Coastal
Hazards are physical phenomena that expose a coastal area to risk of property
damage, loss of life and environmental degradation. The risk that a natural
hazard poses is considered by estimating the impact that it would have on the
people, services, facilities, and structures in a coastal community. Risk is
typically defined as “probability of an event x consequence” and the greater
the frequency and/or impacts, the greater the risk.
Coastal
hazards are caused by different mechanisms, producing ’drivers‘ that directly
affect the coast. Coastal hazards can be grouped into categories:
·
coastal
inundation (or flooding)
·
coastal
erosion (cut-back) and accretion (too much sediment)
·
recreational
and maritime hazards.
Coastal-hazard
drivers come from storms, winds, sea-level changes due to climate variability
(for example, seasonal and El Niño), and earthquakes that rupture the seabed
(which can create tsunamis).
1. Flooding
Flooding may
result from a coastal storm, dam break, or a heavy rainfall within the coastal
watershed. Development continues to intensify within flood-prone and marginal
areas along the coast or in coastal watersheds. Protecting floodplains
preserves the natural functions of ecosystems and also helps prevent loss of
life and property from damaging floods.
2. Lake Levels
Low water
levels present a hazard to navigation and water supply intakes, and limit
riparian landowners’ access to the lake. High lake levels cause widespread
flooding and bluff erosion. During these high water periods, storm surge and
storm waves can cause severe property damage and shoreline erosion. Areas on
the Great Lakes that experience chronic flood and erosion damages were
typically constructed during times of low lake levels.
3. Storms
The main
threats associated with these hazards are storm surge, high winds, heavy rain
and flooding, as well as tornadoes. Winter storms can produce rough lake conditions,
coastal flooding, and beach erosion. Strong winter storms are also responsible
for significant land losses around the Great Lakes.
4. Erosion
Coastal
erosion is a process whereby large storms, flooding, strong wave action and
human activities – such as inappropriate land use, alterations, and shore
protection structures – wear away beaches and bluffs during a flood or storm or
over a period of years. Erosion undermines and often destroys homes,
businesses, and public infrastructure and can have long-term economic and
social consequences.
Climate
change will affect three out of the five causes of coastal hazards. Even
tsunamis, which are generated by geological processes unaffected by climate
change, will eventually pose a slightly larger threat because they will ride on
top of a higher sea level.
To
understand the important role that the coast line paly here is an explanation. In
its natural state, the coast acts as a buffer to the dynamic ocean colliding
with a fixed landmass. The coast must at times absorb tremendous energy
generated by large waves, severe winds, storms, and tsunamis – and take the rap
over a very narrow buffer zone. Mostly, the coast absorbs this energy by
wave-breaking in shallower water and by either flexing through the movement of
large quantities of sand or gravel (causing beach erosion or accretion) or
providing a barrier, such as a cliff or sand dune, high enough for gravity to
halt the sea’s onslaught. When properties, infrastructure, and people get
caught up in this buffer zone, these natural coastal processes become hazards. https://www.niwa.co.nz/publications/wa/vol15-no3-september-2007/coastal-hazards-rising-problems
Since
Morocco has 3500 km (2174.8 miles) of coastal lines, coastal hazards are
common. Many areas face several damages mainly due to the lack of necessary
defense mechanism. Some of the country’s coastal land is located below the sea
level. the northeast of the country ( near a city named Nador) where many small
islands start disappearing under water. Another example, The Tangier coastal
strip of the northern coast of Morocco located at the western end of the Strait
of Gibraltar between the Mediterranean Sea and the Atlantic Ocean; is at risk
and that’s because the earthquakes that are generated from the tectonic plate
of the African and Eurasian one. Not only that, the 1 November 1755 event is
the most destructive tsunami ever reported along the Moroccan Atlantic coast.
It was caused by an earthquake of magnitude 8.5 in some places the water
penetrated more than 2000 m inland. The most recent tsunamis that were observed
in Morocco without appreciable damage are those of 25 November 1941, and of 28
February 1969. The 1941 tsunami was triggered by a Mw 8.3 strike-slip
earthquake in the Atlantic; the waves were recorded by the gauges in Casablanca
and Essaouira with maximum amplitudes of 25 (9.8 inch) and 45 cm (17.7 inches),
respectively.http://www.tandfonline.com/doi/full/10.1080/19475705.2013.858373
And in the
last couple of year, morocco have seen some storm surges that pushed the water
inland bringing with it debris from the sea, such as rocks from Crashing
violent waves that hit the coastline. In the early hours of Friday, February 3,
2014, the coast of Salé and Casablanca were hit by very high waves.
the wave height reached 9 meters (29.5 foot), submerging neighborhoods and coastal areas of Sale, Rabat, Mohammedia, Casablanca, El Jadida, Safi, and Agadir. These have caused significant damage to several houses on the coastal road. Following these huge waves, roads were completely covered with mud and sand blocking the traffic for several hours. As for the inhabitants of the districts submerged by the waves, they were quickly evacuated. fortunately, no lives were taken except property damages and complete chaos.
the wave height reached 9 meters (29.5 foot), submerging neighborhoods and coastal areas of Sale, Rabat, Mohammedia, Casablanca, El Jadida, Safi, and Agadir. These have caused significant damage to several houses on the coastal road. Following these huge waves, roads were completely covered with mud and sand blocking the traffic for several hours. As for the inhabitants of the districts submerged by the waves, they were quickly evacuated. fortunately, no lives were taken except property damages and complete chaos.
In the city
of Casablanca, which is the biggest city of Morocco, Coastal erosion and
submersion will be particularly affected by the sea level rise indirectly
provoked by global warming through the thermal expansion of water masses
(dilation) and the melting of the polar ice cap, and a study showed that an
overall sea level rise of 20cm by the year 2030. In the Casablanca region, the
coastal stretch exposed to a high risk of erosion or submersion will remain
approximately identical to the present situation, which is around 40km of
coastline. The sea level rise will however slightly increase the risk of
submersion of low-lying areas.
http://www.cmimarseille.org/sites/default/files/newsite/library/files/en//UD2_wk2_Study_Morocco_ExecutiveSummaryPhase1_EN.pdf
http://www.cmimarseille.org/sites/default/files/newsite/library/files/en//UD2_wk2_Study_Morocco_ExecutiveSummaryPhase1_EN.pdf
In an
attempt to limit this phenomenal, the Kingdom is launching multiple projects
that re-construct the shape of the most vulnerable coast line by creating
artificial islands and completely reshaping how the water is coming in contact
with the land by reinforcing the sea wall. In addition, the country is also conducting several study areas
that are potentially at risk, from forecasting system for waves and storm tide
levels, use of real-time monitoring to update emergency managers on storm tide,
waves, and tsunamis, developing models for estimating potential damage to the
built environment to guide decisions on risk. These study will result in having
a detailed map, Building classification based on primary (intrinsic) factors of
vulnerability, and Damage matrix obtained for building vulnerability derived
from the vulnerability functions.
