PUTNAM 



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impermeable, which means that water does not sink into it very far. The result is that seasonal 

 vegetation with short roots, such as grass, dominates. Back in the mountains where the rocks 

 are more permeable, slopes are mantled by a permanent vegetative cover of thick, thorny 

 shrubs and bushes that are virtually impenetrable. The fire hazard is very high during the 

 summer dry season, and fire in this country introduces all sorts of operational difficulties that 

 will not be encountered in a more humid region. 



Figure 5 is a good example of the complexities that must be faced in setting up a classi- 

 fication. An excellent beach fronts the shore, but its value is reduced by the coastal lagoon and 

 tidal marsh that constitute a formidable barrier denying access from it to the land, as well as 

 by the fact that it can be taken under observation and fire from the nearby mountains. The 

 mountains have about the same structure and vegetative pattern as those in the preceding photo- 

 graph and like them are characterized by a high correlation between rock type and the distribu- 

 tion of the plant cover. 



The coast shown in Fig. 6 is for the most part an extension of Professor Smith's talk. In 

 fact he showed a slide of essentially the same region as this, not far from Santa Maria, Califor- 

 nia. This is a very exposed coast. Landings are difficult, but are possible. Once ashore the 

 problem of dispersal is paramount, and getting rid of the mountains of gear that any amphibious 

 operation requires must be a first order of business. All men and supplies are in an exposed 

 position with almost no cover. Troops will encounter very marked differences in trafficability 

 in crossing the fresh beach sand, then rather active dune sand, then vegetation-stabilized older 

 dune sand, until finally solid ground is reached some distance inland. 



Figure 7 is an extension of the same problem, but with a further complexity introduced. 

 If a landing is made here and troops cross the shore dunes, they may find access to the interior 

 barred where stream drainage has been blocked by the dunes and water is ponded. Between the 

 coastal dune belt and dry ground inland there is a moat of marshy, low-lying ground. A photo 

 interpreter without too extensive a background of experience should be able to read these major 

 terrain characteristics from the photograph if he has the proper guidance. We hope to provide 

 him with that guidance by means of a classification which has a rational, scientific, and genetic 

 basis, but one that is cast in empirical rather than theoretical terms so that there will not be 

 a breakdown in communications. 



Frankly, I should have been much happier if we could have turned this problem around 

 the other way and made a number of regional studies from which we could have built a body of 



Figure 7. Coastal dunes, dry region. Dune lakes near 

 Oceano, California. (Spence Air Photo) 



