Flood Lagoons? What Flood Lagoons?

Posted by alexkemp on 24 June 2016 in English (English)

On the Bing imagery within JOSM and (sacrilege!) Google maps (make sure that ‘Earth’ is enabled) you can find a Flood Lagoon nestled amongst all the Nottingham houses in Carlton, Nottingham NG4. The problem is that OSM does not have a “man_made:flood_lagoon” key/value, so I cannot show it to you on the OSM map (I made up what seemed to me to be the closest to what it should be but, of course, will neither store it nor show it).


I was surveying the even numbers on Foxhill Road Central on Monday 20 June when I came across a kiddie’s playground at the corner-junction of Foxhill & Carnarvon Grove. See if you can spot in this picture the single sign of this flood lagoon (hint: it is the locked-gate entry to a narrow strip of grass + workman’s hut at the back of the playground):—

Carnarvon Grove Play Area hiding a flood lagoon

My spider senses were tingling, but none of the locals that I asked knew what the hut was for.

Whilst entering Foxhill Road houses on to the OSM Map the next day I came across the Flood Lagoon on Bing, and very mysterious it looked indeed. I contacted Severn Trent & explained what I was doing & asked what on earth it was. She got out her own map & it was then that I discovered that it was “Flood Lagoon 5805”. I put it up on OSM, even though I knew that I was just wasting my time.

Yesterday (Thursday 23 June) I returned to survey the odd numbers on Foxhill. This time I was determined to see if I could get a photo of the lagoon. Fortunately for me there turned out to be a clear view of the lagoon from Radcliffe Gardens at the rear of Foxhill Road. I took a number of photos; unfortunately, I was also testing a new camera app on my phone, and some of them have simply vanished into the void. Two frames are left:—

Flood Lagoon 5805 pic#1 Flood Lagoon 5805 pic#1

Coda 1:

Thanks to some fast comments I’ve been able to find a tag documented on the OSM wiki (Tag:landuse=basin) that least allows me to show it to you on the map: Flood Lagoon 5805. That provides a viewable-outline in JOSM. Sadly, no outline in ordinary circumstances in, although the name can be searched for (“5805” could not be found previously).

Coda 2:

(Sunday 26 June)
…and now I am mighty confused. Flood Lagoon 5805 is identical in OSM to what was there before, but now shows on the map as a blue-infilled area. Is this due to some caching-issue on the server, or has there been an update in the tile-server?

Coda 3:

(Monday 27 June)
Carlton Foxhill Road Central Flood Prevention Lagoon:
(a flood prevention lagoon operated by Severn Trent) (contained within the area 426553952)

Sluice Valve 5805 (at the Pitch Close end) empties surface water from the Fairway Drive estate into the concrete channel of the lagoon. Water run-off can come from both playing pitches to the north-west of the Sports Centre and also from allotments to the north of the estate. The course of the concrete channel follows that of a stream which formerly ran here prior to development in the early part of the 20th Century (all such streams are now culverted).

Sluice Valve 6714 (at the Playground end) empties all contained water into the Carlton Foxhill Road Central CSO. That culvert (as long as I recall this information correctly, from an engineer that called me today) ends outside the Old Volunteer Pub on Burton Road.

The land surrounding the concrete channel between the 2 sluices has been graded into a deep basin to temporarily contain exceptional volumes of water during storm conditions.

Note: Severn Trent does NOT give this lagoon any name; I have therefore assigned it a sensible name for search purposes. Many thanks to Philip & others at Severn Trent for patience & explanations.

Location: Carlton, Gedling, Nottinghamshire, East Midlands, England, NG4 1SR, United Kingdom

Comment from SimonPoole on 24 June 2016 at 18:28

See you might want to add a specific value for floods ….

Comment from alexkemp on 24 June 2016 at 20:39

Thank you Simon & Andy. Checking Tag:landuse=basin seemed to hit the mark on the description, if not the tag value (‘basin’ is not exactly the obvious word to describe a Flood Lagoon):— > An area of land artificially graded to hold water.

On an inspiration, I left “Tag:ref=5805” in place and added: “Tag:name=Flood Lagoon 5805”. It now both shows in JOSM (though not in the standard map - boo!] and can also be searched for.

Comment from BushmanK on 25 June 2016 at 00:33

Unfortunately, current tagging seems to be partially messed up.

  • To describe it as a flood lagoon (AKA “detention pond” or “dry basin”), not just some general small reservoir, basin=detention should be added.
  • phone= key must have phone number indicated in international format (there is also newer scheme for it).
  • operator=, landuse=basin, basin=detention and ref= tags together with history of this way making current description= obviously redundant and unnecessary.
  • name= in this case is also questionable: “flood lagoon 5805” is not it’s proper name (like if it were “Foxhill flood lagoon”, for example). It should not be used to make it searchable by specific search engine or software, or to display it on Standard or any other map style. If anyone wants to search for detention all basins (by it’s function, indicated with proper tagging, not by name) or to find a basin with specific reference number, one might want to use Overpass Turbo query (it has quite functional query wizard, so you don’t have to be a programmer to use it).

Boundary contour is a kind of questionable too: basin itself doesn’t occupy the whole fenced territory and deserves own contour, showing its true area. Fenced territory could be properly indicated by separate contour with barrier= tag.

Pretty much space for improvement of small flood lagoon, right?

Comment from alexkemp on 25 June 2016 at 01:38

Hi @BushmanK

Yes, well; I’m fully as capable of ultra exactness, if I want to be. However, the older I get, the more I begin to value my time, and my leniency grows.

  1. I do not personally know whether the specific function is infiltration, detention or retention. You are welcome to contact a Severn Trent engineer to discover which it is, and add the tag accordingly. I’m not going to bother, and particularly as the basin does not even show on the map.
  2. Oh joy! Changing all my phone numbers to International format. Oh! bounteous joy overflowing!
  3. Description remains. I’m a “Belt ‘n’ Braces” man. My trousers very rarely fall down.
  4. It did not have a name before I named it. I’m sorry that you do not like it, but I was the father, not you, so there. Oh! and “Flood Lagoon 5805” is as close as it gets to an ‘official’ name. In addition, try to use Capital Letters & proper curly quotes when you refer to my baby, if you do not mind.

You are welcome to survey the site & change the boundaries if you wish. Personally, and in particular, remembering that it does not even feature upon the map, I’m going to leave it exactly as it is.

Thanks for your interest and comments.

Comment from BushmanK on 25 June 2016 at 02:34


It seems like you accept only those rules, conventions and advises you personally like. Okay, got it, will save my time in other cases.

Comment from alexkemp on 25 June 2016 at 04:39

It is “advice” & not “advises”; ‘advice’ is both singular & plural, all at the same time. But then again, according to you, Mr @BushmanK, that is just my personal rules.

Comment from BushmanK on 25 June 2016 at 15:32


Thank you for correction - English is obviously not my first language, and I appreciate it, when someone helps me to improve it. Unlike you, in case of OSM rules.

Comment from andy mackey on 25 June 2016 at 20:30

Alex this and a couple of others i’ve mapped render.

Comment from alexkemp on 25 June 2016 at 22:58

Oh gosh, @andy mackey, what a cruel link; you are saying that the non-show is all my fault, whilst yours shows wonderfully. Damn, damn, damn. Now I need to phone Severn Trent again to discover what the nature of the basin is. Ah well. Many thanks for your link.

Comment from alexkemp on 25 June 2016 at 23:46

Having planned to possibly survey yet more streets in the locality I went to view it in the map and, godammit!, Flood Lagoon 5805 shows up on the map as a blue-infill area (just as Andy’s did). I checked it using Potlatch and there has been zero changes to my earlier changeset. The fact that it renders now means that all of @BushmanK’s earlier objections become valid, which is most annoying. However, all of that will need to wait until Monday.

Comment from TheSwavu on 27 June 2016 at 02:15

It’s a detention basin. If it was a infiltration basin you would expect if to be wide and shallow with an outlet that was set up to keep the water ponded while it soaks into the ground. If it was a retention basin then the outlet would be set up so that there would be some water still in the basin after it stops flooding (ie: retained).

Comment from alexkemp on 27 June 2016 at 14:51

Further edits made to the Lagoon, following a call to Severn Trent (they are a remarkably helpful set of people; I even had an engineer call me today following my initial call to see if he could help further). The edits have not yet been uplifted, as there are a mass of houses that I’m adding in Second Avenue & nearby streets following another survey yesterday.

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