Coastal Protection
Coastal Protection
Measures aimed at protecting the coast against coastline retreat, thus
protecting housing, infrastructure, the coast and the hinterland from erosion often
at the expense of losing the beach and the dynamic coastal landscape. Coast
protection often consists of hard structures such as revetments or groynes.
Coastal protection is deemed necessary to protect the completed profile of the
reclaimed land. Coastal protection prevents erosion caused by wave, current, tide
and flooding by the open sea. On the other hand, coastal protection also protects
leaching of reclaimed material from the reclaimed land, which could occur
because of groundwater flow.
Why is coastal protection important?
The coast is a dynamic environment located where land, sea and air meet. Furthermore, the
coastal systems provide a wide range of functions including absorption of wave energies, nesting and
hatching of fauna, protection of fresh water or siting for recreational activities. However, migration of the
human population to the coast has turned coastal erosion into a problem of growing intensity.
The management of the risk of coastal erosion is really important. The changes in this natural
area can increase the risk of coastal flooding. It can also result in land loss, which is an issue for urban
and industrial areas, and nature reserves.
Coral reefs, mangroves, seagrasses, salt marshes, and sea ice act as natural buffers against
incoming waves. By protecting against storm damage, flooding, and erosion, these living habitats keep
people safe and can help mitigate economic loss of personal and public property, cultural landmarks
and natural resources.
Natural causes of coastal erosion
Cross-shore sand loss
• Breaching and over-wash. The loss of sand inland due to breaching and over-wash of a barrier island.
• Aeolian transport to the dunes. A wide vegetated dune area can trap fine sands carried inland from the beach by
onshore winds.
• Offshore sand loss under extreme wave and storm surge conditions. High energetic waves cause seaward
migration of breaker bars and high storm surges further cause an offshore movement of sand due to non-
equilibrium in the profile during the high surge. Sand that is transported sufficiently far offshore will not return to
the coast by wave-induced onshore transport under a milder wave climate.
Climate change
• Climate change impacts. Climate change will impact on coastal erosion in different ways. Here the focus is on
sea-level rise; other potential impacts are related to changes in meteorological conditions – wind, temperature
and precipitation.
Human causes of coastal erosion
Erosion due to decrease of fluvial sand supply
• Decrease of fluvial sand supply to the coastal zone is a common cause of coastal erosion. Reduction of
fluvial sand supply can result from different human interventions such as creation of reservoirs for power
production and irrigation purposes by the construction of river dams, deepening of navigation channels,
mining of river sand.
Sand and Coral Mining, and Maintenance Dredging
• The mining of sand and gravel along beaches and in the surf-zone will cause erosion by depleting the shore
of its sediment resources. In connection with maintenance dredging of tidal inlets, harbours, and navigation
channels, sand is very often lost from the littoral budget because the sand, unless otherwise regulated by
legislation, is normally dumped at deep water. Coral mining and other means of spoiling the protective coral
reefs, for example, fishing by the use of explosives or pollution, will also cause coastal erosion and beach
degradation. The protective function of the reef disappears and the production of carbonate sand stops.
Coastal erosion due to manmade structures
Coastal structures interfering with the littoral transport are the most common
cause of coastal erosion.
• Trapping of sand at the upstream side of the structure that reduces sand supply to the
adjacent shores. This causes mostly erosion at the lee side, but large structures may also
cause (initial) erosion on the upstream side.
• Loss of sand to deep water.
• Trapping of sand in entrance channels and outer harbours. Sand is often deposited in deep
water after being removed by dredging.
The structures, which may cause this type of erosion, are:
• Groynes and similar structures perpendicular to the shore. Groynes are normally built perpendicular to the
shoreline with the purpose of protecting a section of the shoreline by blocking (part) of the littoral transport, whereby sand is
accumulated on the upstream side of the groyne. However, sand trapping causes a deficit in the littoral drift budget, and this kind
of coast protection is always associated with corresponding erosion on the lee side of the structure. In other words, a groyne just
shifts the erosion problem to the downstream area. This is the reason that groynes are often built in long series along the
shoreline, a so-called groyne field.
• Ports. The primary purpose of a port is to provide safe mooring and navigation for the calling vessels but when built on the
shoreline it interferes with the littoral drift budget and the results are sedimentation and shoreline impact. Like a groyne, the
harbour moles of a port can block the littoral transport, by trapping sand at the updrift side in the form of an accumulating sand
sheet. The sedimentation that occurs at the harbour entrance in the case of sand bypass requires maintenance dredging and
deposition of the dredged sand. The result is a deficit in the littoral drift budget, which causes lee side erosion along the adjacent
shoreline. A port on the coast must therefore be designed such that sedimentation and coastal impact is minimal.
• Inlet jetties at tidal inlets and river mouths. Tidal inlets and river mouths are often by nature shallow and variable in
location, which makes them unsuitable for navigation. In order to improve navigation conditions and, to some extent, flushing
conditions, many tidal inlets and river inlets have regulated mouths. Regulated inlets are normally obstructions to the littoral
transport which means upstream sand accumulation along the upstream jetty, loss of sand due to sedimentation in the deepened
channel and the associated maintenance dredging. All in all, regulated inlets will very often cause lee side erosion problems.
• Detached Water breakers. Detached breakwaters are used as shore and coast protection measures. In general terms, a
detached breakwater is a coast-parallel structure located inside or close to the surf-zone.
PORTS
Inlet Jetties
Groynes
BREAKWATER
Coastal Protection Method
• Building a sea wall. A wall built at the edge of the coastline. Protects the base of cliffs, land and buildings
against erosion. Can prevent coastal flooding in some areas. Provides equal protection along frontage; Can be
designed to support a sea front development.
• Revetment. A revetment is a facing of stone, concrete units or slabs, etc., built to protect a scarp, the foot of a
cliff or a dune, a dike or a seawall against erosion by wave action, storm surge and currents. This is not as
strong as seawalls.
• Groynes. Shingle beach: any tidal range; Sand: micro-tidal only; Low net littoral drift; Low structures suitable for
low wave energy; Large mound type structures suitable for high wave energy. Allows for variable levels of
protection along frontage schemes to put coastal policies into practice.
• Detached Breakwater. A detached breakwater is a structure parallel, or close to parallel, to the coast, build
inside or outside the surf zone. Detached breakwaters are mainly built with two purposes, either to protect a
ship wharf from wave action or as a coast/shore protection measure. Allows for variable levels of protection
along frontage.
• Bulkhead. Bulkheads or seawalls are structures erected parallel to and near the high water mark
for the purpose of protecting adjacent uplands from the action of waves or currents.
• Gabions. Are steel mesh cages that are filled with rocks, concrete and sometimes aggregate, and
used to stabilize vulnerable areas, by absorbing wave energy.
• Sills. Low wave energy; Low and variable drift; Submerged with micro-tides, regularly exposed with
macro-tides. Provides equal protection along frontage; Can be designed to support a sea front
development.
SEAWALLS
REVETMENTS
GABIONS
BULKHEADS
Title Lorem Ipsum
LOREM IPSUM DOLOR SIT AMET, NUNC VIVERRA IMPERDIET ENIM. PELLENTESQUE HABITANT MORBI
CONSECTETUER ADIPISCING ELIT. FUSCE EST. VIVAMUS A TELLUS. TRISTIQUE SENECTUS ET NETUS.
*
Natural vegetation has a massive impact on a
riverbank. The plants form deep root systems
which help to hold soil in place and protect it from
being washed away.
*
Coir geotextile fabric consists of woven fibers of
coconut. The fabric is available in rolls that can be
rolled out over the surface of an embankment,
preventing soil erosion on newly graded slopes.
*
The advantages of geotextile:
*Simplicity of installation
*A fully biodegradable product
*Relatively low maintenance
A brush mattress, also known as live brush mat, is a
means protecting stream banks by combining live
brush cuttings, fascines (bundles of sticks or other
materials) and stakes to cover and stabilize stream
banks.
*
Advantages of this technique:
*Ideal for use along streams that receive plenty of
sunlight, which will help the cuttings quickly root
*Quick installation
*Fully biodegradable system
*Low maintenance
*
This system is somewhat less natural than the
others. Gabions combine the use of natural stone
with manufactured metal wires. The system
consists of pouches, baskets, or boxes made of
high-strength, double-twisted hexagonal mesh
filled with stone (or sometimes concrete rubble).
*
Gabion
Advantages of gabions:
*Can be installed underwater to "train"
streams to a desired path
*Very strong system that resists heavy water
flow
Hard armoring involves the layering of rocks along
the bank in order to protect it from water erosion.
This, however, leads to problems. Riprap causes
the speed of the current to increase because it
reduces friction points.
*
DALISAY JIMMUEL M.
The Philippines, a large archepelago consisting of 7,600 island. Mostly lined
by coral reefs, seagrass meadows, and mangrove forests, and surrounded by
waters with variable currents driven by a reversing monsoon system.
With the occurance of Climate change due to Global Warming,Philippines
become highly vulnerable to the impacts of climate change, including sea level rise,
increased frequency of extreme weather events, rising temperatures and extreme
rainfall.
This is due to its high exposure to natural hazards (cyclones, landslides,
floods, droughts), dependence on climate-sensitive natural resources and vast
coastlines where all major cities and the majority of the population reside.
(https://www.climatelinks.org/resources/climate-risk-profile-philippines)
Sea erosion is currently affecting many coastal areas in the Philippines. Natural
factors such as wind and waves are to blame, as are human activities such as
coral reef destruction. The scale and impact of this problem are both expected to
become more widespread due to climate change and sea level rise.
On 2016 in the Province
of Leyte
Uprooted coconut trees
and diminishing shore were
observed in Brgy.
Hipusngo, Baybayin City,
Leyte. These are evidences
of high susceptibility to
coastal erosion.
Landslide along the
limestone hills of Brgy.
Libagong, Villaba, Leyte. The
colluvium of trees and soil
indicates the recent mass
movement in the area.
Coastal erosion in
Panay, central
Philippines, showing (a)
damage to coconut
plantations in Ibajay,
Aklan, and to rural
houses with only
concrete structures
(e.g., toilet fixtures)
remaining in (b)
Tigbauan, Iloilo and (c,
d) Leganes, Iloilo.
Photos by J.H.
Primavera.
*
Executive Order No. 533, adopting Integrated Coastal Management (ICM)
as a national strategy to ensure the sustainable development of the country’s
coastal and marine environment and resources and establishing supporting
mechanisms for its implementation, was signed by former President Gloria
Macapagal-Arroyo on June 6 2006.
The ICM and related approaches, such as coastal resources and
management or coastal zone management, shall be the national management
policy framework to promote the sustainable development of the country’s coastal
marine and environment and resources to achieve food security, sustainable
livelihood, poverty alleviation, and reduction of vulnerability to natural hazards while
preserving ecological integrity ( Section 1).
The ICM covers all coastal and marine areas, addressing the inter-linkages
among associated watershed, estuaries and wetlands, and coastal seas by all
relevant national and local agencies (Section 2)
*
The Department of Environment and Natural Resources (DENR), in
consultation with other concerned, sector and stakeholders, has been tasked to
develop a National ICM Programme to provide direction, support, and guidance to the
Local Government Units (LGU) and stakeholders in the development and
implementation of their local ICM programs.
The National ICM Programme shall include principles, strategies, and action
plans identified after balancing national development priorities with local concerns,
define national ICM targets, and develop a national ICM coordinating mechanism
(Section 3).
*
The implementation of ICM programs shall take into account the following elements:
a. an interagency, multi-sectoral mechanism to coordinate the efforts of different
agencies, sectors, and administrative levels;
b. coastal strategies and action plans that provide a long term vision and strategy for
sustainable development of the coastal area, and fixed-term program of actions for
addressing priority issues and concern;
c. public awareness programs to increase the level of understanding of, and
appreciation for, the coastal and marine resources of the area, and to promote a
shared responsibility among stakeholders in the planning and implementation of
ICM program;
d. mainstreaming ICM program into the national and local government's planning
and socio-economic development program and allocating adequate financial
and human resources for implementation;
e. capacity building programs to enhance required human resource skills,
scientific inputs to policy and planning processes, and enforcement
mechanisms to ensure compliance with adopted rules and regulations;
f. integrated environmental monitoring to measure the status, progress, and
impacts of management programs against sustainable development indicators,
as may be established, and for use decision-making, public awareness, and
performance evaluation
g. investment opportunities and sustainable financing mechanism for
environmental protection and improvement and resource conservation
PRESIDENTIAL DECREE NO. 1067
December 31, 1976
THE WATER CODE OF THE PHILIPPINES
A DECREE INSTITUTING A WATER CODE, THEREBY REVISING AND
CONSOLIDATING THE LAWS GOVERNING THE OWNERSHIP,
APPROPRIATION, UTILIZATION, EXPLOITATION, DEVELOPMENT,
CONSERVATION AND PROTECTION OF WATER RESOURCES.
CHAPTER V
CONTROL OF WATERS
* Art. 53. To promote the best interest and the coordinated protection of flood plain lands,
the Secretary of Public Works, Transportation and Communications may declare flood
control areas and promulgate guidelines for governing flood plain management plans in
these areas.
* Art. 54. In declare flood control areas, rules and regulations may be promulgate to prohibit
or control activities that may damage or cause deterioration of lakes and dikes, obstruct
the flow of water, change the natural flow of the river, increase flood losses or aggravate
flood problems.
* Art. 55. The government may construction necessary flood control structures in declared
flood control areas, and for this purpose it shall have a legal easement as wide as may be
needed along and adjacent to the river bank and outside the bed or channel of the river.
*
DPWH completes P96.5-M
river-control project in
Batangas City
Thursday, February 27, 2020
A newly-completed 360-meter
retaining wall now protects
residents along Calumpang
River in Barangay Gulod
Labac and Barangay Pallocan
West, Batangas City.
https://www.dpwh.gov.ph/DPWH/news/18635
DPWH completes P24-million flood
control project in Pangasinan
Monday, March 11, 2019
Citing a report from Pangasinan 4th District
Engineer Simplicio D. Gonzales, Secretary
Mark A. Villar said that the flood control
project was implemented with a total budget
cost of P24.57 million which involves the
construction of a 550-linear meter gabion
revetment wall and rubble concrete along
the Ingalera River.
DPWH-installed gabions will help in
preventing erosion along the riverbank as
well as reducing the abrupt rising of water in
the area.
https://www.dpwh.gov.ph/dpwh/news/15066
DPWH-NCR completes the construction of 152-linear meter river wall in the right
bank of Marikina River in Barangay Batasan Hills, QC in time for the rainy season.
(Photo courtesy of DPWH)
P122-M flood control project
in Isabela town completed
The Department of Public Works
and Highways-3rd Isabela District
Engineering Office (DPWH-3rd
DEO) has completed the P122
million Magat River flood control
project in San Mateo, Isabela.
The flood control structure started
its construction in June 2019 and
completed in December 2019 with a
length of 840-lineal meter rubble
concrete and revetment on steel
sheet piles
*NATURAL MATERIALS
USED IN RIVERBANK
PROTECTION
*
• Consists of woven fibers of coconut
husk.
• The fabric is available in rolls that
can be rolled out over the surface of
an embankment, preventing soil
erosion on newly graded slopes.
• Unlike non-woven geotextile fabric
made from synthetic polypropylene or
other materials, coir geotextile is a
biodegradable material that will not
harm the environment.
• This method is usually used on the
banks of small streams that have a
consistent surface water level.
• Sometimes vegetation can be established over the
geotextile, so that the roots of the vegetation
growing up through the fabric interlock with the
fibers.
• Don’t use geotextile fabric along channels that
transport large quantities of sediments.
The advantages of geotextile:
• Simplicity of installation
• A fully biodegradable product
• Relatively low maintenance
*
• Also known as live brush mat,
is a means protecting stream
banks by combining live brush
cuttings, facines (bundles of
sticks or other materials) and
stakes to cover and stabilize
stream banks.
• Its construction involves
placing a thick mat of
dormant brush cuttings on the
bank and anchoring them with
stakes. The cuttings
eventually root into soil and
stabilize the bank
• The technique is often used
with other methods.
• This method is ideal for capturing
sediment carried down banks by rain.
The drawback is that the facine
bundles can be washed away if the
rains are very heavy.
Advantages of this technique:
• Ideal for use along streams that
receive plenty of sunlight, which
will help the cuttings quickly
root
• Quick installation
• Fully biodegradable system
• Low maintenance
• A rootwall composite
system consists of a
combination of interlocking
tree materials and other
vegetation.
• A mass of tree roots,
known as a rootwad, is
combined with other
vegetative materials, and
is often combined with
other techniques to
* stabilize stream banks. The
rootwad is placed within
the stream bed or at the
base of the slope to direct
the stream flow away from
the bank, thus reducing
erosion.
• In addition to
stabilizing the stream
bank by lowering the
water-flow velocity,
the roots provide
complex habitats for
the establishment of
aquatic wildlife.
Advantages of a rootwad • Although this is an
composite system includes: inexpensive system,
the installation is
• Inexpensive to install highly complex, which
• Eventually decomposes puts some limitations
completely on its use.
• Provides habitat for marine life
*
• The word gabion comes
from an Italian word
meaning "big box."
• Gabions combine the use of
natural stone with
manufactured metal wires.
The system consists of
pouches, baskets, or boxes
made of high-strength,
double-twisted hexagonal
mesh filled with stone (or
sometimes concrete rubble).
• Used for bank stabilization
in areas where high soil
erosion is likely to occur.
• Gabion's mattresses or boxes are not
particularly attractive, and there is
always the possibility of damage to the
mesh.
• Can be used almost everywhere, but
special conditions and precautions must
be taken on areas susceptible to rapid
erosion and unstable water flow.
Advantages to Gabions:
• Can be installed underwater to "train"
streams to a desired path
• Very strong system that resists heavy
water flow
• Porous construction slows the
velocity of water flow
• Invisible when submerged along a
stream bank
MODERN COASTAL
PROTECTION
METHOD
* Modern design practice places much emphasis on attempting to
hold a healthy beach on the shoreline as the primary means of
protection.
* These so-called ‘soft’ solutions are generally considered to be
more environmentally friendly than traditional ‘hard’ protection
works. However, where human life may be at risk and high
density, high value conurbations exist, the use of hard elements
of a defence may be unavoidable.
*
Beach replenishment/nourishment involves importing sand from
elsewhere and adding it to the existing beach. The imported sand
should be of a similar quality to the existing beach material so it
can meld with the natural local processes and without adverse
effects. Beach nourishment can be used in combination with
groynes. The scheme requires repeated applications on an annual
or multi-year cycle.
Stabilising dunes can help protect beaches by catching windblown sand, increasing
natural beach formation. Dune stabilisation/sand dune management employs public
amenities such as car parks, footpaths, Dutch Ladders and boardwalks to reduce
erosion and the removal of sand by humans. Noticeboards, leaflets and beach
wardens explain to visitors how to avoid damaging the area. Beach areas can be
closed to the public to reduce damage. Fences can allow sand traps to create
blowouts and increase windblown sand capture. Plants such as Ammophila (Marram
grass) can bind the sediment.
*
RIVER BANK PROTECTION
BY: MA.ELIZABETH B. MACATANGAY
*
Riverbank restoration are management tools put in place
to protect, enhance and restore riverbanks. As our climate
changes, wetter and more extreme weather patterns are
causing serious damage to riverbanks and aggravating
already sensitive areas & the streambank restoration is
one practice that helps restore the healthy equilibrium of a
stream corridor. And here’s the video that illustrates both
structural and soil bioengineering methods of streambank
restoration that can be employed to control excessive
erosion.
https://www.youtube.com/watch?v=YX72P67YnhE
*
*Brick Pitching
*Stone Riprap
*Boulder Pitching
*Concrete Slab Lining
*
first of all, around 3m length of bamboo or timber piles are
driven along a line about 1 m away from the toe of the river
embankment, and the center to center distance between
one pile and the next pile is kept 15 cm.
The layer of brick flat soling is provided on the space
between the toe and the pile line. Then usually, 15 cm
thickness of cement concrete (1:3:6) is laid over the brick
flat soling on the room between the toe of the embankment
and the pile line.
The sloping side of the bank is protected by double-layer
brick pitching with cement mortar of 1:6 ratio.
*
In this method of bank protection, Around 3 m length of timber
piles are driven at 1 m center to center along the line about 1
m away from the toe of the embankment. The piles are
projected about 45 cm above the ground surface.
Then the boulders enclosed in wire net is provided along the
space between the toe and the pile line. And for the protection
of the sloping side of the embankment, stone riprap finished
with cement mortar is provided.
*
In this method of river bank protection, around 4 m to 5 m length of timber
piles are driven at 1 m center to center, along the line about 1 m away from
the toe of the embankment. The piles are projected about 50 cm above the
ground surface.
Then, within the space between the toe and the pile line, two layers of
boulder apron are provided. The sloping side is lined with boulder pitching
which is finished with cement mortar.
*
In this method of bank protection, A wall is constructed along
the bank of the river. This type of wall is called the toe wall.
Then the concrete slabs are placed on the space between the
toe of the embankment and toe wall, and it is set by using
cement mortar. The sloping side of the embankment is lined
with concrete slabs, and joints are finished with cement
mortar.
Depending on the site condition, concrete slabs may be of
different sizes. Usually, the size of the concrete slab (50 cm X
50 cm X 10 cm) is used.
Flood
*Causes of river bank erosion:
* Flood is the most crucial reason of river bank erosion. The chances of flood
increases in the rainy season. During flood the huge amount of water flow
with higher velocity brings enough energy to tear away the top layers of soil or
even causes mass failure. The water elevation is raised by centrifugal force
resulting highest depth of flow at outside bend and gravitational force pulls
down the water. This downward velocity against the bank is the erosive force.
Heavy rainfall
* Soil can be eroded by heavy and excessive rainfall. Heavy rainfall often causes
strong waves which can loosen and wear away non cohesive bed materials.
Sedimentation
* Various disturbances in the nature can cause sedimentation. Silt accumulation
at the river beneath reduces water holding capacity of a river as saturation of
banks occurs. So the direction of river is changed. Thus meandering rivers are
formed eroding river bank.
* https://www.youtube.com/watch?v=EMwGPPJ1Umk
*
A major key to protecting your river property is to maintain, stabilize, and repair your
riverbank. This river edge is the bulwark that stands in the soil and prevents your
property from washing away. It is an essential part of the whole river ecosystem. The
TrapBag® barrier system can be applied to stabilize the riverbank for temporary, semi-
permanent or even permanent purposes when filled with concrete.
Bank degradation leads to property damage or loss, sedimentation of in-stream
structures, water quality deterioration, aquatic habitat damage, channel widening, and
more.
Riverbank stabilization is intended to protect river and stream banks from deterioration
due to erosion and prevent lateral migration of the alluvial channel when there is
property at risk.
https://www.youtube.com/watch?v=Tv30Wln7ZEU&t=7s
THANK YOU FOR LISTENING!
Godbless!
