Climate Exchange

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Towards climate risk resilient cities:

spatially explicit land-use scenarios

Yoshiki Yamagata, Center for Global Environmental Research,

National Institute for Environmental Studies, Japan

s we face a future of human-induced increase of green-

house gases in the atmosphere, we need to prepare

for climate change impacts that will see tempera-

tures increasing 3-5° C since the industrial revolution. In

the process of urban planning, it is necessary to consider not

only climate change mitigation but also adaptation measures.

The Tokyo Metropolitan Area, which is still by far the largest

megacity in the world, is extremely vulnerable against climate

risks (especially flooding) because a large part of important

infrastructure is concentrated near the bay area. Climate

research projects increasing flooding risks in Tokyo due to

climate change as well as tsunamis from large earthquakes in

the future. We need to consider appropriate land uses that are

more resilient to climate risks.

Recently, in connection with the planning of low-carbon cities,

many urban planners have become aware of the ‘compact city’

concept. Because sprawled cities with low residential density

rban

ssues

depend inevitably on heavy car use, it is suggested

that a reduction in CO

emissions could be achieved

by changing urban form to a more compact style,

to increase the use of public transport. We should

also point out that compact cities are not necessarily

more vulnerable to climate and disaster risks.

We need to carefully analyse the implications of

different land-use scenarios. For instance, it is impor-

tant to consider the co-benefits of climate change

mitigation and adaptation measures. In order to come

up with an appropriate urban design in terms of

climate risk management, we need a tool that allows

us to conduct city-level scenario assessments. For

that purpose, we have created a new, spatially explicit

urban land-use model.

Urban development in Tokyo

Before looking into the future, let us look back on the

past 100 years of urban development in the Tokyo

Metropolitan Area. The images on this page show the

historical growth of the urban built-up area, estimated

from

The National Atlas of Japan

The maps were

digitized for the years 1888, 1914, 1946 and 1975,

then geographically registered, and urban areas were

delineated using a geographic information system

technology for conducting quantitative analyses. The

images illustrate the dynamic urban centre expan-

sion pattern, especially after the Second World War

(1950s) and the rapid suburbanization during the

fast gross domestic product growth period (1970s).

Urban expansion has continued and reached almost

a maximum during the bubble period (1990s). Since

2010, Japanese society has entered the phase of the

‘over-aged, population decreasing period’. One of the

most difficult urban issues in the near future will be

to consider how to achieve this shrinking phase in

a sustainable manner. It is financially impossible to

maintain all urban infrastructures equally, so we need

to make wise urban land-use scenarios.

Land-use scenarios and the heat island effect

The Center for Global Environmental Research,

National Institute for Environmental Studies urban

economics model calculates the interaction between

land, transport and energy use in cities. It describes

Source: The National Atlas of Japan, GSI

(a) 1888

(b) 1914

(d) 1975

Spatial explosion of the Tokyo Metropolitan Area, 1888-1975