Property:Theory movie
From CSDMS
This is a property of type Text.
E
Effects of high horizontal displacement rates on landscape evolution & pull-apart basins formation +
Basin and Landscape Dynamics (Badlands) is a parallel TIN-based landscape evolution model, built to simulate topography development at various space and time scales. The model is presently capable of simulating hillslope processes (linear diffusion), fluvial incision ('modified' SPL: erosion/transport/deposition), spatially and temporally varying geodynamic (horizontal + vertical displacements) and climatic forces which can be used to simulate changes in base level, as well as effects of climate changes or sea-level fluctuations. +
B
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment. +
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment. +
S
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment. +
B
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment. +
Braided steams can occur in drainage basins that have high sediment content and/or in river environments that rapidly change channel depth and thus velocity such as alluvial fans, river deltas and peneplains. +
Braided steams can occur in drainage basins that have high sediment content and/or in river environments that rapidly change channel depth and thus velocity such as alluvial fans, river deltas and peneplains. +
S
Close to 0.5 billion people live on, or near, world deltas, inclusively in many mega-cities. Ten countries (China, India, Bangladesh, Vietnam, Indonesia, Japan, Egypt, USA, Thailand, and the Philippines) account for 73% of the people that live in the world’s coastal zone, defined as within 10 m of mean sea level. 20th-century catchment developments and population and economic growth within subsiding deltas have placed these environments and their populations under a growing risk of coastal flooding, wetland loss, shoreline retreat, and loss of infrastructure.
To assess vulnerability of deltaic lowlands one has to look at a delta as a balance. A delta’s surface elevation above mean sea level can experience a vertical change relative to local mean sea level, ΔRSL. It is controlled by a summation of 5 factors:
(1) ΔRSL = A - ΔE - Cn - CA ± M
A delta’s Aggradation Rate (A) is determined from the volume of sediment delivered to and retained on the subaerial delta surface as new sedimentary layers due to flooding. A typically varies from 1 to 50 mm/y in deltas worldwide (See Table 1 in Syvitski et al., 2009). Most river floods bring large amounts of sediment to a delta’s surface. Reducing the number of distributary channels along with artificial levees can prohibit river flooding onto the delta plain. Flooding from ocean surges may still contribute additional turbid water.
ΔE is the Eustatic Sea Level Rate determined from changes to the volume of the global ocean over time, as influenced by fluctuations in the storage of terrestrial water (e.g. glaciers, ice sheets, groundwater, lakes, and reservoirs), and fluctuations in ocean water expansion due to water temperature changes. Presently ΔE is positive and contributes ≈1.8 to 3 mm/y (IPCC, 2007) under the anthropogenic influence of global warming. The IPCC projects that sea level will rise another 21 to 71 cm by 2070, with a best estimate of 44 cm averaged globally; it is becoming increasingly clear that the major ice sheets might contribute even more water over this period.
Natural Compaction (Cn), or Accelerated Compaction (CA) reduce the volume of deltaic deposits. Cn involves natural changes in the void space within sedimentary layers (e.g. dewatering, grain-packing realignment, and organic matter oxidation), and is typically ≤3 mm/y. CA is the anthropogenic contribution to volume change as a consequence of subsurface mining (oil, gas or groundwater), human-influenced soil drainage and accelerated oxidation. CA can exceed Cn by an order of magnitude.
M is the typically downward vertical movement of the land surface as influenced by the redistribution of earth masses (e.g. sea level fluctuations, growth of delta deposits, growth or shrinkage of nearby ice masses, tectonics, and deep-seated thermal subsidence). M is highly variable spatially but rates are typically between 0 and -5 mm/y.
T
Confluences are a common element of river networks, especially in the lower reaches and the deltaic floodplain. They are characterized by large-scale turbulent motions. Confluences are even more common in braided river networks, and play an important role in reworking and transporting bedload material. +
C
Confluences are a common element of river networks, especially in the lower reaches and the deltaic floodplain. They are characterized by large-scale turbulent motions. Confluences are even more common in braided river networks, and play an important role in reworking and transporting bedload material. +
Duperret et al. (2002) recently discussed bluff failure at Puys, 75 km to the northeast of the site of the video, Saint-Jouin-Bruneval. In that case they concluded that increased groundwater flow after heavy rain facilitated the collapse.
Coastal Rock Cliff Erosion by Collapse at Puys, France: The Role of Impervious Marl Seams within Chalk of NW Europe
Anne Duperret, Albert Genter, Rory N. Mortimore, Baptiste Delacourt and Mick R. De Pomerai
Journal of Coastal Research , Vol. 18, No. 1 (Winter, 2002), pp. 52-61 +
A
Erosion rates along permafrost coastlines of Alaska’s North Slope have been increasing over the past few decades (from 1953 onwards). The coast around Drew Point, roughly between Point Barrow and Prudhoe Bay along the Beaufort Sea, consists of ice-rich bluffs of about 3-5m high.
Thermal energy accounts for most of the erosion potential along these ice-rich permafrost coastlines, so predictive models of coastal erosion require an understanding of how sea-ice and sea surface temperatures evolve, both through the summer ice-free season and interannually.
To describe patterns of nearshore SST in the Beaufort Sea a team of USGS, INSTAAR and the Naval Postgraduate School deployed wave and ocean temperature sensors offshore from the National Petroleum Reserve in Alaska (NPR-A) during the summer of 2009. These sensors were placed in a shore-normal array between 0.2 and 10 km offshore, in water depths ranging from ~1m to 7m. Second, data is available from meteorological stations on the Alaskan North Slope to summarize the regional weather patterns that drive observed changes in ocean waves and temperatures over this time period. And lastly, we use satellite data to summarize sea ice position and sea surface temperatures over the past decade.
As long as the sea ice is still hugging the coast, which can be upto Halfway July, erosion is very limited. Subsequently, early in the summer when sea ice remains near the coast, the nearshore open water area is sheltered from mixing and warms to its highest temperatures of the summer. Water nearshore can become very warm, up to 10 degrees C, and consequently high thermal erosion occurs along the coast. As the sea ice margin retreats in mid-summer, summertime storsm homogenizes the temperatures offshore, collapsing the offshore temperature gradient to less than 0.5 degrees C per km and dropping the nearshore temperatures by almost 5 degrees C. Thermal erosion potential is consequently reduced later in the summer.
In the Fall season the sea surface water temperature drops to about 2 to -1 degrees C and there may be less potential for erosion.
S
Fluvial coastal reworking as a result of sea level change in glacial-interglacial time periods. +
D
Fluvial system alternates between sediment storage and release due to autogenic slope fluctuations on the deltaic surface. Shoreline progradation rates increase during release events and slow during sediment storage. This process is entirely autogenic (internally generated, i.e., no external controls were changing to induce this process). +
P
GIPL was used to simulate the dynamics of the active layer thickness and mean annual ground temperature, both retrospectively and prognostically, using climate forcing from Global Climate Models. GIPL is a numerical model based on a finite difference method for the non-linear Heat Conduction Equation.
In this model the process of soil freezing/thawing is occurring in accordance with the unfrozen water content curve, which is specific for each soil layer and for each geographical location. For each grid point on the map we used a one-dimensional multi-layer model of soil down to the depth of a constant geothermal heat flux (typically 500 to 1000 m). At the upper boundary, there are insulating layers of snow and vegetation that can change their properties with time. Special Enthalpy formulation of the energy conservation law makes it possible to use a coarse vertical resolution without loss of latent heat effects in phase transition zone even in case of fast temporally and spatially varying temperature fields. The new version of GIPL (GIPL 2.0) calculates soil temperature and liquid water content fields for the entire spatial domain with daily, monthly and yearly resolutions. The merge of the new GIPL and the GIS technique provides a unique opportunity to analyze spatial features of permafrost dynamics into the future. +
G
Glacial surges are short-lived events where a glacier can move up to velocities 100 times faster than normal, and advance substantially. Surging glaciers are found in only a few areas: Svalbard, Canadian Arctic islands, and Alaska.
Glacial surges can take place at regular, periodic intervals. In some glaciers, surges can occur in fairly regular cycles with 15 to 100 or more surge events per year. In other glaciers, surging is unpredictable. In some glaciers, the period of stagnation and build-up between two surges typically lasts 10-200 years and is called the quiescent phase. During this period the velocities of the glacier are significantly lower, and during those periods the glaciers can retreat substantially.
Glaciers in Alaska exhibit surges with a sudden onset, extremely high (tens of meters/day) maximum flow rate and a sudden termination, often with a discharge of stored water. These are called Alaskan-type surges and it is suspected that these surges are hydrologically controlled. Outburst flows are often associated with these events.
Surges may also be caused by the supply of meltwater to the base of a glacier. Meltwater is important in reducing frictional restrictions to glacial ice flow. The distribution and pressure of water at the bed modulates the glaciers velocity and therefore mass balance. Meltwater may come from a number of sources, including supraglacial lakes, geothermal heating of the bed, conduction of heat into the glacier and latent heat transfers. There is a positive feedback between velocity and friction at the bed, high velocities will generate more frictional heat and create more meltwater. Crevassing is also enhanced by greater velocity flow which will provide further rapid transmission paths for meltwater flowing towards the bed. The evolution of the drainage system under the glacier may play a key role in surge cycles.
In contrast, surging glaciers in Svalbard appear to have a much slower surging cycle. Monaconbreen in Svalbard surged over several years, and maximum speeds were much less high than measured in Alaska.
M
Global temperature distribution is derived from remote sensing data gathered from satellites. One of the instruments used in measuring land surface temperatures is ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) which is aboard the TERRA satellite. The orbiting satellites gather data regarding the reflection of various wavelength bands from earth’s surface which can then be used to create temperature profiles for a given region. These temperatures are then compared with local observing stations to validate and help calibrate the computed data. With global temperature data distributed over a large enough time scale, representative means can be created these means are then compiled to create global temperature profiles. +
G
Gravity driven waves (swell) conserve energy as they move through the worlds oceans. Thus it is possible to track ocean energy as it moves through the worlds oceans and interacts with land forms.
Wave power is approximately calculated as
E=.125(pgH^2). Where E is energy, p is the density of water, g is acceleration due to gravity and H is wave height. +
P
Heavier sediment settles first resulting in highly stratified delta formation. +
S
High river water that does not overtop a levee yet, can still create a tremendous water pressure. This pressure creates a potential for groundwater seepage of the water, through the underlying, permeable aquifer into the lowlands that are protected from direct flooding by an largely impermeable levee.
Sand and water start bubbling up on the floodplain; usually indicating that undermining of the levee is going on. +
