say that a line on the face of the earth 

 is the mean high water line, which car- 

 ries an implication of knowledge of own- 

 ership, one is going to get oneself in 

 trouble with photography because it will 

 not work in every case. 



Scale of photography is important; 

 one must be experienced in considering 

 the scale on photography. Satellite im- 

 agery is often at a scale of 1:250,000. 

 The U.S. Geological Survey is planning 

 to develop quad sheets that are 1:10,000 

 when the United States fully adopts met- 

 ric. This 1:10,000 is low level photo- 

 graphy and there are a number of things 

 one can resolve in wetlands using such a 

 scale. 



Analysis of aerial photos of water 

 at the mouth of a stream will reveal 

 patterns about the currents on an ebb or 

 flood tide. The photos also document 

 the conditions of the banks, bare spots, 

 little hammocks, etc. With photography 

 of the scale 1:10,000, we are able to 

 get close to the face of the earth. 



Suppose that instead of looking at 

 1:10,000 scale photography one wants to 

 get a little closer because one is in- 

 terested in more detailed information. 

 One would then need to consider three 

 principal scales: 1:10,000, 1:5,000, and 

 1:2,500. With the latter scale one can 

 actually see dead plant materials on the 

 color IR photos. The bright red patches 

 along the streams may be saltmarsh cord- 

 grass that grows up to 3 m (10 ft) high 

 in summer. One can see some differences 

 in patterning, color and texture of the 

 water, indicating some differences in 

 current, detritus concentration and tur- 

 bidity. 



There is a variety of applications 

 for which one can use quality, color IR 

 aerial photography. 



Another item I was requested to 

 discuss was ditching and diking as they 

 relate to habitat creation. All have 

 been involved with ditching and diking 

 since many have made wildlife impound- 

 ments. Such activities create a landing 

 area for geese and ducks and have some 

 effects on mosquito control. Mosquito 

 control has had a significant impact on 

 the wetlands. Bourn and Cottam (1950) 

 studied mosquito control diking and 

 ditches of marshes around the Delaware 

 Bay. 



What does ditching do in wetlands? 

 It obviously reduces the water level. 

 That is one of the objectives of creat- 

 ing a ditch, i.e, to drain the wetlands. 

 One may want to reduce the water level 

 because of the mosquito, or maybe be- 

 cause in WPA times ditching provided oc- 

 cupational therapy. But what does this 

 reduction in water level cause, at least 

 in the marshes in the more northern lat- 

 itudes? It drains the peat; it lowers 

 the standing water level in the wet- 

 lands; and it can cause an oxidation of 

 the peat. 



Some of the wetland plants we have 

 discussed over the last few days have 

 different tolerances to salt; thus, re- 

 ductions in water level can cause inva- 

 sion of upland plant species further out 

 into what used to be a salt marsh. The 

 fact that the water level is lower, or 

 drains off quicker, or does not stand 

 there as long, will favor the invasion 

 of a number of the upland species of 

 plants. A ditch reduces the number of 

 hectares of vegetated wetland. Even 

 though each ditch may only be 46 to 

 61 cm (18 to 24 inches) wide, a vast 

 area soon is occupied with bare mud sur- 

 faces and open ditches. A ditch can re- 

 duce the area of marsh by about 30%. 



Another problem with ditching is 

 the creation of cat clays. How does 

 ditching result in cat clay problems? 

 Each little scoopful of soil that is ex- 

 cavated from the wetland during ditch 

 construction is placed on the surface of 

 the marsh. Anaerobic material that used 

 to be under the surface goes through nu- 

 merous oxidation steps and ends up as a 

 cat clay. Each one of those little clus- 

 ters of highly acidic material will not 

 serve as a substrate for any vegetation 

 for a number of years. 



It is bad enough that each of the 

 deposits of cat clay does not support 

 plants, but there is also a little halo 

 around it because, as rain falls, the 

 acidic material is leached out and the 

 plants are killed around dredged mate- 

 rial. In some of the Delaware marshes, 

 15 yr passed before plants started grow- 

 ing on such spoil. Because the result- 

 ant elevation of each pile of excavat- 

 ed marsh material was 0.3 to 0.5 m (1 

 to 1.6 ft) above the original eleva- 

 tion of the marsh, the cat clay was not 



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