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Chris Paola - One of the best experts on this subject based on the ideXlab platform.
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on the connections between surficial processes and stratigraphy in River Deltas
arXiv: Geophysics, 2016Co-Authors: Michael J Puma, Chris Paola, Andrea Rinaldo, Rachata Muneepeerakul, Ignacio RodrigueziturbeAbstract:We explore connections between surficial deltaic processes (e.g. avulsion, deposition) and the stratigraphic record using a simple numerical model of delta-plain evolution, with the aim of constraining these connections and thus improving prediction of subsurface features. The model represents channel dynamics using a simple but flexible cellular approach, and is unique in that it explicitly includes backwater effects that are known to be important in low-gradient channel networks. The patterns of channel deposits in the stratigraphic record vary spatially due to variation in avulsion statistics with radial distance from the delta's source of water and sediment. We introduce channel residence time as an important statistical measure of the surface channel kinematics. The model suggests that the mean channel residence time anywhere within the delta is nicely described by a power law distribution showing a cutoff that depends on radial distance. Thicknesses of channel deposits are not uniquely determined by the residence time of channelization. The channel residence time distributions at given radial distances from the source are found to be approximately lognormally distributed, a finding consistent with the scale-dependent radial structure of channel deposits in the stratigraphic record.
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characterization of River delta shorelines
Geophysical Research Letters, 2012Co-Authors: N Geleynse, Vamsi Ganti, Chris Paola, Vaughan R VollerAbstract:[1] Coastline shape is among the basic geometric properties of the Earth's surface, yet defining and quantifying coastline shape precisely remains challenging. Here we propose new methods, based on the dilation and erosion operators of mathematical morphology (MM), for the characterization of delta shorelines, a class of open coasts. We demonstrate the suitability of MM-based methods for noise removal and shoreline identification from digital images of River Deltas of varying geometric complexity. We also show that a global, a regional and a local shoreline parameter provide a first step in distinguishing among River, wave, and tidal dominated delta shapes.
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quantitative metrics that describe River Deltas and their channel networks
Journal of Geophysical Research, 2011Co-Authors: Douglas A Edmonds, Chris Paola, David C Hoyal, Ben SheetsAbstract:[1] Densely populated River Deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology. Toward this end we present a set of five metrics that describe delta morphology: (1) the fractal dimension, (2) the distribution of island sizes, (3) the nearest-edge distance, (4) a synthetic distribution of sediment fluxes at the shoreline, and (5) the nourishment area. The nearest-edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks. The nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks. As a first step, we apply these metrics to four relatively simple, fluvially dominated delta networks. For all these Deltas, the average nearest-edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel. Nourishment area distributions can be predicted from a River mouth bar model of delta growth, and also scale with the width of the channel and with the length of the longest channel, analogous to Hack's law for drainage basins. The four delta channel networks are fractal, but power laws and scale invariance appear to be less pervasive than in tributary networks. Thus, Deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity, where morphologic differences indicate different behavior.
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delta allometry growth laws for River Deltas
Geophysical Research Letters, 2010Co-Authors: Matthew A Wolinsky, Douglas A Edmonds, John Martin, Chris PaolaAbstract:[1] Under projected scenarios of sea-level rise, subsidence, and sediment starvation many Deltas around the world are expected to drown. Delta growth dynamics, which determine the ability of a delta to adapt to these changes, are poorly understood due to the difficulty of measuring change in slowly evolving landscapes. We use time-series imagery of experimental, numerical, and field-scale Deltas to derive four laws that govern the growth of River-dominated Deltas. Land area grows at a constant rate in the absence of relative sea level change, while wetted area keeps pace, maintaining a constant wetted fraction over the delta surface. Scaling of edge-lengths versus areas suggests delta shorelines are nonfractal, even though the channel network is fractal. Consequently channel-edge length, which provides critical habitat, grows more rapidly than delta area. These laws provide a blueprint for delta growth that will aid in delta restoration and help predict how existing Deltas will evolve.
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battling to save the world s River Deltas
Bulletin of The Atomic Scientists, 2009Co-Authors: Charles J Vorosmarty, Liviu Giosan, James P M Syvitski, John W Day, Alex De Sherbinin, Chris PaolaAbstract:The fragility of the world’s Deltas is not solely a consequence of rising ocean waters. Human fresh water use is a predominant force behind receding coastlines.
Matthew A Wolinsky - One of the best experts on this subject based on the ideXlab platform.
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delta allometry growth laws for River Deltas
Geophysical Research Letters, 2010Co-Authors: Matthew A Wolinsky, Douglas A Edmonds, John Martin, Chris PaolaAbstract:[1] Under projected scenarios of sea-level rise, subsidence, and sediment starvation many Deltas around the world are expected to drown. Delta growth dynamics, which determine the ability of a delta to adapt to these changes, are poorly understood due to the difficulty of measuring change in slowly evolving landscapes. We use time-series imagery of experimental, numerical, and field-scale Deltas to derive four laws that govern the growth of River-dominated Deltas. Land area grows at a constant rate in the absence of relative sea level change, while wetted area keeps pace, maintaining a constant wetted fraction over the delta surface. Scaling of edge-lengths versus areas suggests delta shorelines are nonfractal, even though the channel network is fractal. Consequently channel-edge length, which provides critical habitat, grows more rapidly than delta area. These laws provide a blueprint for delta growth that will aid in delta restoration and help predict how existing Deltas will evolve.
Paola Passalacqua - One of the best experts on this subject based on the ideXlab platform.
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the delta connectome a network based framework for studying connectivity in River Deltas
Geomorphology, 2017Co-Authors: Paola PassalacquaAbstract:Abstract Many Deltas, including the Mississippi River Delta, have been losing land at fast rates compromising the safety and sustainability of their ecosystems. Knowledge of delta vulnerability has raised global concern and stimulated active interdisciplinary research as Deltas are densely populated landscapes, rich in agriculture, fisheries, oil and gas, and important means for navigation. There are many ways of looking at this problem which all contribute to a deeper understanding of the functioning of coastal systems. One aspect that has been overlooked thus far, yet fundamental for advancing delta science is connectivity , both physical (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). In this paper, I propose a framework called Delta Connectome for studying connectivity in River Deltas based on different representations of a delta as a network. After analyzing the classic network representation as a set of nodes (e.g., bifurcations and junctions or regions with distinct physical or statistical behavior) and links (e.g., channels), I show that from connectivity considerations the delta emerges as a leaky network that continuously exchanges fluxes of matter, energy, and information with its surroundings and evolves over time. I explore each network representation and show through several examples how quantifying connectivity can bring to light aspects of deltaic systems so far unexplored and yet fundamental to understanding system functioning and informing coastal management and restoration. This paper serves both as an introduction to the Delta Connectome framework as well as a review of recent applications of the concepts of network and connectivity to deltaic systems within the Connectome framework.
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how much subsidence is enough to change the morphology of River Deltas
Geophysical Research Letters, 2016Co-Authors: M Liang, Wonsuck Kim, Paola PassalacquaAbstract:Understanding the effect of subsidence on fluviodeltaic morphology is important not only to maintain sustainable coastal cities and habitats but also to interpret the information contained in the stratigraphic record. While tectonic steering in alluvial environments has been investigated, similar studies in fluviodeltaic environments are limited to physical experiments and field observations. We perform numerical experiments with a parcel-based cellular model to analyze the deltaic surface and subsurface responses to regional subsidence. We quantify model results using robust metrics and show that while sediment partitioning and shoreline pattern vary gradually with increasing subsidence rate, channel mobility and stratigraphic connectivity of channel deposits show a threshold transition. Conditions for this transition are captured with a dimensionless filling index β, defined as the ratio between the rates of accommodation creation and sediment supply. A channel-locking mechanism activates when β exceeds 0.6 and is responsible for the threshold transition.
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quantifying the patterns and dynamics of River Deltas under conditions of steady forcing and relative sea level rise
Journal of Geophysical Research, 2016Co-Authors: M Liang, Corey Van Dyk, Paola PassalacquaAbstract:Understanding deltaic channel dynamics is essential to acquiring knowledge on how Deltas respond to environmental changes, as channels control the distribution of water, sediment, and nutrients. Channel-resolving morphodynamic models provide the basis for quantitative study of channel-scale dynamics, but they need to be properly assessed with a set of robust metrics able to quantitatively characterize delta patterns and dynamics before being used as predictive tools. In this work we use metrics developed in the context of delta formation, to assess the morphodynamic results of DeltaRCM, a parcel-based cellular model for delta formation and evolution. By comparing model results to theoretical predictions and field and experimental observations, we show that DeltaRCM captures the geometric growth characteristics of Deltas such as fractality of channel network, spatial distribution of wet and dry surfaces, and temporal dynamics of channel-scale processes such as the decay of channel planform correlation. After evaluating the ability of DeltaRCM to produce delta patterns and dynamics at the scale of channel processes, we use the model to predict the deltaic response to relative sea level rise (RSLR). We show that uniform subsidence and absolute sea level rise have similar effects on delta evolution and cause intensified channel branching. Channel network fractality and channel mobility increase with higher-RSLR rates, while the spatial and temporal scales of avulsion events decrease, resulting in smaller sand bodies in the stratigraphy. Our modeling results provide the first set of quantitative predictions of the effects of RSLR on River Deltas with a specific focus on the distributary channel network.
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hydrological connectivity in River Deltas the first order importance of channel island exchange
Water Resources Research, 2015Co-Authors: Matthew Hiatt, Paola PassalacquaAbstract:Deltaic systems are composed of distributary channels and interdistributary islands. While previous work has focused either on the channels or on the islands, here we study the hydrological exchange between channels and islands and point at its important role in delta morphology and ecology. We focus our analysis on Wax Lake Delta in coastal Louisiana (USA) and characterize the surface water component of hydrological connectivity through measurements of water discharge and hydraulic tracer propagation. We find that deltaic islands are zones of significant water flux as 23–54% of the incoming distributary channel flux enters the islands. A calculation of the travel times through a channel-island complex shows travel times through the islands to be at least 3 times their channel counterparts. A dye release experiment also indicates that travel times in islands are much longer that those within channels as dye remained in the island for the 3.8 day duration of the experiment. Additionally, islands are more sensitive than channels to environmental forces such as tides, which cause flow reversal and thus can increase travel times through the islands. Our work defines the “hydrological network” of a River delta to include not only the distributary channel network but also the interdistributary islands, quantifies the implications of channel-island hydrological connectivity to travel times through the system, and discusses the relevance of our findings to channel mouth dynamics at the delta front and the potential for denitrification in coastal systems.
M. V. Mikhailova - One of the best experts on this subject based on the ideXlab platform.
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internal and external water exchange in nontidal River Deltas
Water Resources, 2019Co-Authors: M. V. Mikhailova, M V IsupovaAbstract:The types and specific features of the internal and external water exchange in nontidal Deltas are discussed. The results of hydraulic calculation of water exchange in the branch–bypass–delta lake are given. The conclusions are confirmed by data of observations in several large nontidal and microtidal Deltas.
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Many-year variations in River delta structures
Water Resources, 2016Co-Authors: M. V. MikhailovaAbstract:Data on several River Deltas are used to analyze the regularities in their dynamics in the context of variations of water and sediment runoff, sea level, and hydroengineering activities in delta areas. The basis for this analysis includes the results of many-year studies of River Deltas in Russia and the world. The specific features of the evolution of the structure and morphometry of bayhead Deltas, forming in bays, lagoons, and estuaries are shown in the case of the Alikazgan delta in the Terek mouth area and the Deltas of two watercourses in the Mississippi mouth area. Data on many-year variations of the morphometric characteristics of modern protruding Deltas in open coastal zones are systematized, and the factors that have an effect on these changes are analyzed. The types of delta formation processes and the types of Deltas are considered with regard to the factors involved. The majority of modern River Deltas are found to slow down their progradation into seas under the effect of anthropogenic runoff decline; moreover, some Deltas have started retreating and degrading.
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impact of local water management and hydraulic engineering projects on River Deltas
Water Resources, 2015Co-Authors: V. N. Mikhailov, M. V. MikhailovaAbstract:The history of economic development of River Deltas and the main types of local water management and hydraulic-engineering projects aimed at using and protecting the natural resources are discussed. The specific features of such projects include diking of branches and deltaic islands, artificial flow redistribution in Deltas, engineering work on improvement of navigation conditions, and anthropogenic transformation of the surface of Deltas. The hydrological, morphological, and environmental consequences of these projects are analyzed. Close attention is given to the maim methods of analysis, calculation, and prediction of the impact of local water management activities on the regime, structure, and ecosystems of Deltas. Mention is made of adverse effects of some projects in particular Deltas, designed and accomplished without considering specific features of Deltas as unified hydraulic-morphological systems, and possible consequences of these projects.
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morphometry of River Deltas
Water Resources, 2015Co-Authors: M. V. MikhailovaAbstract:The modern morphometry of Deltas of numerous Rivers of the world was studied using cartographic and satellite data. The Deltas were subdivided into two groups: bayhead Deltas of sea bays, limans, lagoons, and estuaries and protruding Deltas on open coasts of seas and lakes. The morphometric parameters measured for both delta types include delta length along its main branch, the length of its marginal coastline (sea, lake, liman, and lagoon), delta area, and the number of mouths of main branches; some morphometric parameters were calculated. Regression analysis was used to study the relationships between the morphometric delta parameters taken in pairs as well as between these parameters and the values of external factors responsible for delta formation (first of all, water and sediment River runoff). The closeness of the calculated empirical relationships was assessed. Considerable differences were revealed in the obtained relationships for the two types of Deltas. Based on the calculations, two geometric models of typical Deltas were proposed: bayhead delta and protruding delta. The obtained results can be used for approximate assessment of possible changes in River Deltas under the condition of variations in River water and sediment runoff and in the sea level.
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Regularities in sea level rise impact on the hydrological regime and morphological structure of River Deltas
Water Resources, 2010Co-Authors: V. N. Mikhailov, M. V. MikhailovaAbstract:The problem of assessment of sea level rise impact on the hydrological regime and morphological structure of River Deltas is discussed. Studies of the response of River Deltas, which are among the most vulnerable natural objects, to the sea level rise has become urgent because of the global climate warming and the associated acceleration of the World Ocean level rise. Methods are described that can be used for the analysis, calculation, and prediction of sea level rise impact on submergence of Deltas, propagation of backwater from the sea tides, surges, and salt seawater intrusion. Special emphasis is given to channel processes in delta branches, which accompany sea level rise, as well as to delta coastline erosion and flow redistribution among branches. In the course of research, due consideration was taken of the experience gained in studying the response of River Deltas on the Caspian Sea coasts to the recent considerable level rise in this water body.
Douglas A Edmonds - One of the best experts on this subject based on the ideXlab platform.
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coastal flooding will disproportionately impact people on River Deltas
Nature Communications, 2020Co-Authors: Douglas A Edmonds, Rebecca L Caldwell, Eduardo S Brondizio, Sacha M O SianiAbstract:Climate change is intensifying tropical cyclones, accelerating sea-level rise, and increasing coastal flooding. River Deltas are especially vulnerable to flooding because of their low elevations and densely populated cities. Yet, we do not know how many people live on Deltas and their exposure to flooding. Using a new global dataset, we show that 339 million people lived on River Deltas in 2017 and 89% of those people live in the same latitudinal zone as most tropical cyclone activity. We calculate that 41% (31 million) of the global population exposed to tropical cyclone flooding live on Deltas, with 92% (28 million) in developing or least developed economies. Furthermore, 80% (25 million) live on sediment-starved Deltas, which cannot naturally mitigate flooding through sediment deposition. Given that coastal flooding will only worsen, we must reframe this problem as one that will disproportionately impact people on River Deltas, particularly in developing and least-developed economies.
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entropy and optimality in River Deltas
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Alejandro Tejedor, Douglas A Edmonds, Anthony Longjas, Ilya Zaliapin, Tryphon T Georgiou, Andrea Rinaldo, Efi FoufoulageorgiouAbstract:The form and function of River Deltas is intricately linked to the evolving structure of their channel networks, which controls how effectively Deltas are nourished with sediments and nutrients. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. To date, however, a unified theory explaining how Deltas self-organize to distribute water and sediment up to the shoreline remains elusive. Here, we provide evidence for an optimality principle underlying the self-organized partition of fluxes in delta channel networks. By introducing a suitable nonlocal entropy rate ([Formula: see text]) and by analyzing field and simulated Deltas, we suggest that delta networks achieve configurations that maximize the diversity of water and sediment flux delivery to the shoreline. We thus suggest that prograding Deltas attain dynamically accessible optima of flux distributions on their channel network topologies, thus effectively decoupling evolutionary time scales of geomorphology and hydrology. When interpreted in terms of delta resilience, high nER configurations reflect an increased ability to withstand perturbations. However, the distributive mechanism responsible for both diversifying flux delivery to the shoreline and dampening possible perturbations might lead to catastrophic events when those perturbations exceed certain intensity thresholds.
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quantitative metrics that describe River Deltas and their channel networks
Journal of Geophysical Research, 2011Co-Authors: Douglas A Edmonds, Chris Paola, David C Hoyal, Ben SheetsAbstract:[1] Densely populated River Deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology. Toward this end we present a set of five metrics that describe delta morphology: (1) the fractal dimension, (2) the distribution of island sizes, (3) the nearest-edge distance, (4) a synthetic distribution of sediment fluxes at the shoreline, and (5) the nourishment area. The nearest-edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks. The nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks. As a first step, we apply these metrics to four relatively simple, fluvially dominated delta networks. For all these Deltas, the average nearest-edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel. Nourishment area distributions can be predicted from a River mouth bar model of delta growth, and also scale with the width of the channel and with the length of the longest channel, analogous to Hack's law for drainage basins. The four delta channel networks are fractal, but power laws and scale invariance appear to be less pervasive than in tributary networks. Thus, Deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity, where morphologic differences indicate different behavior.
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delta allometry growth laws for River Deltas
Geophysical Research Letters, 2010Co-Authors: Matthew A Wolinsky, Douglas A Edmonds, John Martin, Chris PaolaAbstract:[1] Under projected scenarios of sea-level rise, subsidence, and sediment starvation many Deltas around the world are expected to drown. Delta growth dynamics, which determine the ability of a delta to adapt to these changes, are poorly understood due to the difficulty of measuring change in slowly evolving landscapes. We use time-series imagery of experimental, numerical, and field-scale Deltas to derive four laws that govern the growth of River-dominated Deltas. Land area grows at a constant rate in the absence of relative sea level change, while wetted area keeps pace, maintaining a constant wetted fraction over the delta surface. Scaling of edge-lengths versus areas suggests delta shorelines are nonfractal, even though the channel network is fractal. Consequently channel-edge length, which provides critical habitat, grows more rapidly than delta area. These laws provide a blueprint for delta growth that will aid in delta restoration and help predict how existing Deltas will evolve.
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predicting delta avulsions implications for coastal wetland restoration
Geology, 2009Co-Authors: Douglas A Edmonds, David C Hoyal, Ben Sheets, Rudy SlingerlandAbstract:River Deltas create new wetlands through a continuous cycle of delta lobe extension, avulsion, and abandonment, but the mechanics and timing of this cycle are poorly understood. Here we use physical experiments to quantitatively define one type of cycle for River-dominated Deltas. The cycle begins as a distributary channel and its River mouth bar prograde basinward. Eventually the mouth bar reaches a critical size and stops prograding. The stagnated mouth bar triggers a wave of bed aggradation that moves upstream and increases overbank flows and bed shear stresses on the levees. An avulsion occurs as a time-dependent failure of the levee, where the largest average bed shear stress has been applied for the longest time (R 2 = 0.93). These results provide a guide for predicting the growth of intradelta lobes, which can be used to engineer the creation of new wetlands within the delta channel network and improve stratigraphic models of Deltas.
