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141.
A field investigation conducted on Boulder Creek in Boulder, Colorado evaluated impacts of flood control maintenance activities on flood conveyance, water quality, and fish habitat. Thirty-nine transects were monitored at one control site and two maintenance sites over a period of eight months. Each site was visited on more than 50 occasions in order to characterize pre- and post-maintenance conditions, and to monitor maintenance activities. Measurements along the transects included substrate composition, flow depth, velocity, and elevation. Reach-average values were assigned to variables such as in-stream vegetation, streambank stability, and woody vegetation before and after maintenance. Water temperature, dissolved oxygen, pH, specific conductance, and turbidity were sampled, and habitat suitability indices were developed pre- and post-maintenance for seven indicator fish species. Water quality impacts during maintenance consisted of high turbidity levels (> 400 NTU), which returned to background levels (0.1–15 NTU) overnight, as well as changes in mean temperature and pH. Alteration of physical channel characteristics as a result of maintenance had limited effects on habitat quality for four of seven fish species, but caused improvements in habitat quality for three fish species. The main implications of this study for floodplain management are that: (1) Flood control maintenance practices can be in direct conflict with water quality and fish habitat objectives, and should be carefully designed and implemented by an interdisciplinary team. (2) Physical habitat for some fish species can be improved as well as reduced by maintenance activities. Habitat suitability curves may be useful tools for evaluating limiting factors of the habitat and for identifying opportunities for habitat improvements as part of maintenance. 相似文献
142.
We assessed relationships between the extent to which farmers reported exposure to relevant information and their attitudes
towards, knowledge about, and degree of adoption of riparian management strategies. We also examined associations between
knowledge of, or receipt of, financial assistance for riparian fencing/planting and intentions for and extent of adoption
of this strategy. A mail survey of 718 pastoral farmers in Otago and Southland in New Zealand [294 surveys returned (41%)]
yielded 279 usable questionnaires. Indices were developed to reflect range and frequency of information use and range of practices
adopted. Attitudes were measured using Likert-type responses to 11 statements, and knowledge as a score on a ten-question
true/false test. Positive relationships between information and the three main response variables (attitude, knowledge, and
adoption) were weak but significant and systematic. These associations remained significant when important demographic and
farm characteristics were taken into account. Informed farmers were more likely to report intentions to carry out riparian
fencing or planting within the next year. Farmers who were aware that funding was available were also more likely to state
this intention, independent of information level. The reported extent to which waterways had been fenced to exclude stock
was related to receipt of funding, but not to information level. Financial factors were the most influential barrier preventing
adoption of permanent fencing. Our research shows a positive correlation between the receipt of information and funding and
the adoption of specific riparian management measures. 相似文献
143.
A morphological comparison of narrow,low-gradient streams traversing wetland environments to alluvial streams 总被引:3,自引:0,他引:3
Jurmu MC 《Environmental management》2002,30(6):0831-0856
Twelve morphological features from research on alluvial streams are compared in four narrow, low-gradient wetland streams
located in different geographic regions (Connecticut, Indiana, and Wisconsin, USA). All four reaches differed in morphological
characteristics in five of the features compared (consistent bend width, bend cross-sectional shape, riffle width compared
to pool width, greatest width directly downstream of riffles, and thalweg location), while three reaches differed in two comparisons
(mean radius of curvature to width ratio and axial wavelength to width ratio). The remaining five features compared had at
least one reach where different characteristics existed. This indicates the possibility of varying morphology for streams
traversing wetland areas further supporting the concept that the unique qualities of wetland environments might also influence
the controls on fluvial dynamics and the development of streams. If certain morphological features found in streams traversing
wetland areas differ from current fluvial principles, then these varying features should be incorporated into future wetland
stream design and creation projects. The results warrant further research on other streams traversing wetlands to determine
if streams in these environments contain unique morphology and further investigation of the impact of low-energy fluvial processes
on morphological development. Possible explanations for the morphology deviations in the study streams and some suggestions
for stream design in wetland areas based upon the results and field observations are also presented. 相似文献
144.
Lowe WH 《Environmental management》2002,30(2):225-233
The movement of individuals among populations can be critical in preventing local and landscape-scale species extinctions
in systems exposed to human perturbation. Current understanding of spatial population dynamics in streams is largely limited
to the reach scale and is therefore inadequate to address species response to spatially extensive perturbation. Using model
simulations, I examined species response to perturbation in a drainage composed of multiple, hierarchically arranged stream-patches
connected by in-stream and overland pathways of dispersal. Patch extinction probability, the proportion of initially occupied
patches extinct after 25 years, was highly sensitive to the extent of species occupancy and perturbation within the drainage,
longitudinal species distribution, perturbation decay rate and the covariance pattern of stochastic effects on colonization
and extinction probabilities. Results of these simulations underscore the importance of identifying and preserving source
populations and dispersal routes for stream species in human-impacted landscapes. They also highlight the vulnerability of
headwater specialist taxa to anthropogenic perturbation, and the strong positive effect on species resilience of habitat rehabilitation
when recolonization is possible. Efforts to conserve and manage stream species may be greatly improved by accounting for landscape-scale
spatial population dynamics. 相似文献
145.
Paul L. Cohen Paul R. Saunders William W. Budd Frederick R. Steiner 《Environmental management》1987,11(5):599-605
King County, Washington is part of the rapidly growing Pacific Northwest region. Analysis of past and current federal, state, and county regulations and administation reveals how stream corridors have been protected to date. This article draws on scientific literature and a case study to suggest future management strategies and guidelines for controlling development in King County watersheds. 相似文献
146.
A transient population outbreak of the Siberian larch casebearer, Coleophora sibiricella Flkv. (Lepidoptera, Coleophoridae), in a protective forest strip and its consequences for the host tree species (Larix sibirica Ledeb.) have been studied for the first time. It has been shown that one-time complete defoliation by this pest and the following infestation by xylophagous insects result in tree death, while the productivity of surviving trees decreases significantly. The results of this study indicate that the Siberian larch casebearer is a major phyllophagous pest of larch and that its populations must be monitored by specialists in forest pathology. 相似文献
147.
A methodology is described that allows determination of instream flow requirements for maintenance of riparian trees. Tree-ring
data revealed strong relationships between tree growth and stream flow volume for riparian species at Rush Creek, an alluvial
stream within an arid setting; these relationships allowed development of models that predict growth rates from hydrologic
variables. The models can be used to assess instream flow requirements under the assumption that certain levels of growth
are necessary to maintain the population. There is a critical need for development and use of instream flow methodologies
for riparian vegetation, since present methodologies focus on needs of aquatic animals (e.g., fish) and may underestimate
needs of the entire riparian ecosystem. 相似文献
148.
149.
Dye tracers have been used in Oregon in the Collection of hydrologic data on 2,350 miles of stream channels in the Long Tom, Umpqua, Willmette, and John Day River basins, and in the Carmen-Smith power tunnel. These investigations demonstrated the usefulness, of dye tracers for determining: (1) estimates of traveltimes and travel rates of water, (2) discharge where standard methods of measuring are not applicable, and (3) dispersion characteristics of streams. Illustrations are used to present the results of time-of-travel studies in simple, concise, and readily interpreted form. 相似文献
150.
Recreational use of streams in the Great Smoky Mountains National Park has increased remarkably during recent years. To better manage the stream resource for visitor needs and at the same time preserve it for future generations, a user study was initiated in 1978. Use patterns, both spatial and temporal, and possible accompanying ecological impacts at three streams were investigated. Sampling was conducted at several sites per stream. The findings indicated that use was concentrated during afternoons and at certain streams and study sites. In addition, different types of users partitioned the streams according to stream morphology (form or structure of pools, riffles, etc.). Major impacts observed were soil compaction and erosion along the streambanks and physical disturbance of the stream bottoms by moving and placing stones to construct dams and raceways. 相似文献