ISLT '98 International Symposium on Lowland Technology

Organized by The Institute of Lowland Technology, Saga University

Saga, 4-6 November 1998


A cursory review of the location of cities would show that an overwhelming majority of human settlements have been, and continue to be, located in lowland areas. River deltas, seashores and other lowland areas have been favoured sites for cities since the early days of the "urban revolution".

The reasons for this predilection for lowland sites are quite obvious. At the dawn of history settlements were associated with agriculture, an activity requiring plentiful water and fertile soils, elements found in river deltas and other lowland areas. Thus, early civilizations (a term that shares its root with cities) developed in Mesopotamia, the Nile delta, and along the Indus and Yellow Rivers. Cities flourished in these environments. An illustration of the beneficent dependency of cities on lowland conditions is the observation of the Greek historian Herodotus - who upon visiting Egypt over 2,400 years ago - was so impressed by the contribution of the Nile to the development of Egyptian civilization that he declared the country to be "the gift of the Nile."(1) The same can be said of most other early civilizations, their development was nourished by the affluence prevalent in lowlands. As a consequence human settlements were located in such areas.

In the intervening millennia this pattern has been repeated throughout the world. In fact, even in some areas which are not readily identified as being lowlands, such as the valley of Mexico, we find that the environmental conditions that supported the initial development of cities and sustained high civilization were in fact quite similar to those associated fluvial plains. The valley of Mexico is in reality a basin which, until recent centuries, contained a complex system of shallow lakes. In essence a lowland area located over 2,200 metres above sea level. Although located high in the mountains and far from the seashore, the basin had many of the characteristics associated with lowlands.

As trade and commerce gained in importance the banks of rivers and seashore sites remained favoured locations for the development and growth of human settlements since water transport was the most efficient way to move goods from one place to another. Ideal locations for cities were river deltas, points where major rivers meet the oceans. Here rivers which drained large agricultural areas also provided the natural road to transport the products of the region; bringing the goods to the seashore where they could be transshipped to foreign lands. Most of the great cities of the last few centuries have indeed been located in such areas. Examples abound from New York to Shanghai. Even in Japan we find that although there are no great rivers the fluvial plains and deltas have been favoured sites for urbanization, both for their agricultural productivity and favourable transport characteristics.

With the advent of the industrial revolution and advances in land and air transport experienced this century, the comparative advantages of lowland locations have diminished to some degree, and major cities have developed under many different geographic conditions. But the history long heritage of urbanization in lowland areas remains and still dominates the pattern of distribution of population on the planet.

In recent decades the process of rapid urbanization, which started after the Second World War, has resulted in a large increase of population in settlements in lowland areas. This process, which was initiated in part by decolonization and which has accelerated in the past quarter century, due to many factors including industrialization, is mostly due to natural population growth and limitations in rural areas to absorb high rates of population increase. According to the United Nations estimates, the world's urban population will surpass the 60 percent mark by the year 2005, of which, according to some researchers, approximately one half will be living within a 60 km from seashores.(2) Most of the inhabited areas in this belt will be lowlands.

With population growth expected to continue for several decades before levelling off sometime after the middle of the next century, we can expect cities in lowland areas to continue growing in terms of absolute population and density. Thus, the challenge is clear, both in percentual and absolute terms more of humanity will be living in lowland areas in the decades to come. Since settlement development in lowland areas presents certain challenges in terms of the impact on the environment and risk associated with natural phenomenon special attention must be paid to these factors.


The primary consideration in terms of the development of human settlements in lowland areas is the competition for land with agricultural activities. Lowlands generally contain some of the most fertile soils and are highly productive in terms of agriculture; yet, under prevalent market forces, agricultural uses become subservient to urban development. The value of land close to cities tends to favour urban uses over agricultural ones. This is an economic issue that can only be resolved through the adoption of appropriate land use policies.

Beyond the issue of competing land uses, there are many challenges that must be addressed in terms of human settlement development in lowland areas. For all the historical locational advantages of lowlands, such sites also present major developmental challenges as far as human settlements are concerned. The very presence of water, essential to the sustenance of life in settlements, requires control. The soil types associated with alluvial deposits also make special demands on construction and urban development. The proximity to the sea of most lowland areas also poses dangers to the population living in low-lying areas. The challenges posed by the habitation of lowlands have been greatly exacerbated in modern times, primarily as a function of increased population numbers and densities, and also as the result of cities becoming increasingly more technologically complex. Some of these challenges are discussed in the following pages.

Environmental impact of development on lowland areas

The environmental impact of development on lowlands is perhaps the most crucial of these challenges. In particular is the negative impact on water resources, the very element that favours development in lowland areas in the first place. The more generalized problem in this regard is the pollution of water sources and contamination of coastlines caused by the growing concentrations of population. The increase of population leads, in many cases, to cities having to tap subsurface sources of water to augment strained or polluted surface sources. The extraction of subsurface water precipitates ground subsidence, which, in turn, exacerbates other problems characteristic of lowlands, such as flooding. In locations along sea shores the drawing of subsurface water may also induce the intrusion of salt water into the aquifers supplying the urban area. A process that not only spoils the water supply, but which takes a very long time to reverse, thus the damage is, for all practical purposes, irreversible.

Moreover, lowland areas often contain rich and varied ecosystems, that is the reason many of them were settled in the first place, and that large settlements were able to develop in such locations, but the process of urbanization is most destructive to these ecosystems, particularly through contamination of the water systems. Not only are land ecosystems affected, but in the case of coastal locations, so are the marine ecosystems in the adjacent sea. The land and marine ecosystems are often highly integrated and interdependent in deltas. Disruption of an ecosystem in either macro-environment can, and often does, have consequences on other ecosystems, in both land and water.

To remedy the problems engendered by development, cities in lowland areas often undertake expensive, large projects to treat wastewater and build aqueducts to bring fresh water from yet more distant sources. All the while, affecting the environment far from their location as they deprive those areas from their own water. Thus, the impact of development in lowlands may be felt in distant highland areas.

Vulnerability to natural disasters

Another set of important challenges to development in lowland areas is the vulnerability of these areas to a variety of natural hazards. Principal amongst these hazards is the natural propensity of these areas to floods. This is specially critical in deltas still under formation such as the Ganges River delta in Bangladesh. In such cases land is still under formation, floods easily eradicate some land areas and form others in a matter of days during flood periods. In the process all human habitation is severely disrupted. More stable deltas and other lowland areas are subjected to flooding due to poor drainage conditions. Cities such as Manila, in the Philippines, are regularly subject to flooding in the rainy season due to this factor. In vast areas of the Province of Buenos Aires, Argentina flood water remains for weeks and months at a time for this same reason. Human settlements located in such areas must invest in major public works to ensure protection from floods, and such protection is never fully achieved.

The hazardous conditions prevailing in lowlands can, and often are, exacerbated by human intervention. As mentioned earlier, as human settlements grow their demands for water lead to greater and greater withdrawal of groundwater, this in turn leads to ground subsidence and aggravating those hazards inherent in lowland topography. One example of this is the city of Bangkok which is located on a plain some 48 km from the sea at a mean elevation of 1 to 1.5 metres above sea level.(3) Here a number of factors can produce flooding conditions, these include high discharge in the Chao Phraya River, high tides at the mouth of the river, and heavy rainfall in the plain. When several of these factors occur simultaneously flooding can be most disastrous. Contributing to the high degree of vulnerability to floods already naturally occurring in Bangkok is a fourth human induced factor: ground subsidence due to ground water withdrawal for consumption by the city itself. Many other cities are experiencing difficulties because of this man-made factor, most notable among these cities are Venice, Shanghai and Taipei.

Seismicity is another natural hazard with some particular implications to lowland areas. The geomorphological aspects of lowland areas are often quite complex. Most lowland areas have been formed from alluvial deposits which have been deposited through the ages in a constant interplay of various factors. The resulting subsoil structures are complex with particular and location specific responses to seismic events. Consequently an earthquake may result on very different degrees of damage being exhibited over an urban area. For this reason micro-zoning studies are of great importance for the development of human settlements in lowland areas. Moreover, building codes and regulations for cities in such locations should reflect the variations on seismic response from one part of the urbanized area to another. This is seldom done, but for example the building codes for Mexico City do reflect the differences in geomorphology by having different codes for three major types of subsoil conditions.

A particular phenomenon associated with seismic events in lowland areas is liquefaction.(4) The damage within areas subjected to liquefaction is generally very generalized, that is most or even all structures are affected. In the Luzon earthquake of 1990 many coastal settlements were affected by liquefaction, and the damage in these areas was considerable.(5) Liquefaction is a phenomenon occurring where there are sandy deposits in the subsoil. Therefore mapping of sandy deposits that may react in such manner to an earthquake is of great importance in urbanized areas. These deposits are generally identified in micro-zoning studies, but even where there are no such studies areas subject to potential liquefaction should be identified and building codes made to ensure adequate response of structures to earthquakes.

Another phenomenon associated with seismic activity and of particular threat to coastal settlements are tsunamis. A characteristic of many coastal lowland areas is that they are alluvial plains, triangular in shape and flanked on two sides by hills or mountains. These morphology amplifies the effect of the incoming wave as it travels inland. In countries such as Japan protection from tsunamis through the building of seawalls and other protective structures is practised to a degree. However, in poor countries such expensive public works projects for protection from events that are neither regular in occurrence or predictable are given low priority. Yet, we recently witnessed the enormous destruction of a tsunami in the rather uninhabited coast of northern Papua New Guinea. A similar tsunami hitting the port of Callao in Peru would sweep the entire city and even affect Lima. Callao, extending into the sea can not easily be protected from sea level surges; yet, it is a major centre of economic activity for the whole country.

Since many lowland areas are found either along seashores or close to the sea, these areas are also particularly vulnerable to typhoons and similar types of storms which originate in open water. Such storms bring not only heavy precipitation and strong winds, but often are accompanied by surges in the tides. The regularity and frequency of such storms appears to be showing some signs of increase due to climatic changes. And certainly with settlements in lowlands growing more population will be at risk.

Exposure to global warming

Beyond the special considerations that arise from geographical and geotechnical conditions and vulnerability to natural disasters, lowlands are particularly at risk from the consequences that could accrue from global warming. The general consensus among scientists is that there is, in fact, a general trend towards global warming, and that global warming will lead to sea level rise. Such a phenomenon would affect developed and developing nations alike.

The report of the Intergovernmental Panel on Climate Change (IPCC) meeting held in 1992 provided a global overview of the risks to low-lying coastal areas from sea level rise based on 25 case studies. One of these studies, carried out by Delft Hydraulics Laboratory (1990) on 181 coastal countries and territories estimated that 345,335 km of lowland coast, including 6,400 km of urban waterfronts, 10,725 km of sandy beaches, and 1,756 km of harbor areas would have to be protected in the case of sea level rise of one metre.(6) The study, provided a list of 50 low-lying coastal areas, which included the most vulnerable small island states, ranked on the basis of the estimated annual cost of protection of their shores as a percentage of their respective GNP.

Reliable data on size and density of coastal populations, even at global level, is difficult to find. In 1990, the United Nations Centre for Human Settlements (Habitat), conducted a preliminary study of population living in coastal areas, based on the United Nations world and urban population data for 1980 and projections for the year 2000.(7) According to this study, in 1980, about 35 percent of the total global urban population lived in coastal areas (defined as a 60 km wide zone from the water line), on 8.3 percent of the world's land surface. While the percentage of global coastal urban population is expected to remain the same for the year 2000, the absolute number of people living in lowland areas will be far greater. The estimates, seem to be on the low side due to a number of limitations including the lack of precise statistical data, definitional problems as to "urban agglomerations", and exclusion of rural/agrarian coastal villages. Other figures suggested by IPCC and other sources are much higher.

Information on the size and distribution of coastal populations and settlements is one of the basic requirements for the formulation of response strategies. Edwards (1989) writes that: "Estimates of the future sizes of coastal populations are germane to coastal management because many indicators of resource use, such as participation in marine recreational fishing, total consumption of seafood, beach attendance, residential development, wetland destruction, marine pollution, shellfish bed closures, and traffic can be traced to population size and its distribution relative to the coast." (8)

The problem with the lack of availability and reliability of data at the global level is a reflection of the same problem at the country level. Estimates on the percentage of urban and global population living in coastal areas, at present, range anywhere between 1.6 to 2.8 billion people live in coastal areas. The process of urbanization for developing countries is not yet completed, and as a result of further urbanization of the developing world, the population pressure on low-lying coastal areas will increase within the next two decades.

Some researchers have addressed the issues of population growth, urbanization, formation of informal settlements in coastal zone and their relationship with climate change and sea level rise. One of the writers who has addressed the issue of the effect of climate change on population is Nathan Keyfitz. He, for example, believes that responding to rapid climatic changes will be less difficult for a population which grows slower than the one which grows at a faster rate.(9) To prove his point, he gives the example of Bangladesh, saying that Bangladesh in 1950, with 42 million population would have had less difficulty relocating part of its population as a result of an inundation caused by a 1-metre sea level rise, than it will have in the year 2020, relocating the same fraction of an expected population of 206 million.

Keyfitz also recognizes the interdependence of population growth, mobility of the population, technological change and adaptability of countries to climatic change and sea level rise. In his analysis, countries with lower population growth, higher mobility and higher capacity for technological change are in a better position to adapt to new conditions, and as a result they are less vulnerable to the negative impacts of climate change and sea level rise. (10)

But the impact of sea level rise in economic terms would be greater in developed countries. For example, a risk analysis of flood dangers for the city of Hamburg, "established that more than 200 square km of land could be flooded, 180,000 inhabitants and 140,000 employees in the city endangered by the rising storm-tide water levels. if the rise in tidal water levels occurred as predicted and feared today. The potential damage caused by flooding amounts to approximately DM 16 billion, and 60, 000 homes and 8, 000 industrial plants would be in danger.(11)

In Japan, many settlements would be at risk if the sea level does rise due to global warming. Not only would large numbers of the population be at risk, but the impact on the economy would be very significant. One dramatic example is Osaka with a population of over 2.5 million and annual industrial production of approximately US$500 billion. This city is highly vulnerable to sea level rise.(12)

Singapore with a population of close to 3 million is also highly susceptible to the negative impacts of sea level rise. Land reclamation programmes carried out in the past have added 6,000 ha (10 percent of the total surface area) to Singapore's original land area. The coastal zone of Singapore is intensively used by activities such as manufacturing, commerce, communications, financial and business services and construction industries. Most existing artificial coasts in Singapore (wharves, sea-walls) are likely to withstand a 20 cm rise. However, coastal erosion is also expected to increase and coast protection structures will have to be regularly maintained, elevated, repaired or relocated. (13)

These are only a few examples of well-publicized cases on which some very basic studies have been carried out. Hundreds of other cities and towns which are highly vulnerable to the threat of sea level rise have never been subject of study. The consequences of sea level rise on settlements located in lowland areas have yet to be fully imagined.


Throughout history lowlands have been optimum locations for the development of human settlements. Although technology has reduced the comparative locational advantages of lowland areas for human habitation, these areas will remain prime locations for the development of human settlements for sometime to come. This is in part due to the fact that the existing settlement patterns, which have developed through the centuries, predispose future development. Cities located in lowland areas will continue to thrive since many are already regional, national and even global hubs of industrial and economic activity. But the main reason will be that lowlands still offer many locational advantages for the development of human settlements.

Moreover, it is estimated that world population will reach the 10 billion mark within the next century. The high rate of population growth, accelerated rate of urbanization and growing poverty in the developing world will ensure that we continue to use lowlands. In fact, we can safely assume that the use of lowlands for human settlements will intensify.

However, there are serious challenges to the development of human settlements in lowland areas. Lowland environments are particularly vulnerable to development of human settlements. These areas also have particular vulnerabilities to some types of natural hazards such as seismic activity and floods. They will also be the most vulnerable in the event of sea level rise. Yet, there is every prospect that settlement of lowland areas will intensify. Under these conditions the only alternative we have is to learn to meet the challenges of building cities in lowlands.


1. Fanos, A. M. (1995) "The Impact of Human Activities on the Erosion and Accretion of the Nile Delta Coast", in Journal of Coastal Research, Vol. 11, No.3, Summer 1995, p. 821.

2. United Nations (1994) Statistical Yearbook, 39th issue, United Nations, New York.

3. Madhav, M.R. and Miura, N. "Introduction" in Lowland: Development and Management. N. Miura, M.R. Madhav and K. Koga (eds), A. A. Balkema, Rotterdam. 1994, p. 30.

4. Ibid, p. 36.

5. Armillas, I., Coburn, A. Lewis, D. and Petrovski, J. Luzon Earthquake Report, unpublished, UNCHS (Habitat) report. 1990.

6. Intergovernmental Panel on Climate Change (1990) Climate Change:The IPCC Impacts Assessment, WMO-UNEP, p. 6-3.

7. UNCHS (Habitat) Distribution and trends of growth of urban population in urban agglomerations, unpublished. 1990.

8. Edwards, S. F. "Estimates of Future Demographic Changes in the Coastal Zone". in Coastal Management. Vol.17,1989, pp. 229-240.

9. Keyfitz N. "The Effect of Changing Climate on Population", in Irving M. Mintzer (.ed.) Confronting Climate Change, Implications and Responses, Cambridge University -Press. 1992, p. 153.

10. Ibid.

11. Ascher, G. "The Case of Hamburg", in Roberto Frassetto (ed.) Impact of Sea Level Rise on Cities and Regions: Proceedings of the First International Meeting "Cities in Water", Venice, December 1989, p. 76.

12. Tamai, Y. and Ninomya, T. "Measures against Sea Level Rise due to Global Warming: Approaches of Osaka City", in Frassetto (ed), op.cit., 1991, p. 125.

13. Loke Ming Chou and G.S.Y. Lim "The Impact of Climatic Change and Sea Level Rise on Singapore" Ibid., p. 145.

Notes: This paper appears in the Volume 1, Number 1 of the Lowland Technology International published by the International Association of Lowland Technology (IALT).