Snow Emergencies

Snow Emergencies

David Alexander University College London

Blizzard: • temperatures usually -10oC or lower • snow drifts caused by strong winds • winds of at least 30 knots (55 km/hr)

Severe blizzard: • temperatures of -12oC or lower • winds of at least 40 knots (75 km/hr) • visibility effectively zero.

Classification of the level of interruption of normal socio-economic activities (Rooney 1967): • internal: restricted to the city • external: between city and its region.

Snowfalls in urban and metropolitan areas

Level Interruption Description

V Minimal Insignificant effects, no attention from the mass media

IV Nuisance Speed of traffic reduced, some absences from school

III Inconvenience Road accidents increase, risks for motorists, rural residents do not come to town, etc.

II Paralysis Absenteeism, delays, road traffic accidents, abandoned vehicles

I Total

paralysis

Emergency services at full alert, closure of roads, schools, airports, etc.

Classification of the level of interruption of normal socio-economic activities

...annual accumulations of snow: • depth of accumulation • the more snow falls in a year, the more incidences of disrution at levels III-V • level I disruption (total paralysis) is not correlated with annual accumulation • the more snowfalls occur, the greater the level of municipal preparedness.

The level of disruption of normal activities caused by snowfall is related to...

The impact of individual snowstorms depends on: • when they happen (day, hour) • intensity of precipitation • depth of snow accumulation • wind speed.

The level of disruption caused by snowfall

• at higher temperatures snow becomes denser and stickier

• if wind speeds exceed 25km/hr the snow forms drifts.

The level of disruption caused by snowfall

• a year with more frequent snowfalls

• a year with heavy and prolonged storms

• big snowfalls at the end of the season when the snow clearance budget is used up.

Problem: a possible budget shortfall

• road salt and grit

• overtime payments to workers

• maintenance and repair of vehicles

• improvement and replacement of fleet

• costs of interruption of activities.

Planning and funding the operations

Snow emergency planning

• meteorological services

• road surveillance cameras

• field reports from operatives

• overflights (helicopter recce).

Snow emergency monitoring systems

• snowfall in relation to transportation networks

• extent of snow disruption at different altitudes above sea level.

The planning process:-

...the snowfall occurs suddenly, rapidly and with little or no warning?

...the snowfall occurs at the worst possible time regarding socio- economic activities (rush hour on Friday just before Christmas)?.

"What if?" scenarios

...electricity supplies are interrupted or hours or days?

...strong winds cause massive drifting?

...many people (or animals) are isolated?.

"What if?" scenarios

Who decides? • e.g. on closures Who monitors? • e.g. meteorological and road conditions Who commands (whom)? • e.g. on rescue, on snow clearance Who communicates? • e.g. to mass media.

• transportation: roads, railways, airports • schools and colleges • shops, offices, factories.

Co-ordination and diffusion of information on closures

• risks • closures • advice on what to do • radio and television links.

Role of the civil protection service as a collector and disseminator of

information on the evolving situation

• how to rescue stranded livestock

• delivery of urgent life-saving supplies

• urgent movement of sick & injured people

• where to hold heavy goods vehicles.

Some specific problems

At what point does a snow emergency cease to be a transient interruption and become a serious problem of business continuity management?.

A question to answer:-

• an accumulation of at least 0.64 cm of ice on exposed surfaces

• precipitation at temperatures that oscillate around 0oC

• roads and pavements very dangerous

• fall of branches from trees

• fall of pylons and utility poles.

Ice storms

Temperature (degrees C) -4 -2 0 2 4

1 km

2 km

3 km Snow

Freezing rain

Rain

Sleet

Altitude

Formation of precipitation at different altitudes a.s.l.

• 80 hours of continuous freezing rain

• 1,000 pylons and 35,000 poles collapse

• millions of trees killed

• 150,000 people without electricity for more than three weeks in Québec.

Ice storm in SE Canada/NE USA January 1998

Ice storm in SE Canada/NE USA January 1998

My house in Amherst, Mass.

Further reading:- http://www.ukroadsliaisongroup.org/ en/utilities/document-summary.cfm? docid=7E330478-F948-42 A3-93F8B3A4862AA655

Thank you for listening!

david.alexander@ucl.ac.uk emergency-planning.blogspot.com www.slideshare.net/dealexander