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Risk and Disasters Exam Review.docx

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Wilfrid Laurier University
Rob Milne

Risk and Disasters Exam Review Landslides  Result of changes in the forces of slope  Driving forces include uplift and erosion which cause rock to move faster down slope  Resisting forces act as friction force against the motion of rock materials  Movement o Fall  Lands at the base of the slope  Triggered by vibrations, ice or vegetation o Slide  Movement in contact with underlying surface  Eg. Rockslide o Flow  Liquid movement in water or sometimes air  Mass breaks up and flows during movement  Eg. Mudflow  Distribution in Canada o Common in mountainous areas o St. Lawrence lowland and B.C, Yukon and Alberta river valleys o Lacustrine, marine silts, clays, cretaceous shales and quaternary volcanic rock are materials prone to landslides  Factors that increase landslides o Urbanization and development o Tree cutting o Changing climate patterns  Prediction and warning o Slopes and seismic activity  Steepened slopes enhance seismic activity o Geology and structure  Rocks weakened by water are at risk o Surface water build up  Springs, pools and standing water o Topographic and vegetation features o Creep  Techniques to prevent earthquakes o Slope drainage  Capture runoff and take away from slope o Slope reduction  Reduce instability  Remove failing material o Engineering to resist movement  Concrete or crushed rock to reduce erosion o Engineering to mitigate damage  Netting, wired fencing, tunnels and rock sheds Floods  Drainage basin o Drained by a single stream o Each stream has its own drainage basin that collects rain and snow o Large river basins are made up of hundreds of watersheds drained by smaller streams  Flash floods o Associated with intense rains o Account for the most deaths o Unpredictable  Regional floods o Cover large flat areas o Occur following periods of prolonged rainfall or snowmelt  Discharge o Volume of water that moves through a cross-section of a river per unit of time  Channel patterns o Braided  Larger number of intersecting channels o Anastomosing  Two or more channels that branch and reconnect o Meandering  Single channel like a snake  Hydrographs o Made using recording gauges o Continuous record of water level is obtained and used to produce a graph  Flood prediction o Helps to determine frequency of flooding o Planning and land use are often dependent on the prediction intervals of flood events o Bigger floods in longer return intervals  Magnitude and frequency o Smaller floods produced by less intense storms  Recurrence interval o Determined by R = (N+1) M  Channelization o Modification of channel o Occurs in urban areas where the stream is fitted to built structures o Can increase the possibly of a flash flood and the frequency Wildfires  Causes o Natural  Lightening o Human  Intention and accident  Limiting factors o Fuel o Oxygen o Heat  Phases o Pre-ignition  Temperature and water favor ignition o Combustion  Ignition can be caused by lightening, volcanic activity or humans  Combustion liberates energy and its dependent on a fuel source o Heat transfer  Conduction  Radiation  Convection  Role of the wind o Cold fronts or large winds help produce large wildfires o Localization winds with high pressure may move the first down mountain sides o Fires are encouraged by warm dry wind with low humidity o Cooler winds sucked into the base of the fire and growth continues  Fire maps o Based on current and anticipated weather o Related maps determine lightening ignition, potential for wildfire growth and weather maps  Ecological role of fire in the forest o When lightening hits dry fuels, grass the result is fire o Life giving force o Many species depend on fire o Help to produce new seedlings o Natives use fires to burn their crops and promote growth of newer crops  Management strategies o Education o Codes and regulations o Fire insurance o Con
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