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_____ forms in supercooled, turbulent, fast flowing water.
Frazil Ice Evolution
1. Forms spontaneously throughout depth in ________, _______ water.
2. Frazil will ____to form _____
3. When large, slush floats to surface and become ______
- supercooled, turbulent
- floculate, frazil slush
- Frazil pans (pancake ice)
Frazil Pans combine to form _____
Rafts and pans reduce water surface area and decrease rate of _______, and once it ceases, ______ is no longer possible, and _____ becomes likely
- frazil production
Spots where bridging is likely to occur
- - Tight bends
- - Bridge constrictions
- - Channel Constrictions (border ice)
If accumulation of rafts and pans is edge to edge, ______, forms.
juxtaposed ice cover
When drag force and ice weight collapse juxtaposed ice cover, ______ forms. This can result in _____, if it does it is called ______
- hummocky ice cover
- Freeze up ice jam
_____occurs when _____ adheres to the bed, is anchored there by weight of rocks. This is very bad for _____.
The ____ nature of frazil lets it pick up sediment and vegetation from the bed even before the ___ float to the surface.
In ____ reaches where ice cover does not form, _____ will continue throughout winter
When frazil accumulates at the end of steep reach, _____ form
When frazil production stops, freezing of ______ in the slush creates thick ice cover. Then further heat loss causes ______, which occurs in long, vertically oreiented crystals known as _________
- Pore water
- Thermal ice growth
- columnar ice
When snow weighs down ice cover, water seeps through cracks and ____ is formed
_____ is a problem for culverts , and results in ______.
Breakup is influenced by ______ and _______ processes, which dictate the ______ and _____ of river ice breakup
- thermal, dynamic
- nature, severity
In Thermal breakup, _____ influences are negligible. The important Meterological factors are _______ and _______.
- solar insulation and warm overlying air
3 Stages of Thermal Breakup
- 1. Snowmelt on ice cover
- 2. Development of open water leads
- 3. Thermal deterioration of ice cover
Snowmelt on ice cover
reduces its surface ______ and permits _____ to get into ice
Development of open water leads
Form along _____ where water is _____, allow a lot of ____ to enter flow and warmed water melts ice from ______
- sun's energy
Thermal deterioration of ice cover
Occurs at ______ rate as surface albedo _____
______ occurs because ice melts first at crystal ______. This form of ice has negligible _____
- Candle Ice
______ retains its _____ longer in thermal deterioration process
- Decaying frazil ice
Dynamic Breakup is strongly influenced by ______ factors, usually due to a large ________. An ______ will form if the ice run is arrested.
- snowmelt runoff event
- ice jam
6 Stages of Dynamic Breakup
- 1. Development & Overflow of open water leads
- 2. Hinge Cracks & Border Ice inundation
- 3. Transverse Cracking
- 4. Ice Clearing
- 5. Ice run
- 6. Ice Jam (potentially)
Overflow from open leads
rapidly rising water levels
water lifts center ice, cracks from ____ to banks, ______ melts quickally
Transverse cracking is _______ to flow
Ice Clearing and Ice Run - Ice begins to move, overcomes ________
Ice jams form when ice is stopped (island, bridge, bend), ______ results. When released causes another _____
Ice jam _____ leave behind ______, which can persist for many weeks
In the Canadian prairies, the shallow snow cover generates as much as ____ of the annual surface runoff. In higher elevations, snowfall can account for up to ____ of the annual water supply. The proportion of snowfall over total precipitation increases with _______.
I central Alberta, about ____ of the total precipitation comes as snowfall. The ration increases to about ____ in NWT and in the high Arctic, the ratio can be as high as _____. eg: ____ NWT
Important physiographoc and climate factors that influence distribution of snow are:
- orographic features
- precipitation amount
In open environments, effects of ____ and ____scale differences create varying ________ in vegetation and terrain
- meso and micro
- accumulation patterns
Most studies show greater snow accumulation in ______ than in ______. Most of the difference develops _____ storms, not _____ storms. _______ and subsequent _______ are major factors.
- during, not between
Snow intercepted by the forest canopy can either ______ or fall to the ______.
4 methods of determining SWE
- 1. Snow board
- 2. Snow sampler
- 3. Snow pillow
- 4. Snow gauges
The typical density of newly fallen snow is about ____kg/m3, but this _____ as new snow falls on top of it and compresses it, or as _____ and ______ of melt water 'toughens' it.
- wind & refreezing
What is sublimation?
Form of evaporation of snow/ice, which is transformed into water vapor under warm/windy conditions.
How does snow pillow work? What is its advantage?
Weight of snow on 3m platform causes antifreeze to rise up standpipe, indicating SWE.
Can automate measurments
Why does snow board only measure incremental depths?
To reduce errors caused by increasing density due to increasing layers of snow.
The standard snow gauge suffers from _______, which can be rectified using an _______ around the gauge.
The effects of _____ on accumulation and distribution of snowpack are most pronounced in open environments.
Sublimation losses involves both the latent heat of _____ (333kJ/kg) and the latent heat of ______(2501kJ/kg).
What is a snowpack?
Medium of air, water, ice, layers of different types of snow.
Snowpack albedo _____ with time, but snow density and grain size _____ with time.
Energy sources for snowmelt
- solar radiation
- longwave radiation
- convective or sensible heat flux
- vapour condensation
- advected heat from rainfall
Techniques to estimate snowmelt
- 1. 1D energy budget method
- 2. Degree day/temperature index method
- 3. Net shortwave radiation method
River ice reduces the __________. River ice approximately _____ the wetted perimeter for high _______ channels.
- active flow area
- aspect ratio
For same discharge, ice covered channel will have _____ water level than it would under ______ open water conditions.
Effects of flow on ice caused by under turning of pans and consolidation or shoving
- thicker ice cover
- rougher ice cover
- unsteady flow
If there is only border ice (partial ice cover), scenario is similar to __________.
Aquifer - geologic formation, yields water, stored in _______
Confined aquifer - relatively ______ zones, made of ____ and _____.
Unconfined aquifer - has ________, water table varies
Fractured aquifer - rocks, groundwater in _____, ______, ______
- impermeable, clay, bedrock
- free water surface
- cracks. joints. fracture
Well in a confined aquifer is called an ________, water rises higher then aquifer due to _________.
- Artesian Well
- confining pressure
Isotropy - permiability wrt ______
homogeneity - permeability wrt _______
What is bankfull stage?
What is the best indicator?
Stage at which water starts to flow over the flood plain.
The flat active flood plan surface. Use regional curves to help determine.
What are supplementary indicators of bankfull stage.
- -point bars
- -slope of bank
How long of a reach is needed to examine bankfull stage?
20 channel widths
Why is bankfull stage important?
- -determines when a flood occurs
- -stage where most sediment transport happens
- -governs channel formation.
Streamflow discharge measurement steps
- 1. 20-25 panels (>5% of flow)
- 2. determine Vavg of panels (average of 0.2d & 0.8d, or just 0.6d if small) using standard price current meter
- 3. sum discharges (Q=ΣVavg*area)
Uses _______ or _______ methods. All measurements tied to a ______ ________. Also need to consider __________.
- 1D analysis or 2D modeling
- common datum
- Resistance (mannings n)