Improvement of streams hydro‐geomorphological assessment using LiDAR DEMs     

Pascale M. Biron  Guénolé Choné  Thomas Buffin‐Bélanger  Sylvio Demers  Taylor Olsen 《地球表面变化过程与地形》2013,38(15):1808-1821

Hydro‐geomorphological assessments are an essential component for riverine management plans. They usually require costly and time‐consuming field surveys to characterize the spatial variability of key variables such as flow depth, width, discharge, water surface slope, grain size and unit stream power throughout the river corridor. The objective of this research is to develop automated tools for hydro‐geomorphological assessments using high‐resolution LiDAR digital elevation models (DEMs). More specifically, this paper aims at developing geographic information system (GIS) tools to extract channel slope, width and discharge from 1 m‐resolution LiDAR DEMs to estimate the spatial distribution of unit stream power in two contrasted watersheds in Quebec: a small agricultural stream (Des Fèves River) and a large gravel‐bed river (Matane River). For slope, the centreline extracted from the raw LiDAR DEM was resampled at a coarser resolution using the minimum elevation value. The channel width extraction algorithm progressively increased the centerline from the raw DEM until thresholds of elevation differences and slopes were reached. Based on the comparison with over 4000 differential global positioning system (GPS) measurements of the water surface collected in a 50 km reach of the Matane River, the longitudinal profile and slope estimates extracted from the raw and resampled LiDAR DEMs were in very good agreement with the field measurements (correlation coefficients ranging from 0 · 83 to 0 · 87) and can thus be used to compute stream power. The extracted width also corresponded very well to the channel as seen from ortho‐photos, although the presence of bars in the Matane River increased the level of error in width estimates. The estimated maximum unit stream power spatial patterns corresponded well with field evidence of bank erosion, indicating that LiDAR DEMs can be used with confidence for initial hydro‐geomorphological assessments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Automatic alignment of contemporary vector data and georeferenced historical maps using reinforcement learning     

Weiwei Duan  Yao-Yi Chiang  Stefan Leyk  Johannes H. Uhl  Craig A. Knoblock 《International journal of geographical information science》2020,34(4):824-849

ABSTRACT

With large amounts of digital map archives becoming available, automatically extracting information from scanned historical maps is needed for many domains that require long-term historical geographic data. Convolutional Neural Networks (CNN) are powerful techniques that can be used for extracting locations of geographic features from scanned maps if sufficient representative training data are available. Existing spatial data can provide the approximate locations of corresponding geographic features in historical maps and thus be useful to annotate training data automatically. However, the feature representations, publication date, production scales, and spatial reference systems of contemporary vector data are typically very different from those of historical maps. Hence, such auxiliary data cannot be directly used for annotation of the precise locations of the features of interest in the scanned historical maps. This research introduces an automatic vector-to-raster alignment algorithm based on reinforcement learning to annotate precise locations of geographic features on scanned maps. This paper models the alignment problem using the reinforcement learning framework, which enables informed, efficient searches for matching features without pre-processing steps, such as extracting specific feature signatures (e.g. road intersections). The experimental results show that our algorithm can be applied to various features (roads, water lines, and railroads) and achieve high accuracy.  相似文献   

How Collaborative Governance Practitioners Can Assess the Effectiveness of Collaborative Environmental Governance,While Also Evaluating Their Own Services     

Trevor Robinson  Michael Kern  Rebecca Sero  Craig W. Thomas 《社会与自然资源》2020,33(4):524-537

Abstract

Collaborative governance applied to environmental issues is becoming more common, and evaluation of such efforts can provide useful information for multiple audiences. However, due to a variety of challenges, collaborative governance practitioners rarely evaluate the outcomes of collaboration and their contributions to these efforts. With these challenges in mind, the William D. Ruckelshaus Center designed an evaluation framework that can meet multiple parties’ objectives, be integrated into practitioners’ existing services, and balance flexibility and practicality with rigor and replicability. The Center conducted a pilot of this framework on a collaborative watershed management effort in southeastern Washington State, where the Center had previously assisted with organizational development. The resulting evaluation highlights a variety of social, knowledge-based, and economic outcomes for the collaborative, as well as lessons for practitioners and evaluators of collaborative governance. We suggest that this methodology can be useful for practitioners interested in evaluating similar collaborative efforts.  相似文献   

Cladocera as indicators of trophic state in Irish lakes   总被引：1，自引：0，他引：1  

Guangjie Chen  Catherine Dalton  David Taylor 《Journal of Paleolimnology》2010,44(2):465-481

We examined the impact of lake trophic state on the taxonomic and functional structure of cladoceran communities and the role of nutrient loading in structuring both cladoceran and diatom communities. Surface sediment assemblages from 33 Irish lakes were analysed along a gradient of total phosphorus concentration (TP; 4.0–142.3 μg l⁻¹), using a variety of statistical approaches including ordination, calibration and variance partitioning. Ordination showed that the taxonomic structure of the cladoceran community displayed the strongest response to changes in lake trophic state, among 17 measured environmental variables. Trophic state variables chlorophyll-a and TP explained about 20% of the variance in both cladoceran and diatom assemblages from a set of 31 lakes. Procrustes analysis also showed significant concordance in the structure of cladoceran and diatom communities (P < 0.001). Thus, lake trophic state affects the taxonomic structure of both primary and secondary producers in our study lakes. We also found a significant decrease in relative abundance of taxa associated with both macrophytes and sediments, or sediments only, along the TP gradient (r = −0.49, P = 0.006, n = 30), as well as an increase in the proportion of the planktonic group (r = 0.43, P = 0.017, n = 30). This suggests that cladoceran community structure may also be shaped by lake trophic state indirectly, by affecting habitat properties. We found no relationship between lake trophic state and the relative abundance of each of three cladoceran groups that display different body size. We compared community structure between bottom and top sediment samples in cores from six Irish lakes. Results revealed similar trajectories of nutrient enrichment over time, as well as a strong shift in cladoceran functional structure in most systems. This study confirms that Cladocera remains in lake sediments are reliable indicators of lake trophic state. This study also highlights the fact that taxonomic and functional structure should both be considered to account for the multiple factors that shape cladoceran communities.  相似文献   

Nature of dissolved P regenerated by plankton: implications for the ssPO4 radiobioassay and for the nature of dissolved P     

William D. Taylor 《Aquatic Sciences - Research Across Boundaries》2010,72(1):13-20

Techniques recently developed for measuring P regeneration, particulate P turnover, and PO₄ ³⁻ concentration in lakewater assume that dissolved ³²P (D³²P) released by plankton is PO₄ ³⁻. To test this assumption, I obtained samples of D³²P regenerated from whole plankton communities by labeling the communities with ³²P-PO₄ ³⁻ then blocking re-uptake and transformation of regenerated D³²P with two competitive inhibitors, unlabeled ³¹P-PO₄ ³⁻ and pyrophosphate. Under these conditions, regenerated D³²P accumulated and could be examined by gel chromatography to discern how much of it was ³²P-PO₄ ³⁻ versus higher molecular weight P compounds. I estimated that most or all of the D³²P released was ³²P-PO₄ ³⁻. I also observed that the amount of DP observed on filtration of lakewater depended on the method employed to obtain the filtrate. Therefore, I also separated particulate ³²P from D³²P with dialysis membrane (100,000 MW cutoff) without pressure. There was little DP larger than PO₄ ³⁻ and no DP >5,000 MW in the dialysate, leading me to conclude that DP <100,000 MW was a minor component of both regenerated and total P. I suggest that under P-limited conditions that most dissolved P observed in lakewater filtrates may be intact viruses and cell constituents liberated in the filtration process. These results are mostly congruent with Lean’s (J Fish Res Board Can 30:1525–1536, 1973) model of P-cycling in lake plankton, although the nature of “colloidal P” in Lean’s model should be further investigated.  相似文献   

Environmental cues and seasonal reproduction in a temperate estuary: a case study of Owenia collaris (Annelida: Polychaeta,Oweniidae)     

Tracey I. Smart  Craig M. Young  Richard B. Emlet 《Marine Ecology》2012,33(3):290-301

Coordination of gametogenesis and spawning during restricted breeding seasons increases availability of mates, fertilization rates, and often success of offspring. Orton’s Rule predicts water temperature as the dominant environmental cue for gametogenesis or spawning in temperate invertebrates. Crisp’s Rule predicts that species producing planktotrophic larvae will time their reproduction to ensure optimal nutrition for the larvae. Owenia collaris (Annelida: Oweniidae) is a temperate polychaete that produces planktotrophic larvae that remain in the water column for several weeks. Reproductive phenology and its relationship to the environment were investigated in an estuarine population of O. collaris using field and laboratory studies. Owenia collaris produced mature gametes between March and September each year during the productive season between the spring and fall transitions when day lengths were 12 h or more, alkalinity was 8.1 or higher, and temperature was 11 °C or higher. Gamete production was not related to seasonal changes in salinity or benthic phytoplankton concentrations and gametes were present prior to the spring phytoplankton bloom. In laboratory experiments, production of gametes was influenced somewhat by manipulating day lengths but not adult food. The association with predictable and stable environmental cycles (day length) and a broad spawning season suggest that this species is unlikely to mis-match with larval food availability which would lead to reduced availability of recruits in any given year, supporting Crisp’s Rule. Our data do not support the hypothesis that reproductive timing in this species is driven by access to excess energy required by adults to initiate the production of gametes. Our data also do not support Orton’s premise that temperature is the primary controlling factor of reproduction in this temperate marine invertebrate.  相似文献   

A 140-year record of recent changes in aquatic productivity in a remote,tropical alpine lake in the Rwenzori Mountain National Park,Uganda     

V. N. Panizzo  A. W. Mackay  I. Ssemmanda  R. Taylor  N. Rose  M. J. Leng 《Journal of Paleolimnology》2008,40(1):325-338

Environmental change in many tropical, alpine habitats remains poorly resolved due to an absence of proximate and sustained observations. In the Rwenzori Mountains of East Africa, glaciers have receded rapidly over the last century, and here we assess the impact of this recession through palaeolimnological analyses of a 45 cm sediment core (Buju3) from Lake Bujuku which is closest to the ice-fields and partly supplied by melt water in-flows. ²¹⁰Pb and ¹³⁷Cs suggest that Buju3 has an average sedimentation rate of 2.9 mm year⁻¹ and the base of the core can be dated to 1864 ± 20 years. Contemporary diatom taxa found in the lake are dominated by Tabellaria flocculosa and Synedra spp., but also include Achnanthes minutissima and Fragilaria pinnata. However, the diatom flora for Buju3 is less diverse and dominated by small, tychoplanktonic species of Fragilaria. Over the period associated with glacial recession, organic carbon isotope analysis (δ¹³C) suggests a small but distinct increase in within-lake productivity, which increases in rate since the mid 1970s up to the present day, in line with a shift towards increased algal productivity (as highlighted by C/N ratios). However, the diatom and pollen records appear rather insensitive to changes in glacier recession since the late 19th century.  相似文献   

A global sense of flow?     

Peter Taylor  Michael Hoyler  Kathy Pain  John Harrison 《Area》2008,40(3):413-415

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HydroGeoSphere: A Fully Integrated,Physically Based Hydrological Model   总被引：4，自引：0，他引：4  

Philip Brunner  Craig T. Simmons 《Ground water》2012,50(2):170-176

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GRB 060607A: a gamma-ray burst with bright asynchronous early X-ray and optical emissions     

Houri Ziaeepour  Stephen T. Holland  Patricia T. Boyd  Kim Page  Samantha Oates  Craig B. Markwardt  Peter Mészáros  Neil Gehrels  Francis E. Marshall  Jay Cummings  Mike Goad 《Monthly notices of the Royal Astronomical Society》2008,385(1):453-467

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