environmental aspects of coastal cities

8/19/2019 Environmental Aspects of Coastal Cities

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SIX FEET UNDER (water)the Environmental Aspects of Coastal Cities

DEVIKA HEMALATHA DEV I pp0002513


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CITIES AND COASTAL ZONES

Since ancient times, it has been recognized that the coast -a confluence of the atmosphere, lithosphere and hydrosphere -yields diverse livelihood opportunities. In fact, the very reason forthe resilience and endurance of coastal cities has been this con-

fluence. Aanalysis of ancient megacities indicates that cities thathave witnessed decline have irrefutably been non-coastal cities.Cairo, Istanbul (Constantinople) and Baghdad began the secondmillennium as they ended it - among the world's largest cities.However, cities are not only thresholds for economic change, theyare also highly concentrated consumers, distributed on the world'sglobe. And, without proper governance and management policies inplace, they can rapidly turn into parasites - draining surroundingregions for indigenous benefit.

Coastal zones are dynamic and not always the same size, ex-tending a few hundred meters wide in some areas, while con-taining interconnected physical and ecological features in others.(Vaz and Bowman, ). These may include watersheds, drainagepassages, floodplains, mangroves, swamps, estuaries, salt marsh-es, beaches, dunes, wetlands, barrier islands, coral reefs and tidalflats. Invariably, they provide valuable ecological services and havebeen manipulated for economic activities - including clean water,food and waste disposal. By all commonly used measures, thehuman wellbeing of coastal populations is much higher than thoseof inland communities.

However these areas also witness the highest population densities- coastal population densities are 2.6 times higher than inlandpopulation densities - with nearly half the world's major cities lo-cated within 50 kms from the coast. It derives naturally that oftenthe poorest people in cities are found in unauthorized shantytownareas (UN/ISDR 2002b), including Bombay, Lima, Calcutta, Manila,Karachi, Jakarta, and Rio de Janeiro (Devine 1992). Built in theleast desirable areas, these are the least secure portions of thecity - beyond the scope of management strategy. For example, inRecife, Brazil the favelas are expanding in mangrove areas, whichare by definition at or below normal high water (Muehe and Neves1995). More to the point, high concentrations of urban poor oc-curs along the coasts of developing countries already grapplingwith economic issues. The prognosis for such cities in the faceof a natural disaster is alarming, at the least.


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Coastal ecosystems perform three major functions -

1. Provisioning - providing primary goods for consumption, in-cluding food, water and oxygen (be acting as acrbon sinks)2. Regulating - mainaining natural processes ssuch as climate

regulation, hydrologic flows and cycles and removal of excesswastes3. Aeshetic - providing aesthetic and educational value, comfort

and religious and culturaal significance.

In over-using any ecosystem, we run the risk of damage toecosystem balance and an irretrievable breakdown of its life-cycleand useful functions. Once a critical threshold is passed, all ittakes is a small trigger event to push the entire system over edge.

The over-use of an ecosystem may occur through various directand indirect factors. While the irect factors (or proximate factors)are active prccesses that are responsible for over-use, the indirectfactors are the underlying root causes behind the continutaio ofthese processes over a long period. These passive processes in-clude population expansion. economic and social inequalities (thatdrive the poor emphasize survival over sustainability), policy fail-ure, maket failures (that underprice natural resources) and poordevelopment models (that confusedly equate increased consump-

tion with increased growth).


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COASTAL EROSION

Coastal erosion is one of the most visible problems affectingcoastal regions around the world. It refers to the gradual wearingaway of the coastal edge. accelerated by anthropogenic activity.

A study on coastal erosion processes along the Golden Horseshoeregion in Canada found that there were increased trends of castalerosion in rangelands and agricultural lands, i.e, vacant landssurrnding urban development. The same phenomenon was alsoseen in areas along the New Orleans coast where pile-supportedbox culverts remain high while the adjacent land falls away.Increased coastal erosion can reduce beach areas and protec-

tive barrier islands, creating a phenomenon of coasta lsqueeze,where cities are locked between the sea and higher terrain. It may

also interfere with nearshore currents and their physical transportpatterns. Subsequent changes in drainage and irrigation patternsand modifications of fluvial flows can reroute sediment transportnutrient runoff into coastal waters.


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COASTAL SUBSIDENCE

Several coasts show tendencies of subsidence, i.e, the gradualsinking of land below the mean sea level. This is particularly trueof dellta regions immediately after dam constructions (eg: the

Aswan dam was partly responsible for the subsidence of the NileDelta). In areas of increased groundwater extraction (such as inhighly dense urban areas and urban farming regions) this natu-ral subsidence rate has been accelerated. Excessive groundwaterextraction leads to compaction of water aquifiers which may laterbecome unreplenishable.In the South Gujarat region, for example, the perceived availabil-

ity of water (through the Narmada irrigation project), has causedfarmers to completely convert to intensive cropping practices such

as cotton and sugarcane cultivation. These areas, earlier knownfor oiseed production, have onverted to highly water intensive cashcrops in the course of a decade. Farmers have laid pipelines fortens of kilometres in order to connect to subsidiary pipelines ofthe irrigation project. However, the availability f uch water re-mains suspect. In the meanwhile, these farmers increasingly relyon groundwater for their irrigation needs, exarcebating saline in-trusion, groundwater decline and rapid subsidence.

In a number of Asiancities, the magnitude ofland subsidence is greaterthan global or regional sealevel rise. In Bangkok, theGulf of Thailand is risingabout 0.25 cm per year,but the city is sinking ata far faster rate, up to 4

cm per year. In north Ja-karta, subsidence has beenmeasured at 6 cm peryear, and sinking bridgeshave now become obstruc-tions to water discharge.As cumulative subsidenceof these regions increase,poorer poulations are proneto increaed flooding andassociated disease.

KINGSTON ON HULL


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DISASTER VULNERABILITY

The dense coastal zones of the world are highly prone to theravages of the sea and wind. It follows that developing cun-tries are more backward in dealing with such disasters, in terms

ofmitigation and adaptation. As land use changes and demand forland increases, newer developments are pushed to the outskirts,which, in coastal cities incvolve more hazardous ground.The 2011 Tohoku earthquake, a 9.0 megathrust undersea earth-

quake off the coast of Japan caused destructive tsunami waveswith heights of up to 38.9 meters (128 ft). Traveling as far as10 km inland in some places, it caused immense loss of lifeand destruction of infrastructure; but perhaps its most devastat-ing impact was the destruction of the Fukushima I Nuclear Power

Plant, which led to evacuation in a ring of 20 km around theevent. The overall cost could exceed $300 billion, making it themost expensive natural disaster on record.

In 1913, highly effifficient screw pumps were invented by Albert Baldwin-Wood and installed at outfall canals draining backswamps to the lake. Withthe deployment of these powerful pumps, the New Orleans drainage systemwas the most technologically advanced system in the world. With confidencein this mastered terrain, post-World War II development near the lakeshoreabandoned the traditional raised housing type slab-on-grade houses domi-nated the new landscape. Ironically, the newly available land was below sealevel and continually subsiding due to the same drainage system of levees

and pumps that permitted its development.


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waste disposal and associated pollution

One over-riding characteristic of urban centres is that their sup-port base is now global, with sophisticated supply lines, but theirwaste disposal is almost entirely local. In the absence of proper

wstemanagement strategy and treatment mehanisms, direct wasteflows into rivers and oceans leading to algal bloom and the cre-ation of hypoxic water. These water (also known as dead zones)are devoid of fish and take several decades of recovery to becomeeconomically viable. Contained shrimp farming has expanded rap-idly in the past several decades. Destruction of coastal habitats,especially mangrove forests, has been attributed in particular toextensive shrimp farming. Caught in the midst of this, it is the lo-cal fisherman that suffers. Not only is his livelihood opportuity lostto him, he is subject to the toxic effects of such pollutants and

the hazardous environment they create. In Mauritiana, only 10%of the local catch was available to fishermen while the remainingwent to commercial operators, the highest share belonging t theNetherlands.In addition to threats from waste disposal, indigenous fishing

communities are also prone to the hazards that arise by com-mercial overfishing (through bottom trawling) and the introdctionof invasive species (through port operations). For many coastalpopulations, largescale, industrial bottom trawling of their tradionalfishing grounds (often carried out unregulated illegally and unre-ported by distant fishing fleets) ruins local fisheries with devastat-ing effects on local fishermen, industry and livelihoods. Even moredistressing is the discarded bycatch that could sustain small scaleoperations. Over one-third of the World catch is simply discardeddue to inappropriate fish sizes, or simply due to unintended by-catch, particularly as a result of bottom trawling. In the Black Sea,overfishing and eutrophication triggered a trophic cascade leadingto a massive bloom of the invasive comb jelly, that went on todecimate local fish populations.(Daskalov et al. 2007).

In about five years, 60% of the population in Jamaica will residein urban areas, such as Montego Bay, and a third will be located ininformal settlements not served by adequate household waste dis-posal. Only 25% of the country's households are connected to sewersystems, and even where such connections exist, wastewater treat-ment is inadequate. In addition to the dangers of pollution, it re-sults in a loss of aesthetic value to several communities, especiallythose dependent on tourism as their major souurce of income (eg.island nations such as the Phillipines and others, located along thePacific Ring of Fire)


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MANAGEMENT STRATEGIES

In addition to conventional management strategies, involving citylevel initiatives for clean water, waste management and reducedcarbon emissions (associated with increasing climate change), there

are initiatives to be taken along the shoreline at a regional scale.The present delineation of the coastal development edge is highlyarbitrary, and priarily dictated by monetary considerations. It isto be recognized that dyamic coasts must be dealt with steadilychangig and updated strategies for development. In island citiessuch as the Phillipines and the UK, innovative strategies are calledfor in the face of restricted land for development. Based on this,three strategies have been looked at for future coastal manage-ment:

1. Retreat Schemes:It is to move critical infrastructure and housing to safer ground

and to allow the water into the city to alleviate flood risk. Man-aged Retreat, or Managed Realignment is a method of removing orbreaching coastal defences, allowing tidal seawater to flood areaspreviously protected. The line of defence is then relocated land-wards. It could help in the regeneration of salt flats and intertidallagoons and marshes, that could serve as natural protection againstdisasters.

2. Defensive Schemes:To defend is to ensure the sea water does not enter the existing

built environment. This si presently followed in several countries,including the Netherlands and Venice. It requires built defences toensure the standard of protection will be met in the distant futureas sea-levels rise.

3. Advancing Schemes:This scheme involves stepping seaward, ahead of the existing

coastline. Suitable for island cities, with limited land to develop , itreduces the need to sprawl into the countryside and ensures theirsustained social and economic vitality. Floating structures, fromboats to pontoons, have been used for housing and civil infra-structure.

Follwing is a series of diagrams, that indicate how these schemeswould be implemented along the coast of Kingston on the Hull,England, in the face of rising sea levels.


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KINGSTON ON HULL

The Hull is a relatively flat city which ranges from2-4 metres above sea-level. Some areas of Hull al-ready lie on reclaimed land at, or below, sea-level.In 2007, Hull was severely affected by the summer

floods due to substantial rain. Coupled with run offfrom surrounding high ground and the flat topogra-phy of the city, it rsulted in standing water, affecting20% of the city's housing and costing an estimated£100 million in damages to schools alone. It is es-timated that over 8000 houses and 100 businesseswere flood damaged. None of Hull's flood defenceswere breached or failed, but the city's drainage in-frastructure was unable to cope.

RETREAT SCHEME

DEFENSIVE SCHEME

ADVANCE SCHEME


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environmental aspects of coastal cities

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