|Kent - 7m sea level rise - flood.firetree.net|
Although not central to the story, a flooded England - in this case, the setting is Kent - is nevertheless part of the scenario. London is submerged, recalled in a dirge-like working song ...
London Town is drownt this day
Hear me say walk a way
Sling your bundel tern and go
Parments in the mud you know
Greaf and woe dont you know
Pick it up its time to go
... and Kent is governed by a regional government ("the regenneril guvner men") from "The Ram", its eastern headland that's now an island. Its separation is recalled in legend as a catastrophic event:
"... there come a jynt wave it wer like a wall of water hyer nor a mountin. Dint it come tho. It come rushing it come roaring it come roaling down it cut acrost the lan right thru from Reakys Over down to Roaming Rune. It cut the Ram off sepert from the res of Inland that wer the day the Ram be come a nylan."
Russell Hoban did his homework on the geography. The map of Riddley's part of "Inland" at the beginning of the book matches very well the projected coastal profile (see above) from a sea level rise of 7m or so: the excellent Riddley Walker Annotations site has a nice version of Hoban's map by Barbara J Becker - Map of Inland - superimposed on a present-day map. The annotations note that "Reaky's Over" is Reculver, and "Roaming Rune" is Richborough Castle (i.e. a Roman ruin); all of the placenames in Riddley Walker are, like the language itself, plausibly mutated through what appears to be a grimly comic and rather scatological mindset.