Land Classification Maps
In most cases, the best ground for aerodromes coincided with the most productive farmland. Comparing maps of airfield locations with agricultural land classification maps, such as the "Great Britain: Land Classification" map of 1944, confirms that wartime airfields were disproportionately sited on grades 1 and 2 (the most versatile and scarce soils). Large, arable fields without banks or walls were ideal for rapid runway construction under emergency conditions.
Military airfields also needed two levels of traffic-ability. First, an inner area with runways and taxi zones with near perfect conditions to minimize wear and tear on the planes, and to allow swift movement of ambulances and fire tenders. Second, an outer area with a free-draining network of access roads of moderate gradient, plus a generous cover of woodland and hedgerows to shelter camp sites from inclement weather, explosions and air raids.
The most easily engineered ground was found in East Anglia, the East Midlands, and Wessex, which was fortunate as it placed the airfields within a shorter striking distance of the enemy.
References and Recommended Reading:
Doyle, P. and Matthew, B. (2002). Fields of Battle: Terrain in Military History. London: Kluwer Academic.