Chapter 22
Applied geomorphology in tropical regions
1. Introduction
Tropical zones embrace a great variety of landforms and ecosystems that include
important resources, although they also bear numerous hazards (Reading et al., 1995).
Tropical climates control the life and economic activity of people at a higher level than in
middle latitude climates. In the last 50 years a great demographic explosion has taken
place in tropical regions. At present some 2400 million inhabitants live in these areas,
representing some 45% of the world's population. About 60% live in southern and eastern
Asia. Many of these nations are developing countries with a mainly agricultural
subsistence economy (McGregor and Nieuwolt, 1998). The need for food has led to
agricultural extension and intensification, together with an increase in deforestation
practices. All this has resulted in an increase of soil erosion (Figure 22.1), flooding and
mass movement hazards. These circumstances make it necessary to apply soil
conservation practices (Douglas and Spencer, 1982).
The thick regoliths developed in the humid tropics have been studied in detail due to
their implications for engineering activities (Lovegrove and Fookes, 1972). They have a
varying depth, structure, and mineralogical composition, and abrupt changes are common
within the regolith (Douglas, 1986). All these variations considerably complicate
engineering works.
Humid tropical areas include numerous mineral, hydrocarbon, forest, and agricultural
resources whose exploitations affect different geomorphic processes, usually by triggering
or accelerating their activity. Furthermore, many areas are located on tectonically active
zones and hence can be affected by earthquakes and tsunamis. Volcanic hazards are also
very important, mainly the explosive type, with the emission of burning clouds, ash falls,
and generation of lahars. Finally, hazards with possibly the highest occurrence are those
associated with tropical cyclones, with strong destructive winds, floods, and slides related
to the cyclonic rains, as well as onshore storm surges caused by wind and atmospheric
pressure changes. An example of many of these hazards is represented by the great human
and material losses produced by the Mitch hurricane in Nicaragua and Honduras at the end
of October and beginning of November 1998.
2. Regolith characteristics. Some implications for engineering geology
A wide variety of rocks outcrop in these areas, although granites and other chemically
resistant quartz-rich rocks are among the more abundant in outcrop. For this reason, most
researchers have focused their studies on rocks of granitic compositions. After rock
Applied geomorphology in tropical regions
1. Introduction
Tropical zones embrace a great variety of landforms and ecosystems that include
important resources, although they also bear numerous hazards (Reading et al., 1995).
Tropical climates control the life and economic activity of people at a higher level than in
middle latitude climates. In the last 50 years a great demographic explosion has taken
place in tropical regions. At present some 2400 million inhabitants live in these areas,
representing some 45% of the world's population. About 60% live in southern and eastern
Asia. Many of these nations are developing countries with a mainly agricultural
subsistence economy (McGregor and Nieuwolt, 1998). The need for food has led to
agricultural extension and intensification, together with an increase in deforestation
practices. All this has resulted in an increase of soil erosion (Figure 22.1), flooding and
mass movement hazards. These circumstances make it necessary to apply soil
conservation practices (Douglas and Spencer, 1982).
The thick regoliths developed in the humid tropics have been studied in detail due to
their implications for engineering activities (Lovegrove and Fookes, 1972). They have a
varying depth, structure, and mineralogical composition, and abrupt changes are common
within the regolith (Douglas, 1986). All these variations considerably complicate
engineering works.
Humid tropical areas include numerous mineral, hydrocarbon, forest, and agricultural
resources whose exploitations affect different geomorphic processes, usually by triggering
or accelerating their activity. Furthermore, many areas are located on tectonically active
zones and hence can be affected by earthquakes and tsunamis. Volcanic hazards are also
very important, mainly the explosive type, with the emission of burning clouds, ash falls,
and generation of lahars. Finally, hazards with possibly the highest occurrence are those
associated with tropical cyclones, with strong destructive winds, floods, and slides related
to the cyclonic rains, as well as onshore storm surges caused by wind and atmospheric
pressure changes. An example of many of these hazards is represented by the great human
and material losses produced by the Mitch hurricane in Nicaragua and Honduras at the end
of October and beginning of November 1998.
2. Regolith characteristics. Some implications for engineering geology
A wide variety of rocks outcrop in these areas, although granites and other chemically
resistant quartz-rich rocks are among the more abundant in outcrop. For this reason, most
researchers have focused their studies on rocks of granitic compositions. After rock