L), CoastalDEM (R), below sea level (blue), +2m. inundation (white)

Spatial statistics on the map show that 17% (L) & 14% (R) land is below sea level today in the area above. A simple 2 m. sea level rise will put 32% (L) & 28% (R) land below sea level. Note that these are straight elevation statistics, not environmental modelling such as absorption, run-off etc. And while current sub sea level structures help drain the Fens, such a sea level rise would inundate around 30% of East Anglia! Details tabled here.
That's an average 32.5% increase: in other words a third more of the land would become un-arable in East Anglia, England's breadbasket
As mentioned in Medium above, part of the climate change risk & mitigation efforts revolve around coastal inundation. We started with a time frame and probability, and we end now with are areal estimate from simple modelling. Again as mentioned in Medium above, all of these are based on relatively simple maps that can be derived by you, concerned citizens, to help you sort fact from fiction.


Here are the results above tabulated for detail and context:

(click to enlarge)

No comments:

Post a Comment