Environmental Engineering Reference
Ruggedness Index (RI)
Ruggedness Index describes the complexity of the topography and the roughness of
the terrain. The ruggedness indicates the degree of dissection of a region where
drainage has also been taken as an important parameter. Chorley ( 1962 ) has devised
the formula of ruggedness index as:
ReliefM Drainge density km km
This index is being widely used by the earth scientists in connection with the mor-
phological studies of terrain and it leads to better understanding of the surface configu-
ration evolved under complex geomorphic processes. Actually, it is more than
development of slope or dissection index as it incorporates a number of determinant
factors related to the development of landforms. This index reflects the combined effects
of evolutionary rhythmic processes in the development of relief (Mukhopadhyay 1984 ).
Roughness index follows the same trend and indicates a close relationship with
other morphometric attributes like relative relief, slope and dissection index
(Mukhopadhyay 1973 , 1979 ).
Ruggedness index value has been generated using 1 km 2 grid like other morpho-
metric parameters and isolines are drawn for the whole region. Ruggedness index of
the study area is divided into three categories with the help of isolines. The zones
are <0.0078, 0.0078-0.0157 and >0.0157. Minimum ruggedness value is distributed
over maximum study area and it covers 99 % of the total area. 0.0078-0.0157 rug-
gedness value is distributed over the central west and central part of study area and
it covers 0.52 % of total area. More than 0.0157 ruggedness index value is distrib-
uted over central part of the study area and it covers 0.33 % area of land only
(Fig. 2 ). With the low ruggedness index value, minimum effort is needed to manage
surface water which can make the area a good agricultural region.
Relative Relief (RR)
Relative relief is one of the various methods evolved to measure the average slope.
The term was invented and used by Smith ( 1935 ) to ascertain the amplitude of avail-
able relief to relate the altitude of the highest and the lowest points of any particular
area. The study of relative relief depicts the relief of an area in relation to the sur-
rounding areas. The relative relief map gives a clear conception of the nature and
amount of the slope of the area under study.
Relative relief is one of the methods to depict the local relief of any part of
the earth's surface. The study area is having less drainage development and it