Definition of Slopes
Although enormous literature has been built on this subject by geomorphologists, engineers, geologists, soil scientists, etc., probably there is no definition of the term ‘slope’. Most land and submarine surfaces have some slope or inclination however small. What are dead level plains also have some slope making drainage of rainfall or precipitation as sheet or channelized flow possible.
However, the study of slope by geomorphologists, etc, generally considers slopes of perceptible inclination such as we see on the mountain ranges, ridges, scarps, edges of plateaus, on the flanks of monadnocks, inselbergs and on the sides of narrow deep-cut valleys.
Although submarine slopes have been investigated by oceanographic surveys and researches, they form a subject of the future so far as their detailed analysis is concerned. Buried under the load of oceanic waters and isolated from the atmosphere their development is mostly different from the slopes on land surfaces.
Thus, in the study of slopes we are concerned with the slopes on land areas. No limit to the degree of slopes appears to have been set by the students of the subject, but mostly it is the slopes which we have summarily mentioned above and which have their application in agriculture, soil characteristics, hydrology, engineering activities, etc.
But it may be mentioned without ambiguity that although most surfaces including practically level cultivated fields have slopes, it is the relatively spectacular slopes that form the subject of slope studies. Practically flat alluvial plains, coastal plains, or very even plateaus fall outside the purview of slope studies.
Factors that Influence the Slope Development
The factors influencing slope development are numerous. Lithology, tectonic characteristics and age of rocks form one set of important factors. Climate and its change constitute another. Tectonic movements and eustatic change of sea level are highly important. Vegetation by providing a protective cover or influencing hydrology or affecting transport of weathered material or otherwise must form another important factor.
The original nature of the surface, e.g., the angle of inclination, its form in respect of concavity, convexity, uniformity, marked knicks or breaks and dislocated surfaces like those along faults will affect the present form of the slopes.
Polycyclic nature of slopes, wherever this is the case, it is definitely an important factor to bear in mind in the correct interpretation of slopes. Variety of factors is indeed bewilderingly large and even in the same environment and microregion there may be baffling variations. “Within a single climatic environment some slopes may recline whereas others retreat parallel”
Thus, Nature is as variable in the details of slopes as in several phenomena. Just as each of some 6,000,000,000 human beings has distinct stature, face, voice, build, attitude, temperament, outlook, character, etc. so is the case with each slope, in whatever site, situation and region, it may be. This makes generalization and quantification about slopes all the more baffling.
This baffling variety must be borne in mind despite all the meticulous quantitative studies and quantification pertaining to slopes.
According to W.M. Davis “landscape is a function of structure, process and stage”. Slope may be described as function of structure, process, stage and tectonics. The structure may be included under the original slope form. The effects of climate, hydrology, glaciation, vegetation, soils, biological factors and probably even tectonics may be included under process. The stage or the time factor in monocyclic or multicyclic slopes is indeed extremely important.