Function and dynamics of woody debris in stream reaches in the central Sierra Nevada, California

1998 ◽  
Vol 55 (8) ◽  
pp. 1807-1820 ◽  
Author(s):  
Neil Berg ◽  
Ann Carlson ◽  
David Azuma
Keyword(s):  
Sierra Nevada ◽  
Deep Water ◽  
Stream Flow ◽  
Woody Debris ◽  
Channel Morphology ◽  
High Flow ◽  
Cover Type ◽  
Sediment Volume ◽  
The Stability ◽  
Channel Type

In 1993, we located, measured, and tagged almost 1700 woody debris pieces on six streams in California’s central Sierra Nevada. The stability, geomorphic function, and use by fish for cover of each piece were recorded. In 1994 and 1995, piece movement was quantified and new debris pieces were measured. In the 60 study reaches, debris was not influential in shaping channel morphology and fish cover. Although woody debris was often associated with habitat units, few pieces deflected flow or contributed to the formation of pools or steps. Fish used deep water as cover more often than debris or any other cover type. Medium-sized debris was, however, used in a greater proportion than its availability to fish. Little sediment was stored by debris, and five large pieces stored 85% of the sediment volume measured. Debris frequency and volume did not differ significantly by channel type. After a low stream flow year (1993–1994), few pieces had moved and few new pieces were identified. After a high-flow season (1994–1995), 31% of the pieces had either moved or were not found and new pieces represented over 5% of the originally surveyed volume of wood.

scholarly journals Applications of High-Resolution Imaging for Open Field Container Nursery Counting

2018 ◽  
Vol 10 (12) ◽  
pp. 2018 ◽  
Author(s):  
Ying She ◽  
Reza Ehsani ◽  
James Robbins ◽  
Josué Nahún Leiva ◽  
Jim Owen
Keyword(s):  
Vegetation Index ◽  
Ground Cover ◽  
Aerial Images ◽  
Support Vector ◽  
Inventory Data ◽  
Cover Type ◽  
Canopy Area ◽  
Resolution Imaging ◽  
Container Nurseries ◽  
The Stability

Frequent inventory data of container nurseries is needed by growers to ensure proper management and marketing strategies. In this paper, inventory data are estimated from aerial images. Since there are thousands of nursery species, it is difficult to find a generic classification algorithm for all cases. In this paper, the development of classification methods was confined to three representative categories: green foliage, yellow foliage, and flowering plants. Vegetation index thresholding and the support vector machine (SVM) were used for classification. Classification accuracies greater than 97% were obtained for each case. Based on the classification results, an algorithm based on canopy area mapping was built for counting. The effects of flight altitude, container spacing, and ground cover type were evaluated. Results showed that container spacing and interaction of container spacing with ground cover type have a significant effect on counting accuracy. To mimic the practical shipping and moving process, incomplete blocks with different voids were created. Results showed that the more plants removed from the block, the higher the accuracy. The developed algorithm was tested on irregular- or regular-shaped plants and plants with and without flowers to test the stability of the algorithm, and accuracies greater than 94% were obtained.

scholarly journals Elements constituent for the design of a riser system in areas deep water and extreme deep water applied for offshore drilling

2020 ◽  
Vol 6 (3) ◽  
pp. 127-144
Author(s):  
Marius STAN ◽  
◽  
Valentin Paul TUDORACHE ◽  
Lazăr AVRAM ◽  
Mohamed Iyad AL NABOULSI ◽  
...  
Keyword(s):  
Working Conditions ◽  
Water Depth ◽  
Deep Water ◽  
Environmental Conditions ◽  
Oil And Gas ◽  
Operational Mode ◽  
Exploration And Exploitation ◽  
Offshore Drilling ◽  
The Stability ◽  
Marine Platform

Riser systems are integral components of the offshore developments used to recover oil and gas stored in the reservoirs below the earth’s oceans and seas. These riser systems are used in all facets of the development offshore process including exploration and exploitation wells completion/intervention, and production of the hydrocarbons. Their primary function is to facilitate the safe transportation of material, oil and gases between the seafloor oceans and seas and the marine platform. As the water depth increases, the working conditions of this system becomes challenging due to the complex forces and extreme environmental conditions which are impacting the operational mode as well as the stability. In this paper several aspects concerning riser mechanics and the behaviour of the riser column will be evaluated against different operational situations.

Down-Canyon Afternoon Winds 1

1961 ◽  
Vol 42 (8) ◽  
pp. 527-542 ◽  
Author(s):  
Mark J. Schroeder
Keyword(s):  
Sierra Nevada ◽  
Short Range ◽  
Wildland Fire ◽  
Fire Fighting ◽  
Lower Atmosphere ◽  
San Diego County ◽  
Fire Control ◽  
Early Afternoon ◽  
Early Fall ◽  
The Stability

In east-facing canyons in the coastal mountains of California, the daytime thermal up-canyon winds are frequently replaced, usually in early afternoon, by a moderately strong down-canyon wind. The same type of wind has also been noted in the western foothills of the Sierra Nevada. This shift in the wind to down canyon is important in wildland fire control and has been a factor in some fire-fighting fatalities. Results of a fire-climate survey conducted in northwestern San Diego County to study these winds show that, in the summer and early fall of 1959, winds switched to down canyon in the afternoon on about one-quarter of the days. From the surface records and a few double-theodolite and airplane observations, a diagrammatic model of this phenomenon has been constructed. The stability of the lower atmosphere along the coast was closely related to the occurrence of down-canyon winds in the area studied. The possibility of making short-range predictions exists by using this relationship along with other considerations.

scholarly journals Estimates of Down Woody Materials on Fort A.P. Hill, Virginia

2008 ◽  
Vol 32 (2) ◽  
pp. 53-59 ◽  
Author(s):  
Jason R. Applegate
Keyword(s):  
Coarse Woody Debris ◽  
Forest Inventory ◽  
Forest Cover ◽  
Forest Type ◽  
Wildland Fire ◽  
Woody Debris ◽  
Forest Cover Type ◽  
Cover Type ◽  
Forest Cover Types ◽  
Structure Class

Abstract An inventory of down woody materials (DWM) was conducted on Fort A.P. Hill, Virginia, to develop a baseline of DWM abundance and distribution to assist in wildland fire management. Estimates of DWM are necessary to develop accurate assessments of wildfire hazard, model wildland fire behavior, and establish thresholds for retaining DWM, specifically CWD (coarse woody debris), as a structural component of forest ecosystems. DWM were sampled by forest type and structure class using US Forest Service, Forest Inventory and Analysis (FIA) field procedures. DWM averaged 12–16 tn/ac depending on forest cover type and structure class. Coarse woody debris (CWD) averaged 2.7–13.0 tn/ac depending on forest cover type and structure class. CWD comprised more than 70% of DWM across all forest cover types and structure classes. Fine woody debris (FWD) averaged 0.05–3.2 tn/ac depending on fuel hour class, forest cover type, and structure class. DWM was consistently higher in mature (sawtimber) forests than in young (poletimber) forests across all forest cover types, attributed to an increased CWD component of DWM. The variability associated with DWM suggests that obtaining robust estimates of CWD biomass will require a higher sampling intensity than FWD because of its nonuniform distribution in forest systems. FIA field procedures for tallying and quantifying DWM were practical, efficient, and, subsequently, included as permanent metrics in Fort A.P. Hill's Continuous Forest Inventory program.

Effect of the environment on processing and handling materials at sea

1978 ◽  
Vol 290 (1366) ◽  
pp. 161-177 ◽  
Keyword(s):  
Deep Water ◽  
Seasonal Variations ◽  
Deep Sea ◽  
Weather Conditions ◽  
Floating Structure ◽  
Mining Operations ◽  
Waste Products ◽  
The Stability ◽  
Vast Range ◽  
Significant Factors

Compared with conventional land-based mining and processing operations, the exploitation of minerals from the seabed, particularly in deep water, involves a vast range of new problems in conducting the various stages of mining, transportation, processing and disposal of waste products, in a marine environment. In all such operations the ways in which local sea and weather conditions and their seasonal variations affect the stability of the vehicle, be it ship or other floating structure or submersible from which the operations are being conducted, have to be taken into account. The resulting motion together with vibration generated by propulsion and other machinery are significant factors in the performance and behaviour of equipment and materials during processing, handling and transportation operations at sea. In deep-sea mining operations at depths of 2-5 km the effects of associated pressure, salinity and temperature must also be dealt with. The paper reviews the present state of such knowledge as currently practised in continental-shelf operations, and as proposed in various deep-sea mining operations. Associated research requirements for future mineral exploitation in the deep-sea environment are discussed.

Dynamic Stability of FPSO-Shuttle Systems: An Analytical Procedure and Practical Results

2002 ◽  
Author(s):  
Ge´rson B. Matter ◽  
Joel S. Sales ◽  
Sergio H. Sphaier
Keyword(s):  
Dynamic Stability ◽  
Deep Water ◽  
Dynamic Systems ◽  
Time Domain ◽  
Equilibrium Position ◽  
Analytical Procedure ◽  
Time Domain Analysis ◽  
The Stability ◽  
The Time Domain ◽  
Floating Systems

The paper deals with the dynamics of floating systems (FPSO units) moored in deep water in the presence of currents. The offloading operation is carried out in a tandem arrangement from the FPSO to a Shuttle ship of lesser capacity. According to the classical theory of dynamic systems, a study of the behavior of floating units is performed by determining the equilibrium position and then analyzing the stability around this position. The time domain analysis is also used to compare the results. This procedure is extended to the case of systems in a spread mooring configuration and with turret.

Hydraulic Sytem for Wave Compensation of Deep-Water Exploration Ship

2012 ◽  
Vol 192 ◽  
pp. 201-206
Author(s):  
Zhi Xin Chen ◽  
Shuai Liu
Keyword(s):  
Deep Water ◽  
Structural Parameters ◽  
Dynamic Performance ◽  
Wire Rope ◽  
Transmission System ◽  
Compensation System ◽  
Work Condition ◽  
Extraction Equipment ◽  
The Stability ◽  
Heave Motion

In order to reduce the influence of the bench extraction equipment from the working deep-water exploration ship when it has swing or heave movement by wind and waves, according to the work condition and the structural parameters of 3000m deep-water exploration ship, Pump-controlled type and valve-controlled type hydraulic transmission system for waves compensation of deep-water exploration ship bench extraction equipment was researched through analysing and calculating. Wire rope which drags the bench is maintained appropriate tensioning status using this wave compensation system, when bench downs to the bottom of the sea. This system can bind and release wire rope to compensate for heave motion automatically, in order to keep the stability and security of the deep-water exploration ship before bench loading the bottom. Dynamic performance of wave compensation system is improved through controlling supplementation pressure and the accumulator parameters precisely.

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