Gestion des Risques Naturels

• Effective natural risk management can prevent dangers from becoming major catastrophes and further reduce the impact of disasters.

SGU and the Natural Risk Management Cycle: Prevention and Mitigation

• Inventory, tracking, detection, strike trajectory identification, and planning software are technological tools that can be used for natural risk prevention and mitigation.
• SGU can electronically provide commercial vehicle drivers with route forecasting services to ensure tracking along planned travel routes.

SGU and the Natural Risk Management Cycle: Intervention and restoration

• The intervention phase of the Natural Risk Management Cycle involves mobilizing emergency services to provide immediate assistance to people affected by disasters.
• The restoration, in the broad sense, covers the questions and decisions that must be taken after the initial needs have been settled following the catastrophe.
• SGU technology supports intervention and restoration efforts through: Programming and coordination software.
• Software can simultaneously monitor and coordinate interventions (search and rescue operations, emergency medical assistance, evacuation, and emergency communication to the public) to make the intervention process more effective, structured, and organized.
• Many sensors deployed on the infrastructure can provide an early warning system to identify large-scale emergencies, including natural or man-made technological disasters.
• Early warning systems monitor alert and guidance systems, computer sensors and monitoring systems, field reports, and emergency information call systems.
• Intervention management includes tracking emergency vehicle fleets equipped with automatic vehicle location technology and two-way communications between vehicles and dispatchers.
• Integration with traffic management systems allows for emergency information to obtained and distributed to public and private organizations and to the public.
• Evacuations often require coordinated emergency intervention involving many organizations, emergency rescue centers, and intervention plans.
• Various communication technologies can support evacuation management and various traffic transits..
• integration with traffic and transit management systems allows for rapid dissemination of emergency information to public and private organizations and to the moving public.
• This communication and cooperation also uses the diversity of information dissemination capabilities to provide travelers with emergency information.
• The Centre d'Opération d'Urgence (EOC) requires society engagement at all levels for managing emergency measures.
• This includes all citizens, localities, municipalities, administration, emergency intervention agents such as firefighters and health personnel, the private sector, volunteers, the academic world and international allies.
• Good partnerships based on collaboration, coordination and effective communication are an indispensable component of emergency management systems.
• Emergency Management requires collaboration, coordination and integration to promote complementary measures by all partners to promote timely and effective measures for prevention and preparedness, intervention and restoration to effectively face catastrophes.
• Floods are more or less exceptional phenomena characterized by the temporary submersion of land.
• Submersion can have different causes, including precipitation, fluvial and torrential floods, meteorological phenomena, and technological hazards.
• Submersion can be caused by rising groundwater, earthquakes, or landslides (causing tsunamis), potentially leading to inundation by river overflow, rising groundwater, runoff, or marine overflow.
• A protection system corresponds to the set of structures and elements of the environment intended to protect a naturally floodable territory against floods.
• Flood protection can be considered either absolute (absence of flooding up to a defined hydrological level) or relative (reduction of the risk of flooding in terms of probability, intensity, duration and / or arrival time).
• A protection system takes place within hydrographic or coastal systems to modify local hydraulic behavior during events, for the interest of an area that is naturally subject to flooding.
• Complete protection is associated with natural event probabilities on the order of 10-2 (variable between 10-1 and 5.10-3, more rarely 10-3).
• For the integrated analysis of flood risk, we speak of SPR (source, pathway, receptors), a model used in other areas.
• In applying this model to the risk of flooding of dike systems, the pathway corresponds to the system of protection.
• Actions are any phenomena that can apply to a structure and cause movements, deformations, or erosion on or within a structure, or effects on internal hydraulics.
• The term solicitation is used to designate actions and effects on structures, in dikes and hydraulic structures.
• Hydraulic actions on structures result primarily from contact with aquatic environments and various types of effects leading to deterioration mechanisms.
• Water levels cause pore water pressures, internal water flows, and shear stresses, which lead to translational landslides and internal erosion.
• Currents or flows on the water side of a structure cause shear stresses, leading to internal erosion.
• Currents or flows of overtopping produce removal stresses, external erosion of the pavement and undermining and external erosion by overflow waves.
• The system of protection is the addition of a system of protection and the area it protects from flooding; it must be composed solely of works.
• The study of dangers must cover all the works that make up a containment system, including an in-depth diagnosis of the condition of the works and taking into account the behavior of natural elements.
• The system of containment could be made of dikes, an engineered creation with another use than protection, or natural elements.
• The areas in contact with the protection system are aquatic environments.
• The analysis of the risk of flooding of an embanked system corresponds to the analysis of the risk of flooding, on the part of the water environments considered, of the protected zone.
• The perimeter of a protection system is considered hydraulically coherent when it integrates all of the effectively protected zone, considering the topography and the hydrological context, and that it allows the complete analysis of all flooding scenarios likely to impact this zone.
• Actions correspond to phenomena that can apply to a structure and cause movements or deformations or erosions, or effects on internal hydraulics.
• The actions related to the hydraulic behavior of water environments result from contact of the protection system with the aquatic environment and can have various types of effects causing deterioration mechanisms.
• Different types of hydraulic actions on the protection system can be caused by a number of external factors.
• A number of actions depend of human activity or natural events, and cause different types of damage to the system.
• Dikes provide protection against floods, but are mainly made of embankment structures although rigid structures are also known.
• The mechanisms of degradation and rupture of rigid structures are the overall sliding of the structure on its foundation, overturning of the structure, sliding or overturning of an upper part of the structure, external abrasion of the structure, and chemical phenomena affecting concretes or reinforcements.
• Breaches in the dike, open gaps between the body of water and the protected, trigger inundation within protected zones to occur when flood protection has been achieved.
• The main function of a protection system is, most often, to protect a naturally floodable territory against floods, while secondary functions include protecting against erosions or allowing for the maintenance or surveillance of maritime structures.
• In a river environment, a protection system generally primarily protects against flooding caused by floods from a stream or perhaps also of one or more tributaries.
• The morphology of the river can therefore generally be respected, ensuring an implementation of dikes set back from the low water bed.
• Coastal marine protection systems are often centered on controlling the effects of sea action on the morphology of the coastal fringe, with the objective of fixing the coastline.
• They can also assist with land reclamation, such as in coastal polders.
• The main function of torrential protection systems is to protect the area exposed to torrential floods, by preventing the torrent from overflowing.
• Systems of protection against floods are composed of dikes, and other works having this role, and natural elements.
• A system of protection can be broken down into elements having specific hydraulic functions.
• The capacity of a system of protection and its elements to fulfill their functions depends on the capacity of its elements to resist degradation processes.
• Configuration and constitution of protection systems generally vary depending on aquatic environments in which they are implemented.
• In general, for the analysis of flood risk, we speak of SPR (source, pathway, receptors).
• The range of infrastructure and structures can include levees, dikes, floodwalls, berms, pump stations, temporary structures, bridges, or roads.
• System designs can include, enclosed, and open systems; Branched and simple linear systems, and hydraulic boxes.
• Incorporate natural topographic element, such as dunes, mounds, rocky promontories and other natural topography to protect systems against water events.
• The study of hazards must cover all the works that make up a containment system, including a diagnosis of the condition of the works and considering the behavior of natural and human elements.
• There are many varieties of levee structures.
• These are the building blocks of water-based flood risk and are usually built with multiple protective measures.
• Impermeable solutions are used, while maintaining structural safety, depending on terrain or surface type.
• Advances in knowledge and technology have gradually increased the size of structures up to current records, to address increasing needs for water management.
• The French colonial authorities saw Morocco, with its potential for production, as a back-up to their agricultural interests.
• The authorities began the construction of some large dams in the 1920s and this continued in later years to provide potable water, water for irrigation, and electricity.
• Economic benefits can be seen from a dam construction project through the hiring of local workers or orders placed with subcontractors.
• Positive regional and national benefits are also seen over time through electricity production, irrigation, or the provision of potable water.
• Dams allow for the recreational use and creation of artificial beaches and water based activities.
• The fight against floods and droughts and in response to the growing global demand for water, require constructing more dams in many places around the world.
• Managing water is of growing importance, and it is predicted the global demand could grow by 2-3% per year in the years ahead.
• Hydroelectricity from dams is key: it is a clean and renewable source of energy, and reduces reliance on polluting sources.
• Dams and water reservoirs permit effective harnessing and control when managing flood damages.
• In the absence of dams, water levels that are used for rivers, lakes and other uses, becomes less potable due to natural variability and weather.
• Storing water provides the greatest gains in providing access to clean water, especially where underground water levels are heavily exploited.
• Earthern dams can compress due to poor soil foundations, and may require strengthening.
• Different kinds of soil are used to produce water.
• Earth dams have three basic types: homogenous, core dams, and masque dams.
• Earth dams present the advantage of being able to rest on foundations of poor compression quality and the clay protects the interior of a structure.
• As the name suggests, this type of dam opposes it's weight to hold water to stop leakage.
• Concrete presents the advantage, in particular, of authorizing the construction of more solid works with two basic types: weight-based dams and arch-based dams
• The design can also influence the material composition.
• Damns with multiple supports use supports inside the dams or external supports to support the water.
• Canals can assist river navigation, by raising the existing height of rivers by a few meters to allow for navigable channels.
• In order to counter effects such as high rain, the canal must sometimes overflow the river bed itself if needed.
• All dams possess the capacity to infiltrate water, both clay and concrete dams.
• Water can pervade dams while also permeating their foundations.
• The ability to draw off water from the top or bottom will help mitigate many problems.
• In concrete dams, the shielding will be strengthened at a more high level and at the same time, the drainage pipes that will drain the infiltrations will be integrated.
• In the foundations: cement injections and drainage holes can be strategically placed to reduce the amount of water and to divert the water that washes into the sediment.
• Flood management can affect the choice of the type of dam, depending on the hydrological and topographical conditions of the site concerned.
• In effect, an earth dam can more difficultly integrate a spillway, particularly with greatest largest structures.
• In addition, an earth dam proves more sensitive to the submersion during building than a concrete dam.
• When the sluice gate moves to its base, water moves further into the bottom surface and also becomes non traversable.