Tuesday 14 April 2015

Releasing data really works, Part VII

And now for something completely different - the original posts until Part VI are listed below - I ran across a nice map of Steve Feldman's: He also tried out free data and software to map UK flood maps, an up-scaled version not for professional re-use.

P-51's at Bottisham Airfield, Cambs, click to enlarge)

I jumped on it to check out a pet peeve of mine. Again in East Anglia near where I live, the new town of Northstowe was purported to have be planned on or near a former air base immediately west of Histon / Impington in CB24. Chatting with locals at the pub, as well as the beautiful vistas offered by the new double-decker Guided Buses from Cambridge to St Ives, told me that airfields were built on flat ground. The Geologist in me quickly found out, by reviewing British Geologic Survey maps online used to the geo-history project, that flat areas happen three ways:
  1. vast former peat bogs that have been dried out and left fallow in Norfolk, as in Cambs. and Suffolk these have been largely cultivated
  2. rare structural surfaces where outcrop surface lie flat at or near the ground level, again more in Norfolk forested and uncultivated areas
  3. silt-lined remains of extensive Quaternary lakes, left behind by the retreating ice-sheets at the glacial rebound forming today's coastline
Of these, the latter were apparently used to create the many airports, serving as military bases during World War II in East Anglia - they offered solid flat surfaces of sufficient extent to build runways in the appropriate orientation w.r.t. local winds and intended destinations (1). Such airfields were, however, not only adjacent to many populated areas, but also being divested by MOD (UK Ministry of Defense) and turned into housing estates - so-called brownfield development is a hot topic as there is a perennial shortage of houses in England. Ordnance Survey Landranger Map 154 details the area:

Northstowe planned area (click to enlarge)

The curious geologist and amateur historian in me also asked, if those were Quaternary lake beds, then what are the chances of them being re-flooded, especially since the last five years saw a marked increase in those events as reported in the news? Would it not be an unfortunate coincidence that new developments be located in flood-plains? The news also reported new housing in river flood-plains elsewhere in England, so that the possibility of my scenario was most definitely there...

So I had the geology and the detailed topography, as well as preliminary investigation of the historic lay of the land, but do I have the flood maps? Without going into the details of flood maps released then restricted for use by real-estate agencies. Steve Feldman provided the perfect illustrative tool for this question:
  1. go to his page and zoom into my area, that has very simplified features
  2. use OpenStreetmap to find the planned municipality of Northstowe
  3. on map Search by District: Longsanton, pan up ½ screen, zoom out 1 step
Et voilà! We have a side-by-side map the the very location in question! Try the links above for yourself, using this as a guide if you are interested:

click to enlarge

You will recognise that the floodplain follows the local creek. Only local knowledge would tell you that the wide swathe near the top, cut by a high bank that was the former railway / current guided bus way is a former lake bed currently occupied by woods near Longstanton. For obvious reason former MOD land and historic airfields are not shown, but a little further scrutiny finding old paper maps with local village historic societies, the Cambridge or the British Library may shed more light here. There are also the published maps around the Northstowe public consultation process.
But for now from a cursory glance it appears like, even though there are significant flood-risk areas and worrisome widening of same, we needn't fear that housing estates sit atop re-floodable areas. And of course the proof of the pudding is in the making, seeing where the estates are built... and what hand Mother Nature will deal us in the future?

Releasing data really works, Part VI - review and catalog of free geodata available for Great Britain
Releasing data really works, Part V - East Anglia geohistory rapidly stood up on AWS GeoCloud2
Releasing data really works, Part IV - corrections from QC of  Parrish boundaries sent back to O|S
Releasing data really works, Part III - Guardian Data Blog railway traffic on GB postcode centroids
Releasing data really works, Part II - repost complex Neolithic research data on UN data backdrop 
Releasing data really works! - original about posting East Anglia geo-history data on O|S Parishes

1:  a lot of this was picked up earlier, when dealing with US, UK, CDN and AU Departments of Defense, whilst collecting data for publication on CD-ROMs prior to the internet era while I was in Canada, as well as a lifelong interest in aircraft and years of travel and fieldwork all pre-1990s 

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