650 whitmore. MILITARY GEOLOGY [Ch. 34 



following aspects of airfield siting and construction: drainage and 

 possibility of flooding; bearing strength; sources of gravel and crushed 

 rock for base course, surface course, and concrete aggregate ; and water 

 supply for construction, maintenance, and human consumption. 



In time of war, military airfield-site selection is unique primarily in 

 that the geologist or engineer must select sites in areas he has never 

 seen. With sufficient information, it is possible to select an actual 

 runway location and describe subgrade conditions in considerable de- 

 tail, or to determine the possibility of enlarging an existing field. 



The methods of site selection differ, of course, with the amount of 

 available information. The most difficult situation, where data were 

 almost completely lacking, is exemplified by the selection of sites in the 

 Solomon Islands by the Military Geology Unit in 1942. Geologic in- 

 formation was even more meager than topographic data; aerial photo- 

 graphic coverage was scanty or lacking. The only topographic in- 

 formation was on hydrographic charts on which the inland topography 

 was indicated in a very general manner by hachures. With the help 

 of scattered and general ground descriptions, and geologic interpre- 

 tations based on analogous regions, areas were outlined within which 

 the best sites were likely to be found. 



On Guadalcanal Island the most suitable part for airfields seemed to 

 be the coastal lowland along the north side (Fig. 3, areas 10 and 11). 

 Several good anchorages were known along this coast, and these made 

 it readily accessible. The eastern part of the lowland (area 11) was 

 known to be thickly wooded, and large trees would present a clearing 

 problem, whereas the western part (area 10) contained open patches of 

 tall-grass prairie. By analogy with similar coastal plains, the lowland 

 was expected to be an undulating plain within which expanses of level, 

 fairly well-drained ground sufficiently large for airfields could be found. 

 Some filling or diversion of small streams was anticipated for long run- 

 ways. From its shape and position near the mouth of a large stream 

 (Lunga River) , Lunga Point at the west end of area 10 was described 

 as a probable delta (hence poorly drained and less suitable for air- 

 fields than other parts) . Because of the heavy rainfall, water supply 

 would be adequate everywhere. 



The Guadalcanal landing was made on the beach east of Lunga 

 Point. Henderson Field was constructed on the site of a small Japanese 

 airstrip on the grassy plain at the inland edge of the Lunga River 

 delta. Another large airfield was built farther east within area 10. 



When engineers are on the ground, ready to begin construction in a 

 selected area, preconstruction reconnaissance is, of course, necessary in 

 order to locate the airfield in the most advantageous position and to 



