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.
Snowfalls in urban and metropolitan areasClassification of the level of interruptionof normal socio-economic activities(Rooney 1967):• internal: restricted to the city• external: between city and its region.
Classification of the level of interruption of normal socio-economic activitiesLevel Interruption Description Insignificant effects, no attention V Minimal from the mass media Speed of traffic reduced, IV Nuisance some absences from school Road accidents increase, risks forIII Inconvenience motorists, rural residents do not come to town, etc. Absenteeism, delays, road traffic II Paralysis accidents, abandoned vehicles Emergency services at full alert, Total I closure of roads, schools, paralysis airports, etc.
The level of disruption of normal activities caused by snowfall is related to......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 caused by snowfall 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.
Problem: a possible budget shortfall• 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.
Planning and funding the operations• road salt and grit• overtime payments to workers• maintenance and repair of vehicles• improvement and replacement of fleet• costs of interruption of activities.
Snow emergency monitoring systems • meteorological services • road surveillance cameras • field reports from operatives • overflights (helicopter recce).
The planning process:-• snowfall in relation to transportation networks• extent of snow disruption at different altitudes above sea level.
"What if?" scenarios...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?.
Who decides?• e.g. on closuresWho monitors?• e.g. meteorological and road conditionsWho commands (whom)?• e.g. on rescue, on snow clearanceWho communicates?• e.g. to mass media.
Co-ordination and diffusionof information on closures• transportation: roads, railways, airports• schools and colleges• shops, offices, factories.
Role of the civil protection service as a collector and disseminator ofinformation on the evolving situation • risks • closures • advice on what to do • radio and television links.
Some specific problems• how to rescue stranded livestock• delivery of urgent life-saving supplies• urgent movement of sick & injured people• where to hold heavy goods vehicles.
A question to answer:-At what point does a snow emergency cease to be a transient interruption and become a serious problem of business continuity management?.
Ice storms• 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.
Formation of precipitation at different altitudes a.s.l. Altitude 3 km Snow 2 km Freezing rain Sleet 1 km Rain -4 -2 0 2 4 Temperature (degrees C)
Ice storm in SE Canada/NE USA January 1998• 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.