Contents
1 Outline of Sewerage in TOKYO

Sewerage in Tokyo

2

Major Policies of the Bureau of Sewerage

3 Inundation Measures in TOKYO

Sewerage of the 23 wards in Tokyo
Item

Overall project plan

1 Outline ofUkima

Shingashi

23 wards

Total sewered area
(Planned)

57,800ha

Sewered population

8.859million

Nakagawa
Miyagi

Sewerage in TOKYO

Percentage of sewered
population

KosugeMikawashima
NakanoSunamachi

Total amount of water
treated per day
Total length of sewers

15,800km

No. of water reclamation
center13

No. of pumping stations

83

Capacity
Kasai

Shibaura

AriakeMorigasaki

13 Water Reclamation
Centers which protect thewater environment of Tokyo

100%
Mainly acombined system
6.224 million
m3/day4.635 million
m3/daySewerage system

OchiaiReconstruction works

Major Policies of the Bureau of Sewerage

16,000

単年度延長
500

10,0008,000

Sewers that has exceeded
statutory useful life

6,000

200
4,000

100
2,000

平成20年

平成17年

平成 8年

平成14年

平成 5年

平成 2年

平成11年

昭和62年

昭和59年

昭和56年

昭和53年

昭和50年

昭和47年

昭和44年

昭和41年

1959

昭和38年

昭和35年

昭和32年

昭和29年

昭和26年

昭和23年

昭和20年

昭和17年

昭和 8年

昭和14年

昭和 5年

01912

大正 4年0大正元年(Reclaimed Wastewater, Sludge, Heat)

12,000400300・Advanced Treatments
・Utilization of Resources

14,000

Sewers累計延長
massively installed after
the rapid economic growth

昭和11年

・Improvement of Combined Sewer Systems

Total length of累計（ｋｍ）
Sew er s( km)

東京都（区部）管渠延長600

昭和 2年

・Earthquake Countermeasures

L en g t h o f Sew er s

大正 7年

・Inundation Measures

An increasing number of facilities
年度別（ｋｍ）
installed per year(km)

大正13年・Reconstruction Works

大正10年

2

Deteriorated Sewers

20091

Reconstruction works
Under Reconstruction

After Reconstruction

3 Inundation Measures in TOKYOSPR(Sewage Pipe Renewal)Method

SPR Method adopted
in many countries
 Sewers survey with TV Cameras

Gravity Flow & Pump

Drainage Area

3-1

Inundation and Role of Sewerage・Role of sewers : To prevent cities from inundation by collecting all rain water fallen
in cities and discharging to rivers
・Inundation caused by inner water flooding : Lack of capacity of sewers or receiving rivers

SAITAMA Pref.

＜東京都＞

Storm Water Sewers & Pumping Stations

CHIBA Pref.

Inner Water Flood

＜東京都＞
＜東京都＞
＜東京都＞
約250億円洪水氾濫等の約250億円
約250億円
約250億円洪水氾濫等の洪水氾濫等の洪水氾濫等の内水氾濫以外に内水氾濫以外に内水氾濫以外に内水氾濫以外による被害額
よよ
るる被害額
被害額
被害額
よるriver

TMG HQsewerpumpingstation
荒川

12%
12%12%12%＜Outer Water Flood＞
Damage caused by Outer Water Flood

多摩川Tokyo Bay

KANAGAWA Pref.

LEGEND
Gravity Flow Area
Pump Area
Separated Sewer Area

Discharge is restricted due to highwater level of rivers

Drained Storm Water Exceeding
Capacity of Sewers

Outer Water ＜東京都＞
Damage
約2 5 0 億円

洪水氾濫等の内水氾濫以外による%被害額

12To be inundated by dikebreaking or overflow whenwater level of a river isrising

Total amount of flood damage
FY 98～07 at Tokyo

12%

InnerWater
内水氾濫にDamage
よ る 被害額88%
88%

Dikebreaking

1.6 Billion US$

内水氾濫に内水氾濫に内水氾濫によよる
るる被害額
被害額
被害額
よ約1 , 3 5 0 億円

内水氾濫に
88%
88%
88%
よる被害額

約1,350億円
約1,350億円
約1,350億円

88%
約1,350億円
3-2 Present Situations & Tasks～ Decrease of Infiltration by Expansion of Urbanization

Inundation Damage Occurs even in Sewered Area
・・・“Urban Inundation”（1940’s）

Enhancement of inundation measures
Frequent urban flood disasters
 The amount of storm water running off has increased due to ongoing urbanization.
 Super typhoons and localized torrential rains frequently occur.

（Present）

 Hollows or the base of hills are subject to being inundated whenever it rains heavily.

Ground Covered withConcrete, Asphalt, Buildings,and etc.

Date

Decrease of Infiltration⇒ Overflow from Sewers

Half of Storm Water
Comes into Sewers

１.６ times 80% of Storm Water

Meteorologicalphenomenon

Maximum hourly
rainfall(mm/h)

Above and below floor
level inundation(No. of buildings)

Oct. 13, 2003

Heavy rain62253

Oct. 9, 2004

Typhoon No. 2273993

Oct. 20, 2004

Typhoon No. 23

45

Aug. 15, 2005

Heavy rain

79191

Sep. 4, 2005

Heavy rain

112

5,048

Aug. 5, 2008

Heavy rain

59

171402

Comes into Sewers
Upgrade of Sewer DesignCapacity2

～ Current Increase of Inundation Risk ～3-3

Increase of Risk on Inundation
・Urbanization Expanding to the Area Vulnerable to Inundation such as Low Land and Hollows
・Frequent Occurrence of Rainfall over Design Rainfall Intensity in Recent Years・ Multiple Land Use such as Underground Shopping Center, Basement, and so on.

400350300
250200150100

S51～63500

平均168 回H1～H10
平均

184回

H11～20
平均

231 回

S76 77 78 79 80 81 82 83 84 85 86 87 88 89
H 90 91 92 93 94 95 98 97 98 99 00 01 02 03 04 05 06 07 08

51 52 53 54 55 56 57 58 59 60 61 62 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20［year］

Number of Underground
Shopping Center
Floor area

Floor Area (10,000m2)［frequency/year］

Number of Underground Shopping Centre Recently rainfall over 50mm/hr , which isthe design rainfall, is increasing !

Increaseof Underground
Shoppingcenter(Nation Wide Data : Meteorological Agency)

Change of Underground Shopping Center（Ref : Kajima Technical Research Center)

Enhancement of inundation measures
Conceptual drawing ofinundation measures

Installation of stormwater
infiltration inlets

Installation of bypass pipes and additionalsewers
Rainfall infiltration
facilities(on the premises ofhouses)

Construction of Facilities
1 To Drain as fast as possible
Increasing Capacity(50mm/hr-50% ⇒50mm/hr-80%)
Pumping Stations
Sewers (Trunk Sewers, Branch Sewers)
2 To introduce Infiltration system
3 To Reserve Storm Water
Construction of Storm Water Reservoirs
4 To Upgrade Capacity to Protect UndergroundRainfall Intensity 50mm/hr ⇒75mm/hr

Preparation against
Disaster by Residents
or Manager

1

To Stop Storm Water
Coming into
Underground Space・ Preparation of Stop Log
or Sandbag1Risk Communicationyear

Frequency of Rainfall over 50mm/hr per Year

Comprehensive Inundation Measures

1 Announcement of Risk Information
Publication of Hazard Map
Warning Water Level of Trunk Sewers“ AMESH” Rainfall Information System by Combination of Rader and rainfall Gauge

Reinforcement of risk communications concerning inundation
 Provision of information on rainfall

 Information accessible via mobile phone(boosted discharge capacity by providing sewers)

AMESH : http://www.gesui.metro.tokyo.jp/(Rainwater on the premises of houses will
be infiltrated to reduce the amount ofrainwater entering sewers.)

Installation of a rainwater
reservoir for flood control(storage of rainwater exceeding sewer capacity) Distribution of information on trunk sewer
water levels to the wards via an optical fibernetwork

 Wada Yayoi Trunk Sewer
provided along the Kanda River, which floods extensively(inner diameter of 8.5 m; storage capacity of 150,000 m3)

Increased diameter ofbranch sewers

Installation of storm
water storage pipes

Water levelindicator for theMomozono-kawatrunk sewer whichused to be a river(increased discharge capacity
by replacing sewers)(construction of a pumping station,provision of additional pumps, etc.)

Installation of a trunk sewer
for rainwater(in response to increasing amount ofrainwater discharge)

Year

No. of access

2005

About 6.5 million

 Minamisuna Rainwater Reservoir

2006with multiple residential units above forthe effective use of space(storage capacity of 25,000 m3)

2007

About 9.6 million

2008

About 15.7 million

Kanda River Preparation and publication of hazard maps

(storage of rainwater
exceeding sewer capacity)

Boosted capacity of a pumpingstation

About 7.6 million
Legend(inundationdepth) Hazard map of drainage areas of the Kanda River3