At Grimsthorpe village, the A151 is in the second of the main valleys dissecting the plateau, that of the East Glen river. From its association with Edenham, this river is often called the Eden. The West and East Glens join near Wilsthorpe, at . Through Grimsthorpe and Edenham, there are numerous bends and winds across the small exposures Jurassic soils, glacial gravel and alluvium, until the road climbs out of the valley over the till-capped ridge which separates Edenham parish from Bourne. On the glacial clay soil of the till, it passes between woods, including Bourne Wood.(19)