Market Garden:terrain modelling

This evening I have been transferring, in the dark, terrain hexagons between ManCave2 (storage and preparation) and ManCave1 (playing area).  However, it appears that I am not able to make the necessary terrain (a 3 hex wide river) without some further modelling.

Effectively I need 22 hexagons with a river covering about 80% of the hex but grassy banks on one point.

Back to ManCave2 to reconfigure several of my former English Channel hex tiles…