A megacity is usually
defined as a metropolitan area with a total population in excess of 10 million people. Some definitions also set a minimum
level for population
density (at least 2,000 persons/square km). A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis and metroplex are also applied later. Top ten megacities are tabulated
here as per the data 2013 April.
Administrations in the world’s largest
cities are often confronted with a multitude of key problems like high urban
densities, traffic congestion, energy inadequacy and managing sustainable
development and climate change. In the developing world, additional problems such as a
lack of basic services, illegal construction both within the city and in the
periphery, informal real estate markets, creation of slums, poor natural
hazards management in overpopulated areas, crime, water, soil and air pollution
leading to environmental degradation, land subsidence and poor governance
arrangements. These are within and surrounding megacity problems.
Megacities have large population that
every inhabitant depends on the rural areas for foods and beverage, water
supply, Electricity supply etc. Human resources for the factories and for
services required within cities are also depends on rural area. Most of the
resources are directly from rural areas or they have to come through these
countryside.
Linkage
Mega city is located either in the coastal side or inland but anyway it must have to link with rural areas. All the resources and goods to be transported to megacity from rural areas are very important so linkage between rural area and megacity is main point of consideration for existence of life in mega city. Following linkage chart shows some schematic flow:
Management of
the megacity consists the management of the supply of resources and energy
to the city, for that mainly following points are taken into consideration.
Infrastructure assets management
Railways
Bridges, retaining
walls
Energy management
Towers and transmission
lines
Pipelines
Logistics
Transportation system
Vehicle management
Environmental accounting for structures
Water supply management and food supply system
Public infrastructures have constructed for service to people by public funds. Infrastructures for
linkage of megacity to the rural areas are more important than the
infrastructures within mega city. For the logistic systems roads and railways
are basic for the management of vehicle routing and transportation.
FOCUS ON INFRASTRUCTURE ASSET MANAGEMENT.
Infrastructure asset
management deals for the management of the linkage highways and railways.
Stability of soil is more important for the stability of structures like road,
tunnels, railway, bridges etc. Vulnerability of these infrastructures also
covered the vulnerability caused to its vicinity. There are so many
settlements that we have to consider during the safety calculation of
infrastructures. Losses due to failure of infrastructure will cause
interruption of supply to megacity, diversion will cause loss of time and fuel
also increase environment pollution.
Problems on linkage
which have to cover under infrastructure asset management are:
- Landslides
- Deterioration of road surface
- Deterioration of bridges and culverts
- Blockage on tunnels
- Soil settlements
Landslide is the main
problem for the roads and railways that block fully on its operation, which may
cause due to the activities during construction, geological conditions, weather
etc. Other points are
mainly have to cover under periodic and routine maintenance can disturb
partially or no effect to traffic movement.
Risk and mitigation of problems
Landslides (landslips, the collapse and flow of earth,
mud and rock falls) often occur in times of bad weather (heavy rain, storms),
earthquakes, floods, avalanches or melting snow. It is thus as difficult to
distinguish between their causes and effects as it is to differentiate between
preventive and protective measures.The damage caused by a landslide varies
according to the phenomenon at the origin of the danger and can affect whole
regions through, for example, flooding or rivers of mud,or very limited areas
as when rock slides or falls occur.A localized event can also have widespread
consequences especially if it disrupts transport links (roads, rail, and cable
cars) or damages the infrastructure (important buildings, electricity grids,
telecommunication networks, conduits, pipe works and reservoirs for water, gas,
toxic and polluting substances).Landslides can also affect the safety of
power houses and hydro power dams or cause the buildup of water behind unstable embankments thus threaten to the population and infrastructure in downstream.
Interruptions on road
Landslides can occur slowly or rapidly. They can
generally be predicted by observing areas known to be unstable and by taking
into account the meteorological conditions (bad weather).
Preventive measures consist of developments and constructions intended to avoid or at least limit landslides through stabilizing work: terracing, drainage anchoring, deep injections into the soil or by the construction of retaining dikes to hold back or divert landslides, tunnels, shafts, etc. Plantation in unstable areas is also an efficient preventive measure.As regards long term security measures it is important that legislation on land development requires a systematic appraisal of the potential natural dangers. Before establishing residential areas and granting planning permission for buildings in vicinity of highways and railways, vulnerability must be taken into account.These measures will be complemented by the constant monitoring of unstable areas and by an obligation to upkeep forests and vegetation and to maintain high altitude waterways (water falls, silting basins, dikes etc.).The damaging effects of landslides will primarily be avoided or limited by taking the following preventive and protective measures:
Preventive measures consist of developments and constructions intended to avoid or at least limit landslides through stabilizing work: terracing, drainage anchoring, deep injections into the soil or by the construction of retaining dikes to hold back or divert landslides, tunnels, shafts, etc. Plantation in unstable areas is also an efficient preventive measure.As regards long term security measures it is important that legislation on land development requires a systematic appraisal of the potential natural dangers. Before establishing residential areas and granting planning permission for buildings in vicinity of highways and railways, vulnerability must be taken into account.These measures will be complemented by the constant monitoring of unstable areas and by an obligation to upkeep forests and vegetation and to maintain high altitude waterways (water falls, silting basins, dikes etc.).The damaging effects of landslides will primarily be avoided or limited by taking the following preventive and protective measures:
- Monitoring (observatories or specialist institutes) constantly or randomly unstable areas representing a major threat.
- Establishing one or several information and alarm centers to inform the authorities and the public.
- Imposing building restrictions, forbidding people from staying in restricted areas and banning traffic on certain routes (road, rail, etc.)
- Erecting buildings and developing infrastructures that will prevent or limit landslides and protect the population.
- Planning the evacuation of populations eventually at risk.
- Establishing well equipped and trained disaster management and rescue teams.
Preventive measures
For undisturbed life on megacity, we have to manage
the infrastructures that use for linkage to rural area. In contest of
infrastructure management we have to do some risk analysis and implement the
preventive measures to reduce risks of landslide and other hazards, which must
have to be a part in the management of megacity.
