applied geomorphology

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applied geomorphology Geomorphology has traditionally focused on the study of landforms and on the processes involved in their formation. Applied geomorphology is the practical application of this study to a range of environmental issues, both in terms of current problems and of future prediction. Applied geomorphology provides a strategic tool for informed decision-making in public policy development and in environmental resource management. Key areas of application include specific environmental settings, such as the coastal zone or dryland environments; the impacts of land use and management practice on Earth surface processes; and areas susceptible to natural hazards. Examples of these areas of applied geomorphology are outlined below.

Over 60 per cent of the world's population live in the coastal zone in environments ranging from coral atolls, reclaimed or natural wetlands, dune-backed beaches, and barrier islands to cliff tops. Settlements under threat from coastal erosion and flooding from storm events, sea surges, and rising sea level lobby for protective engineering measures to prevent loss of property, livelihood, and life. Geomorphology has several applications in settings of this type. An understanding of coastal landforms and the processes acting upon them can be used to map areas at risk from cliff failure, beach erosion, and flooding. This approach is of interest to potential developers and the insurance industry and is an important tool in environmental impact assessment (EIA). An understanding of the geomorphology of the coastal zone can also be used to predict the effects of modifying the coastal system. The installation of groynes, breakwaters, or protective sea walls has knock-on effects on the natural circulation of water and sediment in the near-shore environment. Artificially stabilizing cliffs to prevent erosion may seem the obvious solution for cliff-top dwellers, but a geomorphological evaluation might predict that this approach could starve beaches of the sediment provided by natural cliff fall, with a consequent impact on longshore drift of sediment, and would relocate the focus of erosion further along the coast. The nature of the problem may thus change from cliff failure at one site to beach erosion and subsequent flooding at another. An understanding of the nature and complexity of coastal dynamics is thus an essential component of a coastal-zone management strategy and is important in predicting the future effects on coastal landforms of a rise in sea level.

River-management strategies for flood alleviation have often adopted engineering solutions concentrated in particular river reaches, which are usually in areas of urban development. Reach-specific intervention measures include lining the natural channel with concrete to prevent erosion and bank instability, channel straightening to force flood water to flow rapidly through particular reaches, and flow-control structures such as sluice gates and reservoirs to control water level. These artificial measures are not always successful in preventing flooding and erosion within the river catchment, and natural sections further downstream may be overwhelmed by the river at peak flood. The engineered reaches of rivers often become a sterile landscape because fast-flowing water in a concrete-lined channel, with minimal variation in water depth and channel cross-section, provides a poor habitat for wetland flora and fauna. Geomorphology has been applied to ‘river restoration’ to recreate an integrated river management strategy within artificially created river systems, maximizing biodiversity while controlling river-flow conditions. Applied geomorphology uses a holistic approach to river response at a catchment-wide scale; the basis here is an understanding of the relationships between river form and process, sediment transport, and the important role of river-bank (riparian) vegetation.

Certain landscapes have specific properties that impinge on our use and development of the environment. In cold environments, the presence of ground ice leads to problems in construction, communication, and housing. In permafrost zones, the ground is permanently frozen except for the upper layers of the soil, which thaw in the summer. The upper soil, known as the active layer, is subject to repetitive cycles of freezing and thawing, making it geomorphologically active. The ground within the active layer will suffer heaving and deformation, disrupting communications and making road construction impracticable. Applied geomorphology can be used in mapping the active layer and ground ice in areas with differing rocks and sediments. This information is then used to evaluate the problems that are likely to affect these areas. Ground heaving depends on the depth of the active layer and the type of sediment present; fine-grained silts present more of a problem than gravels. Additional problems in permafrost areas, as, for example, in some regions of Alaska, occur where structures have suffered dramatic subsidence as a result of heating in buildings. Without appropriate insulation, heat radiates downwards from the building into the ground, thaws the underlying ice, and increases the depth of the active layer, thus effectively changing the structure of the soil. Applied geomorphology is consequently essential in land-use planning and site evaluation, in order to recognize such potential problems as land subsidence, slope instability, invasion of windblown sand, and impacts on natural drainage systems.

Land used for agricultural production may suffer from degradation and desertification as a result of soil erosion, landsliding, and over-extraction of water for irrigation. Much agricultural practice focuses on maximizing yield and profit, often using techniques that can be detrimental to the environment, both in the short and the long term. Applied geomorphology uses an understanding of the relationships between surface conditions, climate, vegetation, and soil erosion to advise farmers and politicians on how to improve land management for sustainable use of land and water resources.

Natural hazards such as volcanic eruptions, earthquakes, and mudflows present a significant risk to the population of the surrounding area. Geomorphological mapping can be used to assess the present condition of the landscape and provide a hazard map. The expression of a disaster may result in one settlement having significantly different risk assessment. For example, a volcanic eruption may pose a threat from volcanic ash and lava flows, pyroclastic flows, and bombardment from superheated volcanic bombs or associated hazards such as mudflows, depending on topography, soil cover, type of eruption, and predominant wind direction. This application of geomorphological analysis is of significant interest to the emergency services and the insurance industry.

Applied geomorphology can be used in modelling change to landforms and surface processes. This can include change from human impact on the environment to future prediction of climate change, from short-term El Niño and tropical storm events to longer-term change resulting from greenhouse warming and rising sea levels. In this way, applied geomorphology has a key role in managing the environment to minimize potential degradation of land, water, and natural resources.

Michéle L. Clarke

Bibliography

Cooke, R. U. and and Doornkamp, J. C. (1990) Geomorphology in environmental management (2nd edn). Oxford University Press.

geomorphology, applied see applied geomorphology