The Green Infrastructure to control urban flooding

The Green Infrastructure to control
urban flooding in Tokyo.
Keio University
Kazunori Tanji
Hayato Shinno
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The Green Infrastructure to control urban flooding in Tokyo
Backgrounds
• The most largest city , high density cities in Asia.
Sumida Riv.
Imperial Palace
Rainbow Bri.
Shibuya
*photos cited: yunphoto.net/jp/photobase
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The Green Infrastructure to control urban flooding in Tokyo
Backgrounds
1800
1600
70
Annual rainfall(mm)
Green Space per capita(m2)
60 Tokyo 1st
1000
800
600
400
200
0
Land
Area（K
㎡）
Density
(populatio
n/K㎡）
Green
(m2/
capita)
37,555,000
8,547
4,400
2.9
Jakarta 2nd
(Jabotebek
40 )
29,959,000
3,108
9,600
-
New York
8th
30 (NY-NJ-CN)
20,661,000
11,642
1,800
29.3
London
th
20 29
Seattle, WA
133rd
10,149,000
1,738
5,800
26.9
3,208,000
2,616
1,200
-
RotterdamHague
165th
2,657,000
984
2,700
-
1400
1200
Population
(2014)
50
10
0
(TokyoYokohama)
1st to 7th are all Asian urban areas.
Largest European urban area is Moscow(15th)
*Demographia World Urban Areas10th Annual Edition May 2014
Revision
*Ministry of Land, Infrastructure, Transport
*Reference: Ministry of Land, Infrastructure, Transport and Tourism-Japan Meteorological Agency
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The Green Infrastructure to control urban flooding in Tokyo
Backgrounds
Amount of sudden sectional rainfall
is increasing
As known as “Guerrilla-Rainfall”
which makes more frequent risks of
flooding in urban-system.
*Photo cited: asahi.com
Heavy rainfall in July 2010
(Maximum precipitation per hour
69.00mm/h at Nerima district )
*http://www.jma-net.go.jp/tokyo/
Number of annual observance of precipitation in Tokyo(above 50mm/h)
10
Number of annual observance of
precipitation at Tokyo(above
50mm/h)
8
6
Linear
(Number
of annual
Changing
trend
observance of precipitation at
Tokyo(above 50mm/h))
4
2
0
1974
1979
1984
1989
1994
1999
2004
2009
**No data in 1980
*Reference: Bureau of Construction
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The Green Infrastructure to control urban flooding in Tokyo
Purposes of this The Study
Evaluation of flood risk reduction utilizing green infrastructures in Greater Tokyo Area.
Reduce risk of urban flooding.
Run off control between GI measures projected by Tokyo metropolitan government.
Expense of the GI is supposed to be improved by making incentives for residents.
Narrow
Green space
Ground floor Area
Preservation
Biodiversity
Issue
Flood Risk
New Way
Green Infrastructure
Resilience for Tokyo
Current options
River Sewer
Storage , infiltration
Health and
Relaxation
Heat Wave/Heat Shock
For aging society
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The Green Infrastructure to control urban flooding in Tokyo
Tokyo metropolitan Government’s Action Plan
• Vision and outcome for next 30 years
– No flood risk against 60mm/h,
– No inundation above floor against 75mm/h.
– No victim against heavy rain which ever recorded
• Action Plan
– By 2037, prevention of flooding against 60mm/h
– Reduce damages of inundation against 75mm/h
• Some spots(metro station and underground shopping center)
– By 2017,prevent any damage against 55mm/h
*Allocation to each infrastructure
50mm/h for sewage system . 5mm/h for rain water storage infiltration.
※Prepare Hazard map assuming the heavy rain recorded in Nagoya 114mm/h total 589mm.
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The Green Infrastructure to control urban flooding in Tokyo
Study Area
Greater Tokyo Area(GTA)
32million people 14,669 per km2.
Situated at river delta area
between Tone riv. and Ara riv.
Kanda riv. Watershed
Imperial Palace
Olympic Site Area 2020
*Cited: Tokyo Metropolitan Government
Radical expansion of urban area caused narrow green space per capita
→GTA have lost infiltration and storage function against water.
Heavy rains(50mm/h) have been more frequent.→66 times more frequent in 2005.
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Industri
al land
Green
space
Water
bodies
Land use
ResidenStudy Area Details
tial land• Stream length：24km. Watershed Area :105km2.
Road
Comme
rcial
and
public
sector
•
•
Heavy rainfall recorded in Sep. 4th 2007 112mm/h 6600houses have
suffered flooding. 97% of area is urbanized
800 housing have suffered damage of flooding(30million US$ from
1993 to 2008).
Green space※
Industrial land
Residential land
Commercial and public sector
(※crop field and park)
Road
Water bodies
Commercial and public sector
Road
Residential land
Water bodies
The Green Infrastructure to control urban flooding in Tokyo
Introduction and Backgrounds
Kanda riv. Watershed heavy rain action plan.
Improve 5mm/h by installing rain water storage and infiltration at
watershed area. Prospective amount in next 10 years 4.6mm/h
Places for installing
• Government Facility
• Educational Facility
• Pavement
• Foot pavement
*Cited: Bureau of Sewerage TMG
※Improving Shoreline protection, Control pond
and Sewer system to handling 50mm/h by
2017…not accomplished yet.
*Cited: Association for Rainwater Storage and Infiltration Technology
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The Green Infrastructure to control urban flooding in Tokyo
Why GI has not been successful in Tokyo
Tokyo is taking measures against urban environmental
problems with generating greens, especially with green
roof, however those projects lack of “compositeness”,
“synthesis” and also “approaching to private sector”.
Yuuka, Matsuda development of greener policy in Tokyo ~Speculation~ The 30th Hosei University
prize essay, award of excellence p23
City green space law(No.34)
In the urban area where green are insufficient, it is obligated to plant green in
a occasion of construct or enlarge.
Needs for Green Infrastructure??
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The Green Infrastructure to control urban flooding in Tokyo
Model and Date
• Hydrological Analysis
1. Date generation of elevation including height of
developed land as well as elevation.
2. The analysis of flow direction and stream line of
drainage.
3. The analysis of flow accumulation.
• The analysis method conducted by *Inoue
• Utilizing hydrological analysis tools added in ArcGIS
and Basic data.
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The Green Infrastructure to control urban flooding in Tokyo
Model and Date
• Hydrological Analysis
n
Fri  R S i * 
k
k
i
k 1
i
:Number of grid
k
:Types of land cover
Fri
:Water discharge in grid
R
:Precipitation
S ki
: Area of land cover grid i, type k,
i
:Water discharge coefficient grid I type k.
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The Green Infrastructure to control urban flooding in Tokyo
Scenario setting of installing measures
• Evaluate capacity of drainage, cost and local adaptability.
Measures
A:
Permeable pavement permeable pavement
of minor streets
Rain water seepage pit
B
Conventional water
storage/ infiltration
permeable pavement
technology
C：Green
infrastructure
Site and volume of installation
46％ of narrow street
Performance(㎥)
1,268.5
2,231 housing
557.7
6% of parking space
710.6
Infiltration Planter
1230m of Path way of Main Street
permeable
pavement
Rest path way of Main Street
（pathway）
100m of total circuit in public park
Vegetated Street Swale①
84.5m2 of station square
Vegetated Street Swale②
Infiltration Planter
2800m of boundary between housings
Vegetated Street Swale
Elementary school
Vegetated Street Swale
1,177㎡ of public park
Greening roof,thickness of soil
Elementary school
12cm
Vegetated Street Swale
More than 0.85m in public park
Greening roof,thickness of soil
6,208m2 of total roof of building
12cm
285.0
83.0
53.0
8.0
650.0
64.0
1.0
8.0
0.0
124.0
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infiltrate side ditch
Downspout disconnection refers to the
rerouting of rooftop drainage pipes to
drain rainwater to rain
barrels, cisterns, or permeable areas
instead of the storm
sewer. Downspout
disconnection stores stormwater
and/or allows stormwater to infiltrate
into the soil. This simple practice may
have particularly great benefits in cities
with combined sewer systems.
Planter Boxes
Planter boxes are urban rain
gardens with vertical walls
and open or closed bottoms
that collect and absorb
runoff from
sidewalks, parking lots, and
streets. Planter boxes are
ideal for space-limited sites
in dense urban areas and as
a street scaping element.
Bioswales
Bioswales are vegetated,
mulched, or xeriscaped chann
els that provide treatment and
retention as they move
stormwater from one place to
another. Vegetated swales
slow, infiltrate, and filter
stormwater flows. As linear
features, vegetated swales are
particularly suitable along
streets and parking lots.
Green Streets and Alleys
Green streets and alleys
integrate green infrastructure
elements into the street and/or
alley design, design to store,
infiltrate, and evapotranspire
stormwater. Permeable
pavement, bioswales, planter
boxes, and trees are among the
many green infrastructure
features that may be woven into
street or alley design.
Green Roofs
Green roofs are covered with
growing media and vegetation
that enable rainfall infiltration
and evapotranspiration of stored
water. Green roofs are
particularly cost effective in
dense urban areas where land
values are high and on large
industrial or office buildings
where stormwater management
costs may be high.
Permeable Pavements
Permeable pavements are paved
surfaces that infiltrate,
treat, and/or store rainwater where
it falls. Permeable pavements may
be constructed from pervious
concrete, porous asphalt,
permeable interlocking pavers,
and several other materials. These
pavements are particularly cost
effective where land values are
high and where flooding or icing is
a problem.
Result1 Water Road in the district
This precise analysis includes Sea level, height of city block and height of roads
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The Green Infrastructure to control urban flooding in Tokyo
Results
• There are three paths of drainage
• These three paths join together at some points
→many flooding are reported at these
points
• The rainwater flowed into the area with
narrow minor streets in a house crowd place
through rain water paths.
• These narrow and minor streets are not able
to drain.
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The Green Infrastructure to control urban flooding in Tokyo
Results2. Performance
Million $
1,000ha
8.00
30
Private facilities
25
Public facilities
7.00
Private facilities
Public facilities
6.00
20
5.00
15
4.00
3.00
10
2.00
5
1.00
0
0.00
Scenario A Scenario B
Scenario C
Comparison of Required area
in each scenario
Scenario A Scenario B Scenario C
Required cost
in each scenario
sufficient land area for
handling + 5mm/h rainfall
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The Green Infrastructure to control urban flooding in Tokyo
Conclusion
• Green Infrastructure can be installed on roofs,
garden, parking place, of Public building
however in terms of required installation area
and total cost for GI is inferior to the others.
• GI can be attractive if some incentives is
supposed to be designed for private sector to
pay additional cost.
• Further studies are needed for GI in mega
cities of Japan and East Asia.
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The Green Infrastructure to control urban flooding in Tokyo
Out ｃome
• For more effective operation
– Precise detailed plan
• Planning should be along the stream(complicated),
not just planning by altitude. It is important to
observe and making policy decision with microscaling.
– General idea and systemized Options that can be
utilized at narrow city blocks
• 4A:Anyspace (Compact), “Attachable”,
“Attractive”, “Attend-able”
– Make incentives as well as funding should be designed for Private
Sector.
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Suggestion “TUBONIWA” Traditional Spot Garden
• “TUBO”：１TUBO(1.8m×1.8m)narrow space. “NIWA”：Garden
• “TUBONIWA” is one of the type of garden which is purposing the
possibility to feel the nature even in the narrow space.
“TUBONIWA” built in Gate
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“TUBONIWA” built in a Bathroom
To spread the TUBONIWA . We don’t need nothing more but a
bit amount of space and catchy beautiful design.
The Green Infrastructure to control urban flooding in Tokyo
Options and their capacity
Measures
①Greening roof,thickness of soil 12cm
②Greening roof with perlite 30cm
③Vegetated Street Swale
④Infiltration Planter
⑤turf
⑥planting
⑦bare land
⑧developed land
⑨permeable pavement（pathway）
⑩permeable pavement（road）
⑪permeable interlocking concrete block
⑫infiltrate side ditch
small：0.3m×0.3m
⑬Rain water seepage pit
medium：0.6m×0.6m
large：1.0m×1.0m
Small：0.25m
⑭Rain water seepage trench
Medium：0.40m
Large：0.75m
Performance
of infiltration
0.020
0.060
0.532
0.232
0.050
0.050
0.002
0.002
0.020
0.050
0.020
0.100
0.250
0.618
1.710
0.247
0.365
0.658
Unit
㎥/㎡
㎥/unit
㎥/m・hr
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