DOCSLIB.ORG

Hydrodynamics and Morphodynamics of River Confluences

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Hydrodynamics and Morphodynamics of River Confluences HYDRODYNAMICS AND MORPHODYNAMICS OF RIVER CONFLUENCES Summer school: Day 2 – (29 July 2015) 11:30 – 12:15 (B) Gökçen Bombar Ege University, Turkey 1 A confluence is the meeting of two or more bodies of water. When Rivers Collide: 10 Confluences Around the World (the confluences were selected for their dramatic visual contrast) Confluence of the Confluence of the Green and Colorado Rhone and Arve Rivers Rivers in Canyonlands National Park, in Geneva, Switzerland Confluence of the Jialing and Utah, USA Yangtze Rivers in Chongqing, China http://twistedsifter.com/2012/04/confluences-around-the-world/ 2 River confluences : - fundamental elements of natural drainage networks, - play an important role in regulating the movement of sediment through river systems, - are habitats of high ecological value, - dynamics of mixing controls how tributary inputs of nutrients and food are dispersed within a main river, 3 Terminology Symmetrical Confluence Asymmetrical Confluence Y - Shaped http://3.bp.blogspot.com/_KV-lA7YaO9U/SSGqh- http://twistedsifter.com/2012/04/confluences-around-the-world/ 4EhXI/AAAAAAAAC6o/cwyQO1ZMcws/s1600- h/IMG_7254.JPG Bryan & Kuhn, 2002, Hydraulic conditions in experimental rill confluences and scour in erodible soils. 4 Influential Parameters : tributary channel Qst inner bank Q h sm Bm p-c main channel outer bank post- confluence 5 Influential Parameters : discharge from tributary and main channel, Qt & Qm [discharge ratio, Qr = Qt / Qm ] sediment load, Qst , Qsm sediment characteristics, D50t , D50m , st , sm , rs angle between the two incoming streams and downstream channel junction angle, α, momentum flux ratios, Mr = ( r Qt Vt ) / ( r Qm Vm ) where Q, U, and ρ denote the flow discharge, mean flow velocity and density of water respectively, and the sub-indexes t and m refer to the tributary and main channel, respectively. velocity ratio, Vr = Vt / Vm height of bed discordance, Dz 6 Mosley (1976) An experimental study of channel confluences • Flow patterns and processes in conflences, • Factors that control the scour depths • Equilibrium conditions 7 One of the most important issue, which has been the subject of a large scientific debate, concerns the * presence, and * number, of the secondary flow cells driven by the confluence. Mosley (1976) reported the presence of two counter-rotating helical flow cells downstream of the confluence, generated by the converging flows and separated by a shear layer. 8 Hydrodynamics at open channel confluences Best (1987) Flow dynamics at river channel confluences: Implications for sediment transport and bed morphology tributary channel inner bank 3 1 main 5 post- channel 2 2 4 confluence 6 5 4 outer bank 9 A turbulence feature of particular interest has been the shear layer between two confluent flows. This feature is analogous to the plane mixing layer that develops between interfacial shear flows. Over distance, mixing layers evolve by spreading laterally via vortex pairing. 10 Brown and Roshko (1974) On density effects and large structure in turbulent mixing layers. Mixing Layers: Turbulent Mixing Layers are formed when two dissimilar streams of turbulent fluid travel parallel to each other. Commonly, the streams are initially separated by a thin, low angle splitter plate. Figure shows a shadowgraph image of a mixing layer created by Brown & Roshko (1974). These structures are caused by Kelvin-Helmholtz instability at the junction of the two streams. channel width is 5 cm 11 Winant & Browand (1974) Vortex Pairing: the mechanism of turbulent mixing-layer growth at moderate Reynolds number. Vortex Pairing: Dye was injected between the two streams. • unstable waves grow, • fluid is rolled up, • interact by rolling around each other, and • a single vortical structure was formed. The downstream thickening of the turbulent mixing layer arises through sequential amalgamation of these vortices to form larger vortices. https://www.youtube.com/watch?v=r5xV5Lt1EdI 12 University of Illinois, USA Kaskaskia River - Copper Slough confluence The field site near Champaign, IL ; measurement since 1989. Kaskaskia River flow Copper Slough flow B = 7 m B = 8.5 m D50 = 0.65 mm D50 = 3.5 mm • Kenworthy, S.T. and Rhoads, B.L., 1995. Hydrologic Control of Spatial Patterns of Suspended Sediment Concentration at a Small Stream a = 600 Confluence. Journal of Hydrology, 168, 251-63. • Rhoads, B.L. and Kenworthy, S.T. , 1995. "Flow Copper Slough Structure at an Asymmetrical Stream Confluence." Geomorphology, 11, 273-293. • ....... Kaskaskia River • ....... • ....... The local path of the depth-averaged flow is often skewed in relation to the path of the channel centerline. July 1989 13 The cross-stream velocities consist of velocity components associated with helical motion, if present, and with skewness of the flow path in relation to the channel path. The definition of flow structure in natural rivers is contingent upon the frame of reference in which velocity components are presented. Bathurst, Thorne & Hey (1977) Direct measurements of secondary currents in river bends V : depth averaged velocity vector. Vx and Vy : components of V on stream and cross flow axis. vp and vs : components of the velocity at a particular depth in the flow column that are oriented parallel and orthogonal, respectively, to the V at that vertical. vpy and vsy : projection of vp and vs on cross-stream axis, respectively. 14 vy = vpy + vsy skewed helical flow motion vs vsy vy vx vpy Vy v p V v x Bathurst, Thorne & Hey (1977) Direct measurements of secondary V currents in river bends 15 Rhoads & Kenworthy (1995) Field investigation at an asymmetrical Kaskaskia River flow - Copper Slough flow stream confluence West bank – East bank outer bank – inner bank Main channel - tributary channel At low stage Q = 0.56 m3/s - Q = 0.42 m3/s No sediment transport m t Mr = 0.55 < 1 Mixing interface v y vpy vsy • The mixing interface is positioned near the center of the channel immediately downstream from the confluence. • Weak but surface convergent cells occur on each side of the mixing interface. • The flow from the lateral tributary can not penetrate far into the confluence. • Values of vsy are small 16 Effect of Momentum Ratio on the Shear Layer: Low momentum flux ratios (Mr < 1) indicates a dominan main stream and yield a shear layer close to the inner bank of the main channel, High momentum flux ratios (Mr > 1) lead to a shift of the shear layer towards the outer bank. Lewis, (2014) Rates and patterns of temperature mixing at a small stream confluence under variable incoming flow conditions 17 Bed Discordance: First models of junction dynamics have tended to assume that the confluent channels are of equal depth, a condition that may be found only rarely in natural junctions; more often, the depths of confluent channels are different. The difference in height between the bed levels of the tributary and main channel and is highly influences the hydrodynamics of confluences. This discordance is commonly the result of the bars – due to sediment transport - at the mouth of each confluent channel. Concordant Bed Discordant Bed 18 Biron, Best & Roy (1996), Effects of bed discordance on flow dynamics at open channel confluences a = 30 degree Bt = 8 cm ; Bm = 12 cm ; Bp-c = 15 cm LDA & white dye * Seperation zone: concordant discordant Streak paths of spots of white water-based paint placed on the blue perspex flume door. a) The main channel flow is deflected away from the mouth of the tributary. The streamline curvature is associated with a seperation zone. b) Deflection is negligible 19 * Acceleration zone: The existence of a seperation zone may reduce the available area through which the total discharge must pass, resulting in a flow acceleration zone. At the discordant bed, absence of a flow seperation zone near the bed results in no marked flow acceleration zone near the corner. * Upwelling flow: Velocity vectors in the u-v plane near the tributary wall near the downstream junction corner: a) All the vectors remain parallel to the bed, b) A very strong vertical motion exits immediately downstream from the corner. • Bed discordance clearly generates an upwelling of flow at the downstream junction corner. 20 Effect of sediment feeding from the tributary and the main channel on the equilibrium morphology of a river confluence Experimental Facility sediment feeder of the sediment feeder of the mean channel tributary channel instrument car tributary channel control table main channel 21 Effect of sediment feeding from the tributary and the main channel on the equilibrium morphology of a river confluence CONFLUME Control equipment: Data acquisition: • Tributary sediment feeding. • Water surface levels (ultrasonic sensor). • Movement of instruments in x, y, z, within • Bed topography (mini echo-sounder). specified intervals and speed. • Velocity (UVP and ADV - Vectrino). • Start and end the measurement session. • Camera. 22 Effect of sediment feeding from the tributary and the main channel on the equilibrium morphology of a river confluence Q sm 0.6 0.2 0 Q st 0.5 A1 B1 C1 0.34 A2 B2 C2 0.17 A3 B3 C3 0.08 A5 B5 C5 0 A4 B4 C4 Q sm & Q st (kg/hr)(kg/min) 23 10A5 rep0.60 0.08 2 0 0.3 4 6 0.25 8 10 0.2 12 0.15 14 16 0.1 18 0.05 20 22 0 10010200A5 rep300 0.60400 500 0.08600 700 800 900 Effect of sediment feeding from2 the tributary and the main channel on the equilibrium morphology of a river confluence 1 0.3 4 0 6 0.25 8 10 0.2 12 0.15 14 16 0.1 18 0.05 20 22 A1 0 C5 2 A1 0.60 0.50 10010200A5 rep300 0.60400A5500 0.08 600 700 800
Load more

Recommended publications
  • (P 117-140) Flood Pulse.Qxp
    117 THE FLOOD PULSE CONCEPT: NEW ASPECTS, APPROACHES AND APPLICATIONS - AN UPDATE Junk W.J. Wantzen K.M. Max-Planck-Institute for Limnology, Working Group Tropical Ecology, P.O. Box 165, 24302 Plön, Germany E-mail: [email protected] ABSTRACT The flood pulse concept (FPC), published in 1989, was based on the scientific experience of the authors and published data worldwide. Since then, knowledge on floodplains has increased considerably, creating a large database for testing the predictions of the concept. The FPC has proved to be an integrative approach for studying highly diverse and complex ecological processes in river-floodplain systems; however, the concept has been modified, extended and restricted by several authors. Major advances have been achieved through detailed studies on the effects of hydrology and hydrochemistry, climate, paleoclimate, biogeography, biodi- versity and landscape ecology and also through wetland restoration and sustainable management of flood- plains in different latitudes and continents. Discussions on floodplain ecology and management are greatly influenced by data obtained on flow pulses and connectivity, the Riverine Productivity Model and the Multiple Use Concept. This paper summarizes the predictions of the FPC, evaluates their value in the light of recent data and new concepts and discusses further developments in floodplain theory. 118 The flood pulse concept: New aspects, INTRODUCTION plain, where production and degradation of organic matter also takes place. Rivers and floodplain wetlands are among the most threatened ecosystems. For example, 77 percent These characteristics are reflected for lakes in of the water discharge of the 139 largest river systems the “Seentypenlehre” (Lake typology), elaborated by in North America and Europe is affected by fragmen- Thienemann and Naumann between 1915 and 1935 tation of the river channels by dams and river regula- (e.g.
    [Show full text]
  • Calvin Park Tributary Stream Restoration -- Survey Phase
    Neighborhood Advisory Croydon Creek – Calvin Park Tributary Stream Restoration -- Survey Phase Project Rockville’s Department of Public Works has begun the design of the Croydon Creek – Description: Calvin Park Tributary Stream Restoration project. The city’s consultant, AECOM, will survey the area within Rockville Civic Center Park in the project limits depicted on the back side of this advisory. The survey will identify features including the existing roads, stream, trees, utilities, and topography. Survey work will begin in March and will continue into the spring. Surveyors and engineers with equipment will traverse the area shown on the back of this advisory. Survey stakes may be placed in the ground and trees may be marked with temporary metal tags to assist in identification and inventory. The survey flags do not indicate tree removal. Purpose: The Croydon Creek – Calvin Park Tributary Stream Restoration project was recommended in the 2013 Rock Creek Watershed Assessment as a crucial component to the long-term health of the watershed. The assessment was approved by the Mayor and Council in February 2013, and this project was included in the adopted Fiscal Year 2017 Capital Improvements Program. The project goals are to enhance the watershed through stream restoration, wetland enhancement, reforestation, and the protection of private and public property and infrastructure Location: Croydon Creek within Rockville Civic Center Park and the Calvin Park Tributary from Baltimore Road to Croydon Creek (See the map on the back of this advisory). Timeline: Survey work and preliminary design is anticipated to begin in March and continue through spring. A community meeting will be held this summer to provide additional details of the project.
    [Show full text]
  • Geomorphic Classification of Rivers
    9.36 Geomorphic Classification of Rivers JM Buffington, U.S. Forest Service, Boise, ID, USA DR Montgomery, University of Washington, Seattle, WA, USA Published by Elsevier Inc. 9.36.1 Introduction 730 9.36.2 Purpose of Classification 730 9.36.3 Types of Channel Classification 731 9.36.3.1 Stream Order 731 9.36.3.2 Process Domains 732 9.36.3.3 Channel Pattern 732 9.36.3.4 Channel–Floodplain Interactions 735 9.36.3.5 Bed Material and Mobility 737 9.36.3.6 Channel Units 739 9.36.3.7 Hierarchical Classifications 739 9.36.3.8 Statistical Classifications 745 9.36.4 Use and Compatibility of Channel Classifications 745 9.36.5 The Rise and Fall of Classifications: Why Are Some Channel Classifications More Used Than Others? 747 9.36.6 Future Needs and Directions 753 9.36.6.1 Standardization and Sample Size 753 9.36.6.2 Remote Sensing 754 9.36.7 Conclusion 755 Acknowledgements 756 References 756 Appendix 762 9.36.1 Introduction 9.36.2 Purpose of Classification Over the last several decades, environmental legislation and a A basic tenet in geomorphology is that ‘form implies process.’As growing awareness of historical human disturbance to rivers such, numerous geomorphic classifications have been de- worldwide (Schumm, 1977; Collins et al., 2003; Surian and veloped for landscapes (Davis, 1899), hillslopes (Varnes, 1958), Rinaldi, 2003; Nilsson et al., 2005; Chin, 2006; Walter and and rivers (Section 9.36.3). The form–process paradigm is a Merritts, 2008) have fostered unprecedented collaboration potentially powerful tool for conducting quantitative geo- among scientists, land managers, and stakeholders to better morphic investigations.
    [Show full text]
  • The Arkansas River Flood of June 3-5, 1921
    DEPARTMENT OF THE INTERIOR ALBERT B. FALL, Secretary UNITED STATES GEOLOGICAL SURVEY GEORGE 0ns SMITH, Director Water-Supply Paper 4$7 THE ARKANSAS RIVER FLOOD OF JUNE 3-5, 1921 BY ROBERT FOLLANS^EE AND EDWARD E. JON^S WASHINGTON GOVERNMENT PRINTING OFFICE 1922 i> CONTENTS. .Page. Introduction________________ ___ 5 Acknowledgments ___ __________ 6 Summary of flood losses-__________ _ 6 Progress of flood crest through Arkansas Valley _____________ 8 Topography of Arkansas basin_______________ _________ 9 Cause of flood______________1___________ ______ 11 Principal areas of intense rainfall____ ___ _ 15 Effect of reservoirs on the flood__________________________ 16 Flood flows_______________________________________ 19 Method of determination________________ ______ _ 19 The flood between Canon City and Pueblo_________________ 23 The flood at Pueblo________________________________ 23 General features_____________________________ 23 Arrival of tributary flood crests _______________ 25 Maximum discharge__________________________ 26 Total discharge_____________________________ 27 The flood below Pueblo_____________________________ 30 General features _________ _______________ 30 Tributary streams_____________________________ 31 Fountain Creek____________________________ 31 St. Charles River___________________________ 33 Chico Creek_______________________________ 34 Previous floods i____________________________________ 35 Flood of Indian legend_____________________________ 35 Floods of authentic record__________________________ 36 Maximum discharges
    [Show full text]
  • Amazon River Voyage
    AMAZON RIVER VOYAGE Over the 38 years that International Expeditions has been leading Amazon River cruises, our guests have enjoyed unrivaled access to the Peruvian rainforest’s most pristine areas and the company of the river’s most knowledgeable guides. Your exciting daily excursions include birding at dawn, school visits in local villages and even piranha fishing! Join IE and be transported to the Amazon of your imagination to discover a rainforest that pulsates with an unrivaled diversity of wildlife. Authentic Amazon River Experience Aboard this luxury Amazon River cruise, you’ll create a lifetime of memories: the joy in the eyes of a village child when you visit their school; the enveloping darkness of the jungle; or the awe possible. of floating along narrow streams accompanied by pink dolphins. Drawing on insight from our native Amazon travel guides, Explore with Pioneers in Amazon Travel International Expeditions intentionally varies the villages and International Expeditions pioneered travel to the Peruvian tributaries we visit, ensuring you get the most authentic Amazon, and our nature-focused, small-group expedition travel rainforest tour experience remains the standard for Amazon Voyage expedition cruises. IE not only pioneered travel to this region, we still work with many of the naturalist guides that we helped to train. Ensuring a worry-free and educational journey, these expert local naturalist guides — along with an expedition leader — accompany our Amazon Voyage cruises. Each day, these knowledgeable Amazon River travel guides use their decades of learning and guiding experience to serve as lecturers, field guides and friends as you explore the rainforest.
    [Show full text]
  • Classifying Rivers - Three Stages of River Development
    Classifying Rivers - Three Stages of River Development River Characteristics - Sediment Transport - River Velocity - Terminology The illustrations below represent the 3 general classifications into which rivers are placed according to specific characteristics. These categories are: Youthful, Mature and Old Age. A Rejuvenated River, one with a gradient that is raised by the earth's movement, can be an old age river that returns to a Youthful State, and which repeats the cycle of stages once again. A brief overview of each stage of river development begins after the images. A list of pertinent vocabulary appears at the bottom of this document. You may wish to consult it so that you will be aware of terminology used in the descriptive text that follows. Characteristics found in the 3 Stages of River Development: L. Immoor 2006 Geoteach.com 1 Youthful River: Perhaps the most dynamic of all rivers is a Youthful River. Rafters seeking an exciting ride will surely gravitate towards a young river for their recreational thrills. Characteristically youthful rivers are found at higher elevations, in mountainous areas, where the slope of the land is steeper. Water that flows over such a landscape will flow very fast. Youthful rivers can be a tributary of a larger and older river, hundreds of miles away and, in fact, they may be close to the headwaters (the beginning) of that larger river. Upon observation of a Youthful River, here is what one might see: 1. The river flowing down a steep gradient (slope). 2. The channel is deeper than it is wide and V-shaped due to downcutting rather than lateral (side-to-side) erosion.
    [Show full text]
  • Drainage Patterns
    Drainage Patterns Over time, a stream system achieves a particular drainage pattern to its network of stream channels and tributaries as determined by local geologic factors. Drainage patterns or nets are classified on the basis of their form and texture. Their shape or pattern develops in response to the local topography and Figure 1 Aerial photo illustrating subsurface geology. Drainage channels develop where surface dendritic pattern in Gila County, AZ. runoff is enhanced and earth materials provide the least Courtesy USGS resistance to erosion. The texture is governed by soil infiltration, and the volume of water available in a given period of time to enter the surface. If the soil has only a moderate infiltration capacity and a small amount of precipitation strikes the surface over a given period of time, the water will likely soak in rather than evaporate away. If a large amount of water strikes the surface then more water will evaporate, soaks into the surface, or ponds on level ground. On sloping surfaces this excess water will runoff. Fewer drainage channels will develop where the surface is flat and the soil infiltration is high because the water will soak into the surface. The fewer number of channels, the coarser will be the drainage pattern. Dendritic drainage pattern A dendritic drainage pattern is the most common form and looks like the branching pattern of tree roots. It develops in regions underlain by homogeneous material. That is, the subsurface geology has a similar resistance to weathering so there is no apparent control over the direction the tributaries take.
    [Show full text]
  • Brand New Mississippi Sternwheeler from American Cruise Lines
    Brand New Mississippi Sternwheeler from American Cruise Lines Guilford, CT - American Cruise Lines has announced it is expanding to the Mississippi River system with a brand new sternwheeler, already under construction at Chesapeake Shipbuilding in Salisbury, MD. It plans to operate the new riverboat on routes similar to those formerly run by Delta Queen Steamboat Company, which will include the Mississippi, Ohio, Tennessee, and Cumberland Rivers. Cruising the Mississippi River on a sternwheeler is a true all-American experience that American Cruise Lines is pleased to bring back. The new paddlewheeler will recreate the grandeur of past riverboats while possessing the latest safety, environmental and construction technologies. The ship will have the look of a traditional riverboat along with more amenities, a faster speed, and an unmatched level of comfort. Features include six unique lounges, a library, an elegant dining salon, elevator service to all decks, and the exceptionally large staterooms found on all American Cruise Lines ships. With only 140 passengers, each guest will receive personalized service in the intimate and friendly atmosphere for which American Cruise Lines has become known. The first cruise is a scheduled to depart August 11, 2012 from New Orleans, Louisiana on a 7-night journey up the Mississippi to Memphis, Tennessee. The ship will then begin a series of 7-night cruises travelling as far north as St. Paul, Minnesota while utilizing its remarkable speed to open up new itinerary possibilities. As on all true riverboats, a stage and bow ramp will give the ship access to the many interesting ports without docking facilities.
    [Show full text]
  • The Cedar River
    Since the 1800’s, Iowa rivers have been designated as CEDARCEDAR either meandered or non- RIVERRIVER meandered. Much of the Cedar River Water Trail is lined with public lands and classified as meandered, meaning that BLACK HAWK COUNTY paddlers may access not only BLACK HAWK the river itself but also the COUNTY river bottom and banks along its course. However, north of Washington Park, the river is classified as non-meandered, meaning that the river bed and surrounding land are owned by the adjacent landowners and paddlers should respect their property rights. BLACK HAWK COUNTY THE CEDAR RIVER - WILDNESS AND CIVILIZATION The Cedar River Water Trail offers a unique paddling experience amongst Iowa’s designated water trails. A journey down the 47 miles of the trail features dramatically contrasting settings, with the wildness of forested bottomlands rich with diverse plant, wildlife, and bird species giving way to historic urban environments. Paddlers are offered an opportunity to explore the downtowns of two major Iowa cities before returning again to the river’s pastoral setting. Traversing the county’s widest stream, its landscape, and lore may feel like time travel at times. From prehistoric times into the present, the Silver maples shade a peaceful backwater of the Cedar River Cedar River valley continues to beckon These trees, typical of bottomland hardwood forest, often grow right up to the water’s to paddlers to explore its natural beauty edge. Quiet back channels are “nurseries” for aquatic wildlife and isolated nesting areas for and cultural treasures. birds and wildlife. Red-spotted purple butterfly Bank swallow nest holes Cedar waxwing gathering nest material CEDAR RIVER WATER TRAIL The Cedar River bisects Black Hawk County diagonally as it continues to erode the landform region called the Iowan Surface.
    [Show full text]
  • Community Report
    Community Report Dear Friends, As we refl ect on 2019 so far and look forward to the rest of the Our Mission year, I am thankful for all of those who give their time and talents to make Confl uence Health a place I am proud to be a part of We are dedicated to improving our patients’ every day. Our vision states that Confl uence Health strives “to health by providing safe, high-quality care in become the highest value rural health care system in the nation,” a compassionate and cost-effective manner. About Us and that goal isn’t achieved by accident. Our success is directly impacted by the dedication of our exceptional physicians, nurses, employees, volunteers and leadership teams, who all share a commitment to our patients. Healthy individuals make Our Vision healthy communities, and we understand and embrace the part we play in making that a reality. To become the highest value rural health 4, 000+ employees care system in the nation that improves Additionally, fulfi lling this vision means ensuring the best possible health, quality of life, and is a source of health outcomes at the lowest possible cost, whenever and wherever our patients need care. If we can accomplish that, pride to those who work here. we will uphold our founding principle that a locally controlled, 12 cities directed and integrated health care delivery system best meets the needs of this region. While acknowledging our successes, we understand there is still 12,000 much to do to ensure our community receives the effective and square mile timely care it deserves.
    [Show full text]
  • Holocene Environmental Archaeology of the Yangtze River Valley in China: a Review
    land Review Holocene Environmental Archaeology of the Yangtze River Valley in China: A Review Li Wu 1,2,*, Shuguang Lu 1, Cheng Zhu 3, Chunmei Ma 3, Xiaoling Sun 1, Xiaoxue Li 1, Chenchen Li 1 and Qingchun Guo 4 1 Provincial Key Laboratory of Earth Surface Processes and Regional Response in the Yangtze-Huaihe River Basin, School of Geography and Tourism, Anhui Normal University, Wuhu 241002, China; [email protected] (S.L.); [email protected] (X.S.); [email protected] (X.L.); [email protected] (C.L.) 2 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China 3 School of Geograpy and Ocean Science, Nanjing University, Nanjing 210023, China; [email protected] (C.Z.); [email protected] (C.M.) 4 School of Environment and Planning, Liaocheng University, Liaocheng 252000, China; [email protected] * Correspondence: [email protected] Abstract: The Yangtze River Valley is an important economic region and one of the cradles of human civilization. It is also the site of frequent floods, droughts, and other natural disasters. Conducting Holocene environmental archaeology research in this region is of great importance when studying the evolution of the relationship between humans and the environment and the interactive effects humans had on the environment from 10.0 to 3.0 ka BP, for which no written records exist. This Citation: Wu, L.; Lu, S.; Zhu, C.; review provides a comprehensive summary of materials that have been published over the past Ma, C.; Sun, X.; Li, X.; Li, C.; Guo, Q.
    [Show full text]
  • The Effect of Different Confluence Confirmation Strategies on the Obturation of Vertucci Type II Canal: Micro-CT Analysis
    Restor Dent Endod. 2021 Feb;46(1):e12 https://doi.org/10.5395/rde.2021.46.e12 pISSN 2234-7658·eISSN 2234-7666 Research Article The effect of different confluence confirmation strategies on the obturation of Vertucci type II canal: micro-CT analysis Seungjae Do , Min-Seock Seo * Department of Conservative Dentistry, Wonkwang University Daejeon Dental Hospital, Daejeon, Korea Received: Apr 8, 2020 Revised: Jun 7, 2020 ABSTRACT Accepted: Jun 17, 2020 Objectives: The present study aims to compare the obturation quality of 2 confluence Do S, Seo MS confirmation techniques in artificial maxillary first premolars showing Vertucci type II root canal configuration. *Correspondence to Min-Seock Seo, DDS, PhD Materials and Methods: Thirty artificial maxillary premolars having Vertucci type II root Associate Professor, Department of canal configuration were made. They were divided into 3 groups according to the confluence Conservative Dentistry, Wonkwang University confirmation technique as follows. Gutta-percha indentation (GPI) group (confluence Daejeon Dental Hospital, 77 Dunsan-ro, Seo- confirmation using a gutta-percha cone and a K file); electronic apex locator (EAL) group gu, Daejeon 35233, Korea. (confluence confirmation using K files and EAL); and no confluence detection (NCD) E-mail: [email protected] group. In the GPI group and the EAL group, shaping and obturation were performed with Copyright © 2021. The Korean Academy of the modified working length (WL). In the NCD group, shaping was performed without WL Conservative Dentistry adjustment and obturation was carried out with an adjusted master cone. Micro-computed This is an Open Access article distributed tomography was used before preparation and after obturation to calculate the percentage under the terms of the Creative Commons of gutta-percha occupied volume (%GPv) and the volume increase in the apical 4 mm.
    [Show full text]