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The degree of landscape connectivity has wide-ranging implications for sediment availability, frequency of transport, and the nature of sediment storage within a basin. Looking at the system as a whole, and identifying the connections that facilitate or impede sediment movement within a catchment is central to these applications. This thesis examines landscape connectivity within the highly diverse landscapes of the upper Yellow River (UYR) basin at a broad scale, with detailed focus on a smaller tributary that lies in the incised basin fill deposits of the Guide basin close to the margin of the Qinghai-Tibetan Plateau (QTP), the Garang subcatchment. Uplift of the QTP has resulted in a high-altitude landscape with a cold, semi-arid continental climate within the upper Yellow River. The region is characterized by several wide, low-relief basins separated by the two major mountain ranges (up to 2 km in relief) that run through the region, with tectonic deformation enduring within a series of strike-slip fault complexes. The thesis results are presented as a series of three papers. Findings are brought together in a discussion chapter. The first paper focuses on the pronounced variability in the landscapes of the upper Yellow River basin. The classification presented in this paper provides an effective organizational framework to describe the landscape diversity. Stark contrasts in landform assemblages and associated process relationships are evident across three very different terrains, reflecting the complex inter-relationships between tectonics, climate and surficial processes over time. A broad, low-relief, and highly disconnected upper plateau area at the headwaters of the UYR represents a relict peneplain that may have formed prior to regional uplift. The ranges of the Anyemaqen Shan in the central basin form a high-relief and highly connected landscape. Finally, the incisional story of the UYR dominates within the lower portion of the study area, where low-relief basin fills have been highly incised as a result of headward erosion of the Yellow River as drainage was established through the area. The second and third papers present a detailed examination of the landscape connectivity and sediment dynamics within the Garang study catchment. The second paper applies two methodological approaches for assessing landscape connectivity, a GIS-based geomorphometric index and a methodology linking interpretation of satellite imagery and field mapping of sediment storage to slope threshold analysis. Landscapes of the Garang catchment are differentiated into three geomorphic zones characterized by distinct landscape configuration and dominant geomorphic processes: i) a highly disconnected upper catchment of low-relief with large inactive sediment stores; ii) a transitional zone where present landscape dynamics are controlled in large part by past incisional processes in the form of large alluvial fan/terrace deposits; and iii) a highly connected and highly dissected landscape within the lower catchment that has little accommodation space for sediment storage. The findings from this paper emphasize the need for field-based observations that are capable of differentiating between landforms and activity levels of sediment stores, as well as providing inference on geomorphic process, that may not be evident with the use of cell-based morphometrics. The final paper expands upon these findings and presents an overview of sediment distribution and volume within the highly incised Garang catchment, combining field and GIS-based analyses. The magnitude and pattern of sediment storage is shown to be highly disparate between three distinct geomorphic zones of the Garang catchment. Findings of the study also reveal a somewhat unconventional pattern of sediment storage, whereby sediment storage is greater within the headwaters and decreases with distance downstream, adding to the range of landscape settings in which catchment-scale patterns of sediment storage have been assessed. The study also provides insight into the influence of long-term landscape evolution within the area, and how the response to lowering of the base level through Yellow River incision has impacted landscape connectivity and associated patterns of sediment storage and reworking within the catchment. Findings from both studies highlight the importance of field-informed appraisals of landscape dynamics, site-specific characteristics and the significance that basin-scale history can have on determining contemporary sediment dynamics. Issues associated with scales of analysis and the importance of localized influences are a key theme within the thesis. The final discussion chapter contextualizes findings of the thesis, focusing primarily on scale relations between landforms, geomorphic compartments (zones) and the subcatchment-scale analysis, and prospects to meaningfully up-scale these understandings to the UYR as a whole, linking analyses at the subcatchment scale to considerations of how we approach connectivity analyses across differing scales and contexts. Limitations and implications of the study are outlined.
This book offers a comprehensive review of the landscapes and ecosystems of the Upper Yellow River. It focuses on landscapes as a platform for considering environmental values and issues across the region. The book is based on extensive field-based analyses, applications, and photographs.
Rivers are the great shapers of terrestrial landscapes. Very few points on Earth above sea level do not lie within a drainage basin. Even points distant from the nearest channel are likely to be influenced by that channel. Tectonic uplift raises rock thousands of meters above sea level. Precipitation falling on the uplifted terrain concentrates into channels that carry sediment downward to the oceans and influence the steepness of adjacent hill slopes by governing the rate at which the landscape incises. Rivers migrate laterally across lowlands, creating a complex topography of terraces, floodplain wetlands and channels. Subtle differences in elevation, grain size, and soil moisture across this topography control the movement of ground water and the distribution of plants and animals. Rivers in the Landscape, Second Edition, emphasizes general principles and conceptual models, as well as concrete examples of each topic drawn from the extensive literature on river process and form. The book is suitable for use as a course text or a general reference on rivers. Aimed at advanced undergraduate students, graduate students, and professionals looking for a concise summary of physical aspects of rivers, Rivers in the Landscape is designed to: emphasize the connectivity between rivers and the greater landscape by explicitly considering the interactions between rivers and tectonics, climate, biota, and human activities; provide a concise summary of the current state of knowledge for physical process and form in rivers; reflect the diversity of river environments, from mountainous, headwater channels to large, lowland, floodplain rivers and from the arctic to the tropics; reflect the diverse methods that scientists use to characterize and understand river process and form, including remote sensing, field measurements, physical experiments, and numerical simulations; reflect the increasing emphasis on quantification in fluvial geomorphology and the study of Earth surfaces in general; provide both an introduction to the classic, foundational papers on each topic, and a guide to the latest, particularly insightful and integrative references.
A comprehensive, state-of-the-art synthesis of biogeochemical dynamics and the impact of human alterations at major river-coastal interfaces for advanced students and researchers.
Rill and gully erosion, as conditioned by actively migrating headcuts, contributes greatly to overall sediment yield from landscapes in a range of environments worldwide. Accurate prediction of rill and gully development in space and time remains elusive because gaps remain in our understanding of morphodynamics of rill and gully formative processes and the associated sedimentology. This research tackles a number of fundamental questions in order to further understanding and provide the basis for improvement of prediction technologies. A number of experimental and analytical approaches are used to investigate rill and gully development through headcut erosion. Headcut morphodynamics in stratified soils are examined in detail and shown to exhibit steady-state behavior. An analytical model of headcut development and migration is shown to be capable of predicting headcuts in stratified soils.^A numerical model is used to simulate ephemeral gully erosion driven by headcut migration over long time periods, under different agricultural management practices, in a range of environments. It is shown that ephemeral gully erosion repair through tillage operations greatly increases sediment yield over the no-till condition. Rill networks driven by exogenic forcing (headcuts created by baselevel drop) are examined in an experimental landscape using data acquisition techniques with very high spatial and temporal resolution. Detailed information on sediment budgeting through time and space is developed, as are longitudinal profiles, cross sections, and hydraulic geometry relationships. Headcut erosion is shown to be genetically linked to virtually all sediment detachment within the landscape. Baselevel adjustments resulted in peaks in sediment discharge as headcut-driven waves of degradation propagated throughout the landscape.^These waves of degradation were quickly and effectively communicated through the drainage network. Rates of headcut migration were shown to be well correlated to discharge. Stream order indices and fractal dimensions indicate that the rill network pattern emerges relatively early and remains relatively unchanged, despite continued application of rainfall. Rill basins do not exhibit self-affinity observed for river basins - they are geometrically self-similar at a range of scales within the experimental geomorphic environment.
This book focuses on a significant branch of anthropogeomorphology, which is not adequately studied: the impact of transportation systems on altering earth surface processes and landforms. This book fills the gap with in-depth study on the interaction between individual modes of transport network (e.g., trail, roads, railways, waterways, airports, and tunnel) and surface hydro-geomorphology with intensive literature review, fieldwork, geo-environmental modelling, mapping, case studies, and examples from different parts of the world. On the one hand, this book also addresses the vulnerability of transport networks from climate change and critical geo-hazards like floods, landslides, etc. with case studies from the high-risk zones of India. Overall, this book promotes peaceful harmony between the transport network and its surrounding landscapes as an essential lesson for policymakers, planners, and stakeholders.
A study of the geomorphology of rivers draining Mount Rainier, Washington, was completed to identify sources of sediment to the river network; to identify important processes in the sediment delivery system; to assess current sediment loads in rivers draining Mount Rainier; to evaluate if there were trends in streamflow or sediment load since the early 20th century; and to assess how rates of sedimentation might continue into the future using published climate-change scenarios. Rivers draining Mount Rainier carry heavy sediment loads sourced primarily from the volcano that cause acute aggradation in deposition reaches as far away as the Puget Lowland. Calculated yields ranged from 2,000 tonnes per square kilometer per year [(tonnes/km2)/yr] on the upper Nisqually River to 350 (tonnes/km2)/yr on the lower Puyallup River, notably larger than sediment yields of 50–200 (tonnes/km2)/yr typical for other Cascade Range rivers. These rivers can be assumed to be in a general state of sediment surplus. As a result, future aggradation rates will be largely influenced by the underlying hydrology carrying sediment downstream. The active-channel width of rivers directly draining Mount Rainier in 2009, used as a proxy for sediment released from Mount Rainier, changed little between 1965 and 1994 reflecting a climatic period that was relatively quiet hydrogeomorphically. From 1994 to 2009, a marked increase in geomorphic disturbance caused the active channels in many river reaches to widen. Comparing active-channel widths of glacier-draining rivers in 2009 to the distance of glacier retreat between 1913 and 1994 showed no correlation, suggesting that geomorphic disturbance in river reaches directly downstream of glaciers is not strongly governed by the degree of glacial retreat. In contrast, there was a correlation between active-channel width and the percentage of superglacier debris mantling the glacier, as measured in 1971. A conceptual model of sediment delivery processes from the mountain indicates that rockfalls, glaciers, debris flows, and main-stem flooding act sequentially to deliver sediment from Mount Rainier to river reaches in the Puget Lowland over decadal time scales. Greater-than-normal runoff was associated with cool phases of the Pacific Decadal Oscillation. Streamflow-gaging station data from four unregulated rivers directly draining Mount Rainier indicated no statistically significant trends of increasing peak flows over the course of the 20th century. The total sediment load of the upper Nisqually River from 1945 to 2011 was determined to be 1,200,000±180,000 tonnes/yr. The suspended-sediment load in the lower Puyallup River at Puyallup, Washington, was 860,000±300,000 tonnes/yr between 1978 and 1994, but the long-term load for the Puyallup River likely is about 1,000,000±400,000 tonnes/yr. Using a coarse-resolution bedload transport relation, the long-term average bedload was estimated to be about 30,000 tonnes/yr in the lower White River near Auburn, Washington, which was four times greater than bedload in the Puyallup River and an order of magnitude greater than bedload in the Carbon River. Analyses indicate a general increase in the sediment loads in Mount Rainier rivers in the 1990s and 2000s relative to the time period from the 1960s to 1980s. Data are insufficient, however, to determine definitively if post-1990 increases in sediment production and transport from Mount Rainier represent a statistically significant increase relative to sediment-load values typical from Mount Rainier during the entire 20th century. One-dimensional river-hydraulic and sediment-transport models simulated the entrainment, transport, attrition, and deposition of bed material. Simulations showed that bed-material loads were largest for the Nisqually River and smallest for the Carbon River. The models were used to simulate how increases in sediment supply to rivers transport through the river systems and affect lowland reaches. For each simulation, the input sediment pulse evolved through a combination of translation, dispersion, and attrition as it moved downstream. The characteristic transport times for the median sediment-size pulse to arrive downstream for the Nisqually, Carbon, Puyallup, and White Rivers were approximately 70, 300, 80, and 60 years, respectively.