Property:Theory movie
From CSDMS
This is a property of type Text.
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A calving glacier (also called tidewater glacier) is a glacier that ends in a body of water. Calving glaciers occur in Alaska, Arctic Canada, Patagonia, as well as along the Greenlandic Ice Sheet and Antarctica.
It is these systems that produce icebergs floating in the world oceans.
Calving glaciers behave very differently than land-based glaciers. Their velocity accelerates at the terminus, and they are much more dynamic than land-based glaciers. Calving glaciers need a large accumulation area to compensate for the ice mass lost by calving.
Calving rates of tidewater glaciers in Alaska were found to be controlled by the depth of the water at the glacier front (Brown et al., 1982).
Vc=CHw+D
Vc = calving speed (m/yr)
C = calving coefficient (27.1 +/- 2 per yr for a study of 13 Alaskan glaciers)
Hw = water depth at the glacier front (m)
D = constant (0 m/yr for a study of 13 Alaskan glaciers)
Calving glaciers can advance and retreat at great rates. Some of the Alaskan calving glaciers retreated over > 100 km in the last two centuries. +
D
A debris flow is a fast moving mass of unconsolidated, saturated debris that looks like flowing concrete. They differentiate from a mudflow by terms of the viscosity of the flow. Flows follow a steepest descent generally, although they are known the “climb” opposite valley walls in extreme cases. The front of the debris flow, or the toe, forms a lobe, marking flow front. This lobe often contains a great deal of the larger sediments including cobbles and boulders. Early pulses or previous debris flows form levees that channel the flow until they are breached. The presence of older levees indicates the recurrence and characteristics of debris flows in a particular area. This can be an important indicator of past debris flow activity for developing land on alluvial fan terrace surfaces.
But, flows can carry clasts ranging in size from clay particles to boulders, and may contain woody debris. During later phases of the event, more viscous mud that contains sands, silts, and fines runs through the flowpath.
Debris flows can be triggered by large amounts of rainfall, snow melt, or glacial/permafrost melt, or a combination of all. Speed of debris flows can vary from 0.5 m/s to 16 m/s in extreme conditions.
Variables in the conditions that affect debris flow characteristics are slope, available sediment and vegetation in the flowpath.
Debris flow are extremely destructive to life and property.
This particular event happened on July 2nd, 2006. This is during the middle of the Southern Hemisphere's Austral Winter, but the temperature was unseasonally high at 32º C! It was the warmest July day ever recorded (pers. comm. W. Keller). This debris flow event is attributed to hydrothermal alteration of the local mountain flank and the melting of permafrost. +
U
A debris flow is characterized as a liquefied mixture of sediment and water flowing down a slope. It is driven by the gravity acting on the sediment. +
N
A delta is formed by the interaction of three main controls: river energy, wave energy or tidal energy. Deltas are often classified by their morphological characteristics and the dominant controlling factor cinfluencing its morphology. An open ocean basin has a potential for high wave energy. High wave interference causes conflicted or deflected river mouths. There is less influence from fluvial sources. In wave-dominated delta regions, breaking waves cause immediate mixing of fresh and salt water. Typically, the fresh water flow velocity decelerates rapidly. A bar may form in the immediate vicinity of the distributary mouth, often supplemented by landward migrating swash bars. The wave action reworks the sediment, making it much sandier than other types of deltas. Alternatively, sediment is delivered by the river and but it is immediately transported along the coast. The sediment is then deposited as beaches and bars and the development of distributaries is limited. Dominant directions of wave approach can result in asymmetric beach ridges, and may cause the progradation of a spit across the river mouth. This results in channel flow oblique or parallel to the shore.
For the theory behind the models of this coupled river and wave-dominated coast simulations see the Model Help of the Coastline Evolution Model: https://csdms.colorado.edu/wiki/Model_help:CEM and the Model help of HydroTrend: https://csdms.colorado.edu/wiki/Model_help:HydroTrend
This movie can be linked to the lab and lecture on coupled delta modeling:
https://csdms.colorado.edu/wiki/SurfaceDynamics_Modeling_CMT
https://csdms.colorado.edu/wiki/Labs_portal +
W
A delta is formed by the interaction of three main controls: river energy, wave energy or tidal energy. Deltas are often classified by their morphological characteristics and the dominant controlling factor cinfluencing its morphology. An open ocean basin has a potential for high wave energy. High wave interference causes conflicted or deflected river mouths. There is less influence from fluvial sources. In wave-dominated delta regions, breaking waves cause immediate mixing of fresh and salt water. Typically, the fresh water flow velocity decelerates rapidly. A bar may form in the immediate vicinity of the distributary mouth, often supplemented by landward migrating swash bars. The wave action reworks the sediment, making it much sandier than other types of deltas. Alternatively, sediment is delivered by the river and but it is immediately transported along the coast. The sediment is then deposited as beaches and bars and the development of distributaries is limited. Dominant directions of wave approach can result in asymmetric beach ridges, and may cause the progradation of a spit across the river mouth. This results in channel flow oblique or parallel to the shore.
For the theory behind the models of this coupled river and wave-dominated coast simulations see the Model Help of the Coastline Evolution Model: https://csdms.colorado.edu/wiki/Model_help:CEM and the Model help of HydroTrend: https://csdms.colorado.edu/wiki/Model_help:HydroTrend +
J
A glacial lake outburst flood occurs when massive amounts of meltwater are dramatically released. This can be for several reasons: when a lake contained by a glacier or a moraine dam drains. One distinguishes between a ‘Jökulhlaup’, if the lake formed subglacially, or a ‘marginal lake drainage’ if it was dammed between ice and the ground.
Glacial outburst flows can happen due to erosion, a buildup of water pressure, an avalanche of rock or heavy snow, an earthquake or cryoseism, volcanic eruptions under the ice, or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base.
A jökulhlaup is thus a sub-glacial outburst flood. Jökulhlaup is an Icelandic term that has been adapted into the English language, and originally only referred to glacial outburst floods, which are triggered by volcanic eruptions, but now is accepted to describe any abrupt and large release of sub-glacial water.
Glacial lakes come in various sizes, but may hold millions to hundreds of millions of cubic meters of water. Catastrophic failure of the containing ice or glacial sediment can release this water over a timespan of minutes to days. Peak flows as high as 15,000 cubic meters per second have been recorded in these events. On a downstream floodplain, inundation can spread as much as 10 kilometers wide. Both scenarios are horrific threats to lives, property and infrastructure. +
A glacial lake outburst flood occurs when massive amounts of meltwater are dramatically released. This can be for several reasons: when a lake contained by a glacier or a moraine dam drains. One distinguishes between a ‘Jökulhlaup’, if the lake formed subglacially, or a ‘marginal lake drainage’ if it was dammed between ice and the ground.
Glacial outburst flows can happen due to erosion, a buildup of water pressure, an avalanche of rock or heavy snow, an earthquake or cryoseism, volcanic eruptions under the ice, or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base.
A jökulhlaup is thus a sub-glacial outburst flood. Jökulhlaup is an Icelandic term that has been adapted into the English language, and originally only referred to glacial outburst floods, which are triggered by volcanic eruptions, but now is accepted to describe any abrupt and large release of sub-glacial water.
Glacial lakes come in various sizes, but may hold millions to hundreds of millions of cubic meters of water. Catastrophic failure of the containing ice or glacial sediment can release this water over a timespan of minutes to days. Peak flows as high as 15,000 cubic meters per second have been recorded in these events. On a downstream floodplain, inundation can spread as much as 10 kilometers wide. Both scenarios are horrific threats to lives, property and infrastructure. +
R
A groyn is a rigid hydraulic structure built from an ocean shore (in coastal engineering) or from a bank (in rivers) that interrupts water flow and limits the movement of sediment. In some cases it keeps velocity in the main channel such that it is suitable for shipping.
In a river, groynes prevent bank erosion and ice-jamming, which in turn aids navigation. The areas between groups of groynes are groyne fields. Groynes can be made of wood, concrete, or rock piles. Their use goes back many centuries. +
A groyn is a rigid hydraulic structure built from an ocean shore (in coastal engineering) or from a bank (in rivers) that interrupts water flow and limits the movement of sediment. In some cases it keeps velocity in the main channel such that it is suitable for shipping.
In a river, groynes prevent bank erosion and ice-jamming, which in turn aids navigation. The areas between groups of groynes are groyne fields. Groynes can be made of wood, concrete, or rock piles. Their use goes back many centuries. +
L
A landslide is a mass movement along a failure plane on a slope. Landslides occur when the stability threshold of a slope is overcome. The trigger can be abrupt, like an earthquake or more gradual due to a number of factors including:
# porewater pressure built up due to extensive rainfall, snow of glacier melt.
# undercutting of a slope by a river or wave erosion.
Fires and deforestation that change the water infiltration capacity of a slope do influence the probability of a landslide event happening.
A elaborate discussion on classification can be found here: http://en.wikipedia.org/wiki/Landslide_classification +
V
A lot of background information on this eruption can be found on:
http://en.wikipedia.org/wiki/2010_eruptions_of_Eyjafjallajökull +
T
A tidal bore, also called aegir, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave of water that travel up a river or narrow bay against the river current. As such, it is a true tidal wave.
Bores occur in relatively few locations, but they do occur worldwide, usually in areas with a large tidal range (typically more than 6 m between high and low water).
All these locations are shallow, narrowing rivers or fjords in which water is funneled via a broad bay. The funnel-like shape not only increases the height of the tide, but it can also decrease the duration of the flood tide down to a point where the flood appears as a sudden increase in the water level. The rising tide may force the tidal wave-front to move faster that a shallow water wave can propagate into water of that depth:<br>
T=L/(c+u)<br>
T = wave period<br>
L = wave length<br>
c = wave speed<br>
u = speed of current<br>
If the current flows counter the direction of wave propagation, then L will increase and the wave will get shorter and higher (upto the point of breaking).
Bore tides come in after extreme minus low tides created by the full or new moon (Chanson, 2004).
Bores take on various forms, ranging from a single breaking wavefront —like a shock wave — to ‘undular bores’ comprising a smooth wavefront followed by a train of secondary waves (whelps). Large bores can be dangerous for shipping.
Rivers that do have a tidal bore include the Amazon and Orinoco Rivers, in South America, the Hoogly River in the Ganges-Brahmaputra delta, several rivers in the UK, and rivers draining into the Bay of Fundy. The largest tidal bore occurs in the Qiantang River in China, it is 9m high and travels at 40 km/hr.
Tidal bores have distinct influence on sediment transport. The arrival of the borefront is associated with intense bed shear stress and bed scour. Suspended sediment is advected upwards in the wake of the tidal bore. This phase is associated with turbulent structure. The suspension of sediment is sustained by wave motion for several minutes to half an hour after the bore has passed (Chanson, 2004).
A tidal bore, also called aegir, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave of water that travel up a river or narrow bay against the river current. As such, it is a true tidal wave.
Bores occur in relatively few locations, but they do occur worldwide, usually in areas with a large tidal range (typically more than 6 m between high and low water).
All these locations are shallow, narrowing rivers or fjords in which water is funneled via a broad bay. The funnel-like shape not only increases the height of the tide, but it can also decrease the duration of the flood tide down to a point where the flood appears as a sudden increase in the water level. The rising tide may force the tidal wave-front to move faster that a shallow water wave can propagate into water of that depth:<br>
T=L/(c+u)<br>
T = wave period<br>
L = wave length<br>
c = wave speed<br>
u = speed of current<br>
If the current flows counter the direction of wave propagation, then L will increase and the wave will get shorter and higher (upto the point of breaking).
Bore tides come in after extreme minus low tides created by the full or new moon (Chanson, 2004).
Bores take on various forms, ranging from a single breaking wavefront —like a shock wave — to ‘undular bores’ comprising a smooth wavefront followed by a train of secondary waves (whelps). Large bores can be dangerous for shipping.
Rivers that do have a tidal bore include the Amazon and Orinoco Rivers, in South America, the Hoogly River in the Ganges-Brahmaputra delta, several rivers in the UK, and rivers draining into the Bay of Fundy. The largest tidal bore occurs in the Qiantang River in China, it is 9m high and travels at 40 km/hr.
Tidal bores have distinct influence on sediment transport. The arrival of the borefront is associated with intense bed shear stress and bed scour. Suspended sediment is advected upwards in the wake of the tidal bore. This phase is associated with turbulent structure. The suspension of sediment is sustained by wave motion for several minutes to half an hour after the bore has passed (Chanson, 2004).
S
An equilibrium beach profile results from steady modest wave forcing during the summer. Summer wave conditions move sand onto the beach, widening its profile.
Winter storm waves move sand offshore (see assocated animation.Summer and winter beach profiles are expressions of the seasonal cycle of wave energy. +
W
An equilibrium winter beach profile results from more intense wave forcing during the winter. High winter wave conditions move sand away from the beach, cutting a wave platform. Unusually large storms may move all sands into deep water and leave skinny beaches for the early summer season.
Summer waves move sand back onshore (see associated animation) both summer and winter beach profiles are expressions of the seasonal cycle of wave energy. +
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Applied Model: WBMsed +
O
Barnhart, K., Miller, C.R., Overeem, I., Kay. J., 2015. Mapping the future expansion of Arctic open water. Nature Climate Change. 2 November 2015. +
B
Barrier Islands migrate over the shelf in response to sea level changes. The island first progrades outward, during sea level fall and then retrogrades when sea level is coming up again.
A elaborate discussion on classification can be found here:
http://science.howstuffworks.com/environmental/conservation/issues/barrier-island.htm +
W
Based on observed data +
