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1.
A comparison of current techniques for measuring elevations in the beach and near-shore zones is presented. Techniques considered
include traditional methods such as ground survey along transects and airborne stereophotogrammetry, and also newer methods
based on remote sensing such as airborne scanning laser altimetry (LiDAR). The approach taken was to identify a representative
group of users of beach elevation data, elicit their requirements regarding these data, then assess how well the different
methods met these requirements on both technical and financial grounds.
Potential users of beach height measurements include those concerned with coastal defence, coastal environmental management
economic exploitation of the intertidal zone, and coastal flood forecasting. Three test areas in the UK were identified covering
a range of such users and also different beach types. A total of 17 basic user requirements were elicited. For each requirement
each method was scored according to the degree to which it could meet the requirement. Total scores were calculated and each
method ranked. This was undertaken for all the requirements together, for a subset relating to survey of narrow beaches, and
for a subset relating to survey of wide beaches. Approximate costs were also established for the top six methods.
Airborne stereophotogrammetry proved to be the best method technically, but was also the most expensive. Ground survey provides
very good technical performance on narrower beaches at moderate cost. Airborne LiDAR can achieve good technical performance
on both narrow and wide beaches at lower cost than ground survey. The satellite-based waterline method was also inexpensive
and gave good results on wide beaches. An overall conclusion is that, while the traditional methods of ground survey and airborne
stereophotogrammetry remain the best for engineering-related surveys requiring high levels of accuracy, airborne LiDAR in
particular looks set to have a significant impact on beach survey for applications for which a vertical accuracy of 20 cm
is acceptable, provided that its technology evolves satisfactorily. 相似文献
2.
Three geomorphic considerations that underpin the design and implementation of realistic and strategic river conservation
and rehabilitation programs that work with the nature are outlined. First, the importance of appreciating the inherent diversity
of river forms and processes is discussed. Second, river dynamics are appraised, framing the contemporary behavioral regime
of a reach in relation to system evolution to explain changes to river character and behavior over time. Third, the trajectory
of a reach is framed in relation to downstream patterns of river types, analyzing landscape connectivity at the catchment
scale to interpret geomorphic river recovery potential. The application of these principles is demonstrated using extensive
catchment-scale analyses of geomorphic river responses to human disturbance in the Bega and Upper Hunter catchments in southeastern
Australia. Differing implications for reach- and catchment-scale rehabilitation planning prompt the imperative that management
practices work with nature rather than strive to ‘fight the site.’ 相似文献
3.
Cycles of storm destruction and rebuilding of human facilities are as much a part of a predictable cycle of shoreline change
as destruction and re-establishment of landforms and wildlife habitat by natural processes. An evaluation of the human-induced
and natural geomorphic responses to three storms in two vulnerable developed areas in New Jersey reveals that storms can have
limited effect in re-establishing a natural coastal resource base of lasting significance. Reconstruction of coastal landscapes
by human action may be more rapid than natural restoration, decreasing the likelihood for geomorphic features to develop based
on natural processes. Reliance on storm processes to create new natural habitat in locations where there is human investment
in buildings and support infrastructure is not realistic unless a proactive stance is taken to include naturally-functioning
characteristics of the coastal system in reconstruction efforts. By striving to control construction of shorefront buildings
to reduce their potential for damage, managers may be taking attention away from the separate but critical issue of ensuring
that post-storm reconstruction effort include the potential for replacing loss of natural geomorphic features and wildlife
habitat. 相似文献
4.
Analysis of shoreline change is often based exclusively upon the littoral cell concept and modelling of hydrodynamic processes.
The Futurecoast study has considered fresh approaches to assessing shoreline evolution, which have been used to provide an
analysis of future long-term evolution for the entire shoreline of England and Wales. This has been based upon an improved
understanding of coastal systems and their behavioural characteristics. The study has included a range of supporting studies,
focussing upon maximizing use of existing information and experience. A number of additional data sets have also been produced.
The integration of leading expertise from different areas of coastal research to collectively consider this information has
been the foundation for the study. The key outputs from this research are: (1) Improved understanding of coastal behaviour;
(2) Assessment of future shoreline evolution; (3) Supporting information and data; (4) Delivery of results on an interactive
CD-ROM. 相似文献
5.
Richard R. Harris 《Environmental management》1988,12(2):219-228
Ten streams in the eastern Sierra Nevada, California, were classified into six geomorphic valley types and sampled to determine environmental and riparian vegetation conditions. The geomorphic valley types were relatively uniform geologically and hydrologically, collectively representing the range of stream environments in the region. There were significant associations between the geomorphic valley types and riparian community composition. These geomorphic-vegetation units are landscape elements which comprise the riparian ecosystems in the region. They differ in their ecological charactersitics and sensitivity to management. The system of landscape elements can be used to classify streams for the purposes of resource inventory, detailed ecological studies, and impact prediction. 相似文献
6.
R. E. Randall 《Journal of Coastal Conservation》2004,10(1):159-168
Coastal vegetated shingle is a rare and declining resource worldwide but is found extensively around the UK coastline. Shingle
sediments b-axes range between 2 mm and 200 mm and occur as fringing beaches, bars, spits, barrier islands and forelands.
Sediment patterns are dependent upon accretion or erosion. With sea-level rise, shingle features tend to move inland. Larger
features may support reservoirs of fresh water but risk becoming saline with sea-level rise. Ranker soils may develop but
are naturally fragile. Vegetated shingle communities are dependent upon substrate stability, moisture and nutrient availability.
Only specialized and some ruderal plants can persist in patterns dependent upon geomorphic history. Coastal defence, agriculture,
public access and control of alien species are important factors in habitat management. Because of its dynamic and unusual
nature coastal vegetated shingle is an important habitat for environmental education. 相似文献
7.
A short outline is given of the floristic composition, structure and distribution of coastal dune vegetation found at Malindi
Bay, Kenya. The area was studied by air photo interpretation and field sampling to determine the relationship of plants to
aeolian features. TWINSPAN classification was used to distinguish geomorphological units on the basis of their species composition.
In this paper, an inventory and first quantitative analysis of vegetation distribution is presented. We identified 174 plant
species from 62 families in the sand dunes and several plant communities are distinguished based on the species content and
the connection with morphological units.Papilionaceae with 18 species andPoaceae with 17 species were the most represented families. A distinct zonal distribution of the plant communities was found.
The most important plant species are the pioneer vegetation consisting ofHalopyrum mucronatum, Ipomoea pescaprae andScaevola plumieri. The woody shrub species which have colonized the established primary dunes and hummock dunes areCordia somaliensis, Pluchea discoridis, Tephrosia purpurea (dunensis). Succulent herbs were identified in the dune slacks and salt marsh that are moist and damp environments. 相似文献
8.
9.
Role of refugia in recovery from disturbances: Modern fragmented and disconnected river systems 总被引:10,自引:0,他引:10
James R. Sedell Gordon H. Reeves F. Richard Hauer Jack A. Stanford Charles P. Hawkins 《Environmental management》1990,14(5):711-724
Habitats or environmental factors that convey spatial and temporal resistance and/or resilience to biotic communities that
have been impacted by biophysical disturbances may be called refugia. Most refugia in rivers are characterized by extensive
coupling of the main channel with adjacent streamside forests, floodplain features, and groundwater. These habitats operate
at different spatial scales, from localized particles, to channel units such as pools and riffles, to reaches and longer sections,
and at the basin level. A spatial hierarchy of different physical components of a drainage network is proposed to provide
a context for different refugia. Examples of refugia operating at different spatial scales, such as pools, large woody debris,
floodplains, below dams, and catchment basins are discussed. We hope that the geomorphic context proposed for examining refugia
habitats will assist in the conservation of pristine areas and attributes of river systems and also allow a better understanding
of rehabilitation needs in rivers that have been extensively altered. 相似文献
10.
Mark M. Brinson 《Environmental management》1988,12(5):655-662
Assessment of cumulative impacts on wetlands can benefit by recognizing three fundamental wetland categories: basin, riverine, and fringe. The geomorphological settings of these categories have relevance for water quality.Basin, or depressional, wetlands are located in headwater areas, and capture runoff from small areas. Thus, they are normally sources of water with low elemental concentration. Although basin wetlands normally possess a high capacity for assimilating nutrients, there may be little opportunity for this to happen if the catchment area is small and little water flows through them.Riverine wetlands, in contrast, interface extensively with uplands. It has been demonstrated that both the capacity and the opportunity for altering water quality are high in riverine wetlands.Fringe wetlands are very small in comparison with the large bodies of water that flush them. Biogeochemical influences tend to be local, rather than having a measurable effect on the larger body of water. Consequently, the function of these wetlands for critical habitat may warrant protection from high nutrient levels and toxins, rather than expecting them to assume an assimilatory role.The relative proportion of these wetland types within a watershed, and their status relative to past impacts can be used to develop strategies for wetland protection. Past impacts on wetlands, however, are not likely to be clearly revealed in water quality records from monitoring studies, either because records are too short or because too many variables other than wetland impacts affect water quality. It is suggested that hydrologic records be used to reconstruct historical hydroperiods in wetlands for comparison with current, altered conditions. Changes in hydroperiod imply changes in wetland function, especially for biogeochemical processes in sediments. Hydroperiod is potentially a more sensitive index of wetland function than surface areas obtained from aerial photographs. Identification of forested wetlands through photointerpretation relies on vegetation that may remain intact for decades after drainage. Finally, the depositional environment of wetlands is a landscape characteristic that has not been carefully evaluated nor fully appreciated. Impacts that reverse depositional tendencies also may accelerate rates of change, causing wetlands to be large net exporters rather than modest net importers. Increases in rates as well as direction can cause stocks of materials, accumulated over centuries in wetland sediments, to be lost within decades, resulting in nutrient loading to downstream aquatic ecosystems. 相似文献