Nothing can entirely replace careful field observations in the study of a geomorphic problem, but numerous aid can add to their effectiveness s, reduce the amount of field work for many problems, make possible a more effective planning of the field program, and add support to the conclusions drawn. These aids are what may be called the "tools" of the geomorphologist, although their use is by no means restricted to him. Topographic maps, geologic maps, block diagrams, aerial photographs, soil map, and climatic data are the most commonly used tools in geomorphic studies.

1. Nothing can entirely replace careful field observations in the study of a geomorphic problem,
but numerous aid can add to their effectiveness s, reduce the amount of field work for many problems,
make possible a more effective planning of the field program, and add support to the conclusions
drawn. These aids are what may be called the "tools" of the geomorphologist, although their use is by
no means restricted to him. Topographic maps, geologic maps, block diagrams, aerial photographs,
soil map, and climatic data are the most commonly used tools in geomorphic studies.
1. TOPOGRAPHIC MAPS
• Unless it be the aerial photograph, there is no single tool that has as much usefulness to a
geomorphologist as a topographic map. To a large degree topographic maps and aerial
photographs are complementary to each other; for some purpose one may be more useful, and
for other purposes the other.
• The great advantage of a topographic map is that, besides being three-dimensional, it gives
quantitative information both as to form and altitude. It usually shows regional relation hips
better than any other method of representation.
• It is important in using a topographic map that we early become aware of its quality. Many of
the older maps represent topography poorly. They were made when the drawing of contours
was a matter of personal judgment and interpretation and when topographic sketching was an
art rather than a science.
• The application of aerial photography to topographic map making ha removed a great deal of
the personal equation from the making of contour maps. comparison of old maps with new
ones of the same areas made with the aid of aerial photographs brings out strikingly the
increased accuracy of topographic mapping since about 1925.
Contour interval.
▪ The contour interval is determined largely by the map scale, the amount of relief to be shown,
and how many altitudes have been determined in the map area.
▪ A small contour interval permits the showing of great topographic detail.
▪ Most topographic maps are made with a 10 foot or larger contour interval; this means that some
of the lesser features of the topography will not be shown. Such features as low sand dunes on
an outwash plain or shallow depressions on a pitted outwash plain or sinkhole plain may be
missed entirely if the contour interval is greater than the height of the dunes or the depth of the
depressions.
▪ Many details of floodplain, deltas, and similar low-relief features can be shown effectively only
if the contour interval is as little as 1 or 2 feet.
USES OF TOPOGRAPHIC MAPS
▪ In the following discussion it is assumed that the student can read topographic maps and
interpret the basic information on them. A keen appreciation of individual geomorphic forms
and landscape assemblage is fundamental to a proper interpretation of topographic maps. Forms
that appear alike superficially often may be differentiated if we take into consideration their
relationships to other features on the map.
▪ In addition to thorough study of a map for distinctive geomorphic forms, particular attention
should be given to drainage patterns since they commonly give a clue to the geologic structure
and geomorphic hi tory of the area.
GL-March-2020 Geomorphology
Q U A R T Z – E C I E S Nikhil V. Sherekar
Tools of Geomorphologist

2. ▪ Keeping in mind that dendritic drainage patterns are the "normal" one, any structures where
alternating bands of weak and strong rock are present; rectangular patterns may indicate joint
or fault control upon drainage; radial and annular patterns develop on such features as volcanic
cones, monadnocks, or some type of domal structure; a centripetal pattern may mark structural
or topographic basins or domes with an inversion of topography; and a barbed pattern should
at once suggest the possibility of stream piracy.
▪ Any abrupt changes to surface slopes, stream gradients or courses, as well as types of land
forms, should be considered as possible reflections of varying lithology or structure.
Differences in drainage texture may also provide clues to changes in types of underlying
geologic materials.
▪ Ability to interpret topographic maps accurately can be acquired only through painstaking
attention to map details, combined with a thorough appreciation of the distinctive
characteristics of the many types of terrains.
▪ It is not the primary purpose of this section, however, to explain how to interpret topographic
maps, for usually this can be done better through laboratory or field study of maps. Rather, it is
our purpose to discuss some uses that may be made of them and techniques that can be applied
to their interpretation which may be unfamiliar to the reader marked departure from them
should be carefully considered.
▪ Dendritic patterns reflect homogeneity of lithology or near horizontality of beds; trellis patterns
suggest truncated, folded beds, steeply dipping beds, or possibly faulted.
2. GEOLOGIC MAPS
• The uses of geologic and structural maps in geomorphic studies are so self-evident that they
require little discussion.
• A geologic map suggests the nature of underlying materials and is extremely useful in
determining whether geomorphic features reflect control by lithology and structure or bear
more the imprint of geomorphic processes and history.
• It is almost impossible to separate geomorphic from geologic studies, at least if they have
regional significance.
• Unfortunately, geologic mapping has not kept pace with topographic mapping, and the chances
are more than even that there will be no geologic map of any given area, for, as late as 1946,
less than 10% of the United States had been mapped geologically on a scale as large as 1 inch
to the mile.
• Upon undertaking a geomorphic study of an area unfamiliar to the investigator, one of the first
steps should be to find out whether the geology of the region has been napped.
• The ideal situation is to have available a geologic map, a topographic map, and aerial
photographs of an area, but this is rarely encountered.
• A geologic map, if available, likely to be on a scale considerably less than that of the photos,
but even under the e condition it may be of great value in interpreting the detail of the
topography as shown on the photographs and topographic map.
• With a knowledge of what the geology is, one is forewarned as to what to expect on the
topographic map or photos and thus knows where to look for significant change in topography
as related to geologic variations; sometimes even minor tonal variations on the photographs
come to have real significance.

3. 3. BLOCK DIAGRAMS
• A block diagram is not so much a tool which may be utilized in studying a geomorphic problem
as it is a technique which may be utilized to show effectively results of a study.
• Block diagrams are usually drawn in either one-point or two point perspective, but sometimes
they are drawn in more simplified forms, not in true perspective, which for some purposes are
fairly satisfactory.
• During World War II significant progress was made by the Military Geology Unit of the United
States Geological Survey through the development of two machines for the projecting of
contours so that diagrams could be made showing how a terrain would appear from various
angles.
• A block diagram is an exceedingly valuable illustrative tool when used with proper appreciation
of its limitations. Its chief advantage is that it is diagrammatic and three dimensional and hence
can be made to emphasize pertinent feature and omit irrelevant ones which may obscure the
broader picture.
• A block diagram is easily understood and usually requires little explanation. Its chief
disadvantage is that it is not quantitative and its construction requires a skill and an artistry that
may be lacking, though they can be developed.
• Sometimes block diagrams are made so diagrammatic that they do not show features in their
true relationships and thus give an impression of topography that does not coincide with what
is seen in the field.
• Somewhat similar in purpose to block diagrams are physiographic maps or what have also been
called morphographic or land form maps (Raisz, 1948). They grew out of block diagrams but
differ from them in that they are usually drawn on a small scale.
• Topography is shown by means of hachures and conventionalized symbols. The first major
physiographic map was Lobeck's " Physiographic Diagram of the United States," which
appeared in 1921. Raisz also published in 1939 a physiographic map of the United State entitled
"Landforms of the United States."
4. AERIAL PHOTOGRAPHS
• Probably the most significant geomorphic tool that has become available during the present
century is the aerial photograph.
• A geomorphologist who does not understand at least the basic principles of airialphoto
interpretation is greatly handicapped. What has come to be called photogeology (Rea, 194J)
deals particularly with the geologic interpretation of aerial photographs.
• The science of photogrammetry, which encompasses most of the manifold uses of aerial
photographs, has already developed into a many-sided and highly technical subject, many
aspects of which are highly mathematical.
• A geomorphologist, however, does not need to be familiar with all the technical aspects of
photogrammetry in order to be able to use aerial photos to advantage.
• A proper interpretation of the geomorphic features which they how are first of all dependent
upon a thorough background in the fundamentals of land-form development and land-form
assemblages.

4. Types of aerial photographs.
Aerial photographs are of three types:
verticals, obliques, and composites.
• Simple vertical photos are taken with a single-lens camera with the optical axis in a vertical or
nearly vertical position. They give a flat picture or plan of the area photographed.
• Oblique photos are taken with the optical axis of the camera inclined to the vertical. If the
optical axis i more nearly in the horizontal than in the vertical, the photo is called a high
oblique: if the optical axis is more nearly vertical than horizontal, it is called a low oblique.
• Composite photos taken with multi lens cameras cover a larger area than those taken with
single-lens cameras.
• Mosaics may be made of a large area by patching together individual verticals or obliques and
may serve to some extent a regional map.
• Verticals are more widely used than obliques in geologic field work, whereas obliques are
particularly valuable for illustrative purpose; for certain types of problems they may also be
useful in field studies.
Advantages and disadvantages of aerial photographs:
• The advantages of aerial photographs are manifold, but they do not eliminate the need for top
graphic maps or field work. They are a supplementary tool which can, when used effectively,
reduce greatly the amount of field work and permit much more effective use of a top graphic
map.
• The biggest advantage of aerial photographs lies in the enormous amount of detail which they
show. Many things are discernible on them which do no how on a topographic map and which
may be overlooked or not visible to a person on the ground because of his limited perspective
or inability to detect all the tonal difference in soil, vegetation, and other features.
• To a beginner, the maze of detail on aerial photographs may be confusing, but practice will
enable him to make fullest use of it. Stereoscopic study of photos is usually necessary to obtain
their maximum usefulness.
• Aerial photographs give a continuity of topographic relief and other features not obtainable on
the ground. Aerial photographs are great timesavers in that they make possible a better planning
of the field approach to a problem. Study of them make possible the laying out of the best
traverse routes and the location of the more likely places where significant geomorphic features
and rock outcrops may be found. Except in heavily wooded areas, it i usually possible to locate
points in the field exactly from an aerial photograph, since individual trees, gullies and other
markers are readily recognizable.
• One indirect advantage of aerial photography is that with them, much more so than with
topographic maps. attention will be given to ecological factors and thereby the user will be led
to see how difference in vegetation and soils may give clues to the geology and topography.
• Aerial photographs. however, have their disadvantages and limitations, and these should be
recognized in order to avoid mistakes or undue optimism regarding their value. In spite of the
great detail which they show, they are not absolutely accurate map.
• A camera lens photographs objects in perspective and hence they are not shown in true positions
with respect to a horizontal plane as may be done on a map. Aside from inaccuracies which
may have resulted from tilt of the plane while the photography was done, there is topographic
distortion resulting from the fact that an aerial photograph is a radial rather than isometric
projection.
• In a radial projection, the distance of any point with respect to the centre of the picture is
proportional to it elevation and thus high point are shown relatively farther from the centre than
lower point. Thus, accurate distances and directions cannot be measured except at the centre of
a photograph.

5. • The third dimension may be obtained through use of a stereoscope, but quantitative values of
elevation are not as readily obtainable as on a topographic map.
• Method have been developed for making elevation determinations directly from photograph
(De jardin, 1950), but these procedures are too technical for the beginner. A person observing
photo stereoscopically must be careful not to get an exaggerated idea of relief. Low hill may
look like mountain under a magnifying stereoscope.
• The exaggeration of relief which comes from stereoscopic viewing may be used to an advantage
in the search for feature of such light relief that they do not show on most topographic map.
Thus, in the study of what may be called the microgeomorphology of an area, an aerial
photograph has decided advantages. Feature as mall as ant hill may stand out distinctly, either
because of the stereoscopic
5. SOIL MAPS: A MUCH-NEGLECTED TOOL
• There are five major factor that influence the development of a soil profile: climate, soil biota,
topography, parent material, and time. The last three are geologic in nature, and hence it
should be evident that soil variations reflect to a considerable degree geologic variation of one
type or another.
• Soil maps made prior to 1920 in general are not particularly useful in geologic field work, but
today remarkably detailed and accurate oil maps are being made from field traverses and
airphoto interpretation. Such oil maps, if properly interpreted, can furnish a great deal of
geologic as well as geomorphic information.
• An understanding of the significance of soil series and catena’s is essential to proper u e of soil
maps. All the members of a soil series were derived from the same type of parent material under
essentially similar topographic condition, and hence can be grouped together as designating a
particular type of geologic material. Usually, however, in converting a soil map into a geologic
map, it is more advantageous to work with soil catena’s than with soil series.
• All the members of a soil catena (Bushnell, 1942) were derived from similar parent material,
but they show notable differences in their profiles because of the varying types of topography
under which each soil type formed.
• Soil catenas thus have both geologic and topographic implication. The first step in converting
a soil map into a geologic map is to group together all member of each mapped catena.
• The next step is to determine the parent material from which each soil catena was derived. Until
one has become familiar with the many soil catena which have been recognized, this will
usually entail field observations.
• When these two steps have been taken, it i a simple matter to make a geologic map from a soil
map. Because each member of a soil catena evolved under slightly different topographic
condition, it will be possible to associate the individual soil types with such varying types of
topography as upland flat, light moderate or steep slopes, depression, or floodplains.
• Although a soil map does not give the quantitative information about topography that a
contoured map doe it does give a general picture of the varying types of terrain present in the
mapped area.
• Soil map do not show directly all topographic forms, but they almost always reflect them, and
their topographic implication are readily grasped. They are particularly valuable in area of
continental glaciation, and in such region, one soon finds that the areas of kames and esker,

6. outwash plain and valley train, ground and end moraine, lacustrine area, and area of wind-
blown and sand loess are readily distinguishable by the different soils developed upon them.
The geologic age of the glacial materials usually is indicated by the particular soil series present.
• Soil maps also may be valuable in bedrock geology except in areas where there are many thin
geologic formations. Under these conditions each geologic formation may not be reflected by
a specific oil type.
• If, for example, several adjacent limestone formations are present, a soil map will show where
the limestone are, but it will seldom b useful in distinguishing a particular limestone formation
unless one possesses some marked mineralogic quality that gives rise to a distinctive soil type.
• Where geologic formation has an appreciable width of outcrop, however, as in a region of
gently dipping formations of considerable thickness, a soil map, when properly interpreted,
becomes a rather good geologic map. For many types of geologic work, a soil map ranks with
a topographic map or aerial photograph in usefulness in mapping areal geology.
6. CLIMATIC MAPS
• Although it is generally recognized that climatic variation has an influence upon the operation
of the geomorphic processes, surprisingly few attempts have been made to correlate the two.
• In many parts of the world this has been impossible because of scarcity or lack of detailed
weather and climatic data, but for considerable area data are available for long enough periods
to give an adequate picture of weather and climatic conditions.
• Many types of geomorphic problems can be studied better if detailed climatic information is
brought to bear upon them. Information on precipitation, including not only the annual amount,
but its seasonal distribution, variability, the percentages which fall as rain or snow, intensity of
rainfall, particularly of the extremely heavy rain , and many other a aspects of the precipitation
may well contribute to a better understanding of problems involving types and rates of erosion.
• Visher (1937, 1945) has emphasized the importance of extreme rainfalls in the problem of
erosion and has shown, for example, that the greater erosional rate in southern Indiana as
compared with northern Indiana is not solely the result of the greater relief in southern Indiana
but is related also in part to greater rainfall there, a greater percentage of rainfall during the
winter months when the protective effects of vegetation are at a minimum, greater frequency of
torrential rain , (fewer day of frozen ground in winter, and other factors that contribute to
maximum erosional effects.)
• Consideration should be given to such temperature factors as average annual temperature,
annual range of temperature, daily range of temperature, number of days with temperatures
above and below freezing, depth of frost penetration, frequency of days with freeze and thaw,
and such other temperature factors as may influence the operation of geomorphic processes
(Visher, 1945) .