ice jam mechanics and its definition

8/4/2019 Ice Jam Mechanics and Its Definition

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1. Ice jam mechanics and its definitiona) An ice dam (or ice jam) occurs when water builds up behind a blockage of ice. Ice dams

can occur in various ways.

b) An accumulation of broken river ice caught in a narrow channel, frequently producinglocal floods during a spring breakup. Fields of lake or sea ice thawed loose from the

shores in early spring, and blown against the shore, sometimes exerting great pressure.

2. What are they? ExplanationAn ice jam is a stationary accumulation of fragmented ice or frazil that restricts

flow. This phenomenon can be seen in most of the colder parts and other regions in the

higher latitude, southern and northern hemisphere. Winter can leave a deep cover of snow

on the ground and ice on rivers .When the weather warms up and the ice in rivers begins

to melt, it breaks into pieces that float down the river .At the same time, water from

melting snow flows into rivers, causing floods .As large chunks of ice float downstream,

they can pile up near narrow passages or obstructions such as bridges, forming an icedam .Water that backs up behind such ice dams can cause flooding upstream backwater.

Orange color indicate back water

Ice jams


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Mechanism of occurrence

Ice jams occurs when warm temperatures and heavy rain (heat carried by rain droplet)

cause snow to melt rapidly. Snow melt combined with heavy rains can cause frozen

rivers to swell, which breaks the ice layer on top of the river. The ice layer often breaks

into large chunks, which float downstream and often pile up near narrowpassages/constriction, bridges and dams, creates backwater upstream .Interference with

the smooth flow or passage of water.

3. Similarities and analogiesa. Beaver pond

The beaver is a primarily nocturnal, large, semi aquatic rodent.Beavers are known for

building dams, canals, and lodges. Their colonies create one or more dams to provide still,

deep water to protect against predators, and to float food and building material.

Brewer Woods beaver pond

b. Log jamLog jam is an accumulation of logs and debris along the river resulting from the

logging activities. It often becomes problems and causes a lot of environmental issues

when logs are not sent down through the stream in a proper way. This phenomenon

can be seen in East Malaysias rivers.

Log jam


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c. Rubbish/garbage jam

d. Roof ice jamAn ice dam, on a smaller scale, on roof .An ice dam can occur when snow

accumulates on the slanted roof of a house with inadequate insulation and ventilation

in the attic .Warm heat from inside the building rises to the roof to melt the

accumulated snow.Melted water flows down the roof, under the blanket of snow, onto

the eave and into the gutter, where colder conditions on the overhang cause it to

freeze again and eventually, ice accumulates along the eave and in the gutter .Snow

that melts later cannot drain properly through the ice on the eave and in the gutter:

result in:

a. Leaking roof .b. Wet, ineffective insulation.c. Stained or cracked plaster or drywall.d. Rotting timber.e. Stained, blistered or peeling paint.Under extreme conditions, with heavy snow and severe cold, almost any house

can have an ice dam, whereas a house that is poorly insulated and ventilated will have

ice dams during normal winter weather.Giant icicles hanging from the eave are one

indication of a poorly insulated, poorly ventilated attic

4. what are their impacts on waterway?a) Obstruct smooth passage of water .b) Cause backwater effect.c) Force on piers in rivers.d) Environmental stench/odor/ill sights.


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e) Safety issue.f) Sudden burst of the ice or log jam cause dam breach type of flow: exceptional

high flow peak within a short time: hazard to downstream like quake lakes.

References:

1. http://books.google.com.my/books?id=k-NGKtJX4JoC&pg=PA21&lpg=PA21&dq=ice+jam+mechanics&source=bl&ots=ohSNM

_thln&sig=Hz7O8sfrUdDSLNAj_DjdQUdHN-

o&hl=en&ei=1vNXTfqTBomHrAfnqoixBw&sa=X&oi=book_result&ct=result&resnum

=5&ved=0CDwQ6AEwBA#v=onepage&q=ice%20jam%20mechanics&f=false

ice jam mechanics and its definition

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