Geography Reference
In-Depth Information
2
mapping potentially hazardous zones within
the selected areas;
3
Minimise erosion on areas that are disturbed
by road construction by a variety of practices
designed to reduce erosion.
3
giving advice on the beneficial use of topography
and surface materials in planning specific traffic
routes and subdivision street layouts;
4
Minimise the off-site impacts of erosion.
4
providing advice on site slope stability and
erosion control works;
ENGINEERING PROBLEMS IN KARST
TERRAIN
5
analysing weathering problems likely to affect
foundations and building materials;
6
dealing with post-construction problems such
as urban stream channel maintenance, causes
of damage by hazards and the monitoring of
geomorphological change.
Soluble rocks have subsurface conditions that pose
problems that are particularly acute in the limestone
areas of Southeast Asia (Box 9.2) and the Caribbean,
including Florida, where cave systems below
ground developed during low Pleistocene sea levels.
In Florida, many cases of subsidence due to sinkhole
collapse have involved law suits in which
geomorphologists have acted as expert witnesses.
Knowledge of the subsurface, of past and present
geomorphic processes, is essential if fair judgements
are to be obtained and future problems avoided.The
key role here for applied geography is to assist
people to 'know the ground they build upon'.
GEOTECHNICAL MEASURE TO
MINIMISE IMPACTS
Geomorphological mapping, developed by
geographers, helps to designate areas of potential
slope instability and land suitability for different
types of construction. Applications range from
building control in Hong Kong, to the planning
of developments at Suez City, Egypt, and
earthquake hazard zonation in San Francisco.
Mapping also assists in assessing multiple hazards,
such as landsliding, flooding and debris flows.
Erosion control guidelines suggest that
construction should be carried out in phases to
avoid disturbing too much of the land at any one
time. No unnecessary clearing should be
undertaken. Immediately below any cleared area,
detention ponds should be constructed to retain
any sediment washed off the site and to hold back
stormwater runoff so that peak discharges in
streams below are not increased.
Particular attention should be paid to the
design of construction roads, and later of
permanent roads. Road design should be
governed by four basic principles:
CONCLUSIONS: TASKS FOR APPLIED
PHYSICAL GEOGRAPHY IN THE
URBAN ENVIRONMENT
Urban areas continue to grow, and within them
land use intensifies. The crowding, consumption
and congestion leads to increasing emissions and
waste, greater vulnerability of the city's people and
more and more significance for the quality of
urban management. The risks associated with
waste disposal and the legacies of past industrial
activity, the opportunity to apply biogeographical
principles in planning urban nature conservation,
and the issues of wildlife and pests within the city
are too complex to be dealt with here, but they
are all part of the urban ecosystem, part of the daily
lives of most of the world's people.
To avoid risks to health, lifestyles and
commerce, good information on the state of urban
areas is needed. On the one hand, work towards
making cities more sustainable and more
environmentally friendly, particularly through Local
Agenda 21, is using indicators of the state of the city.
1
Minimise the amount of disturbance caused
by road construction by (a) controlling the
total mileage of roads; and (b) reducing the
area of disturbance on the roads that are built.
2
Avoid construction in areas of high erosion
hazard.
