T s u n a m i s a n d S t o r m S u r g e s

(1)

Me a s ur e s ag a ins t Ea rt hq uak e s ,

January 22, 2013

ANMC21

Flood, Storm Surge and Tsunami Control Workshop

1. Flood damage in the past

2. Planning and maintenance of coastal

protection facilities

3. Efforts after the Great East Japan

Earthquake

Regarding Measures against Earthquakes,

(2)

The situation of ground in coastal areas of the

Tokyo Port

江東区南砂3丁目

地下鉄東西線南砂町駅前

-September, 1917 Typhoon: highest recorded water levels

in the past

(A.P.+4.21 m)

- August, 1949 Typhoon Kitty

(A.P.+3.15 m)

External seawalls in the Koto and Chuo areas are:

A.P.+5.6 m（T.P.+4.47）

○

Flood damage of the Tokyo Port in the past

(3)

The 1917 Typhoon

(September 30,1917)

・

Lowest air pressure:

953 hPa

・

Maximum wind speed:

40 m/s

・

Damage situation:

1,324 people dead and missing (500 people

in Fukagawa and Shinagawa)

Over 3,100 boats, ships and barges turned over (Yokohama

Port)

Photo: from ‘Photo Collections of the Great Kanto Earthquake’

Typhoon Kitty

Typhoon No.10 (August 27 through September 5 in 1949)

・

Outbreak period:

9 p.m. on September 21 through 9 p.m. on

September 27 in 1959

・

Air pressure:

986 hPa (lowest: 956 hPa)

・

Maximum wind speed:

110 knot (analyzed by the US Navy)

・

Casualties:

135 deaths, 25 missing, 479 injured

・

As the typhoon passed at high tide, a

storm surge occurred in the Kanto area

・

A.P.+3.15 m was recorded in Tokyo

・

Widespread damage to boats and

ships occurred in the port and harbor

・

Out of 90 boats and ships at anchor at

the Yokohama Port, 26 sank

Serious flood at Kinshicho Shakomae of the Tokyo Toden

(4)

Typhon Ise Bay

9 p.m. on September 21 through 9 p.m. on September 27 in1959

・

895

hPa

・

Maximum wind speed:

75

m/s

・

Casualties:

4,697 death, 401 missing, 38,921

injured

1934

The Comprehensive Plan of Protection from Storm Surges

was established

and undertaken in the following year.

1949

Typhoon Kitty

(August) ⇒

The Disaster Support Project for Civil Engineer

was

undertaken in the following year.

1956 Establishment of

the Coast Act

1959

Typhoon Ise Bay

(September in Nagoya area)

⇒

The Plan for Special Measures against Storm Surges in Tokyo Port

was established

and undertaken in the following year.

1966

Seawalls for Koto and Chuo areas were completed

(1965)

Inner embankment for Koto area was undertaken

(1966)

1999

Partial amendment to the Coastal Act

(May

) ‘Protection

＋

Environment

＋

Utilization’

2004

Establishment of the Basic Tokyo Bay Coast Conservation Plan

(August)

2007

Emergency Maintenance Plan for Coastal Protection Facilities of Tokyo Port

(March)

(5)

Typhoon No.12

Outbreak period:

9 a.m. on August 25 through 3 p.m. on September 5 in 2011

・

Lowest air pressure:

965 hPa

・

Maximum wind speed:

35 m/s

・

Casualties:

73 deaths,19 missing,104 injured

Amount of rainfall per hour:

Observed severe rain which exceeds

120 mm

Accumulated amount of rainfall:

Reached 2,433 mm at the maximum

Typhoon No.15

(9 p.m. on September 12 through

3 p.m. on September 22 in 2011)

・

949 hPa

・

Maximum wind speed:

50 m/s

・

Casualties:

16 deaths, 2 missing, 337 injured

The most powerful typhoon after the war

among the

typhoons which made landfall in eastern Japan

(strong

wind)

(6)

Tsunami Generated by the Great East Japan

Earthquake

(March 11, 2011)

The TMG Bureau of Port and Harbor

’

s Response

(situation of closing of the Tatsumi floodgate on March 11)

Situation of closing of the Tatsumi Floodgate

(closing was completed at 3:06 p.m. on March 11)

The Tatsumi Floodgate

(before closing)

The Tatsumi Floodgate

(after closing)

(7)

Earthquake

Basic Tokyo Bay Coast

Conservation Plan

(8)

A.P+ 5.6 - 8.0 m A.P+ 5.6 - 6.3 m A.P+ 5.1 - 6.3 m A.P+ 4.6 m 防潮堤水門排水機場高潮降雨降雨河川堤防内部護岸河川運河強制排水強制排水地区内の雨水は外海に強制排水水門と防潮堤で高潮・津波を防御防潮堤水門排水機場高潮降雨降雨河川堤防内部護岸河川運河強制排水強制排水防潮堤水門排水機場高潮降雨降雨河川堤防内部護岸河川運河強制排水強制排水防潮堤水門排水機場高潮降雨降雨河川堤防内部護岸河川運河強制排水強制排水地区内の雨水は外海に強制排水水門と防潮堤で高潮・津波を防御運河平均満潮位（A.P.+2. 1m）高さ A.P.+3.0m 伊勢湾台風級の高潮時の水位水門閉鎖時の水位雨水を強制排水外海高さA.P.+4.6m∼8.0m （潮位＋波浪）

Protect storm surges and tsunamis by external seawalls (38 km), floodgates (19 gates) and pump stations (4 stations)

Protect lives and property of the citizens of Tokyo from storm surges and tsunamis by typhoons

Situation of coastal protection facilities in seacoast of the Tokyo Port

Disaster Functions for Tsunamis and Storm Surges of the Tokyo Port

Legend

Flood gat e P u m p s t a t i o n

Introduction of Coastal Protection

Facilities

(9)

Seawall

(10)

Seawall

(11)

Floodgate

(12)

Land Lock

(13)

Pump Station

(14)

Inner Embankment

(15)

Image Figure of

Embankment for Crabs

High Tide Management Center

(Tatsumi)

(16)

High Tide Management Center

(Tatsumi)

Construction of Coastal

Protection Facilities

(17)

Measures for Earthquake

Resistance Embankment

for

Placement Situation of Steel

Pipe Pile

(18)

Installation Situation of Panels

(19)

Situation after Maintenance

液状化

地盤改良

浸水

被災により水門閉鎖が不可能

防護

耐震対策により機能を維持

対策

液状化

地盤改良

浸水

防護

液状化

地盤改良

浸水

防護

対策

Risk of being unable to close the

floodgates due to disaster

Maintaining functions by

earthquake resistance measures

Measures for earthquake resistance have been implemented for floodgates preferentially

where have risk of causing serious flood damage when disaster occurs.

Image of Measures for Earthquake

Resistance of Floodgates

(20)

【地盤改良】

外水側

内水側

地盤改良

・高圧噴射撹拌

・深層混合処理

General Figure of Seismic Reinforcement

of Floodgates

Earthquake

(21)

毛長川

Estimated Damage by the Earthquake Division of the Disaster Prevention Council of Tokyo

– Distribution of seismic intensity

-Estimated Damage by the Earthquake Division of the Disaster Prevention Council of Tokyo

– Height of tsunamis

-*Values in figure are showed in the Tokyo Pail (T.P.) (T.P.+0.0 m = A.P.+1.134m)

（A.P.+3.64m）（A.P.+3.60m）（A.P.+3.68m）（A.P.+3.24m）（A.P.+3.74m）（A.P.+3.19m）（A.P.+3.40m）

(22)

Point of View for Tsunamis at the Tokyo Port

Seawall maintenance by the Plan for Storm Surges has enough height for tsunamis

■

Water levels by storm surges＞Water levels by tsunamis

According to simulation results, height of tsunami is 1.6 m at the maximum (including value of crustal movement). Expected highest tide levels when tsunami comes is: mean sea level of spring tide A.P.+2.1m ＋height of tsunami 1.6m ＝A.P.+3.7m

This is lower than expected water levels at storm surge.

■

Simulation results regarding Tsunamis

想定地震マグニチュード津波高（ｍ）出典大正関東地震

7.9

０．９∼１．２平成３年９月（東京都防災会議）東海・東南海・南海

8.5

０．０∼１．０平成１５年１２月（中央防災会議）首都直下型地震

7.3

０．０∼０．５平成１７年７月（中央防災会議）元禄関東地震

7.3

（地殻変動量含む）最大１．６平成２４年４月（東京都防災会議） Maximum AP+3.7 m

Part of increased water level by storm surge

Incoming wave component

At the bottom of the ground

Tidal datum

Mean sea level of spring tide Storm surge deviation Element of the wave Maximum AP+8.0 m Height of storm surge Height of tsunami A.P.4.1 - 5.1 m

Wave height of tsunami in closed-off section of bay generally tends to become higher in the order below when the shape of bay is grouped into four general categories of bag-shaped, straight line-shaped, horseshoe-shaped, and V-shaped.

・From t he N ational Res earc h I nstitute for Earth Science and Disast er Preventi on websit e

・Figures are extract ed from (descripti on was partially changed f or extrac t) the Tsunami Engineering Laborator y of Graduat e Sc hool of Engineering, T ohoku U niversit y website and the Research Study Report r egarding Meas ures against Ts unamis and Liquef action (the si x prefec tures research meeting f or earthquake measures in May, 1984).

T e n d e n c y o f w a v e h e ig h t o f ts u n a m i High Low

The strength of tsunami comes from the ocean w ill be focused on both sides. Since it is squeezed into a narrow area suddenly,

energy of tsunami w ill overlapand focused on a narrow range.

Wave height amplifies and suddenly increases w hen it comes close to the closed-off section of bay.

Development of tsunami coming in to the bayis smaller compared to v-shaped bay. How ever, w ave height w ill become higher and amplify w hen it comes closer to the closed-off section of bay. When a distant tsunami occurs, it w ill be larger than v-shaped bay in the closed-off section of bay.

As for seacoast w ith less asperity, it is very similar to the case of horseshoe-shaped bay w hen sea bottom is relatively steep . How ever, w hen it is gradual, the strength w ill decay by the sea bottom frictionand the w ave height w ill not be higher because the effects w hich increase w ave height w ill be negated as it becomes shallow .

Width of strength of tsunami w hich coming in from mouth of bay becomes narrow er in the entrance of the bay. Since the closed-off section of the bay is w ide, the strength of tsunami w ill disperse after it comes into the bay. Also,sea bottom friction w ill increase as depth of the sea becomes shallow, w hich w ill decrease the strength. Thus w ave height w ill not be higher in closed-off section of bay.

■V-shaped bay ■Horseshoe -shaped bay ■Straight line-shaped bay ■Bag-shaped bay

Tsunami and Coastal Shape

(23)

Recommendations on how flood control measure associated with earthquakes and tsunamis should

be taken (summary

)

・A Technology Verification Committee for Flood Control Measure Associated with Earthquakes and Tsunamis (chairman: Chuo University professor Tadashi Yamada) which includes academic experts made recommendations, from a point of view of results of emergency surveys, on measures that Tokyo should take from here on.

・Recommendations were summarized in August, 2012.

For tsunami

○According to the estimated result of the Disaster Prevention Council of Tokyo, water levels of tsunami will be lower than height of seawalls by storm surge plan, so safety will be secured by originally planned height.

Earthquake resistance measure

○For coastal area and lowlands where the ground is low and have a possibility of flood damage, measures for largest possible earthquake ground motions such as magnitude 8.2 subduction zone earthquake should be taken for the future.

Water resistance measure

○Measures should be implemented in order to maintain functions of electricity and mechanical equipment of floodgates, pump stations, pump locations, and water reclamation centers when flood occurs due to damage of seawalls and floodgates.

Floodgate operation

○Introduction of remote control system should be considered in order to make sure the prompt closing of floodgates, land locks, and tide gates for storm surge that require operation at actual places.

○Enhancement of functions, such as maintenance of backup facilities and multiplexing of communications network, should be conducted for facilities that the remote control systems has already been introduced.

For promotion of measures from here on

○

Measures should be promoted based on the new results of considerations by the

Central Disaster Prevention Council regarding earthquakes and tsunamis.

Recommendations

Basic Policy of Tokyo 1

Goal

○

Implement measures to maintain functions of each facility and prevent flood by tsunamis

when magnitude 8.2 subduction zone earthquakes occur.

Point of View

○

Changing height of seawalls is not necessary as the height of seawalls of the current plan has

enough height for estimated tsunami height.

○

Enhancement for earthquake resistance should be conducted for magnitude 8.2 subduction

zone earthquakes estimated by the Disaster Prevention Council of Tokyo.

○

Prevent flood for electricity and mechanical equipment for each facility.

○

Promote maintenance by considering priority.

・

A large scale of lower ground area such as area below sea level

・

Low ground behind seawalls

(24)

Basic Policy of Tokyo 2

Earthquake resistance measure Water resistance measure Floodgate operation

○For seaw alls and embankments, maintain functions w hich prevent flood by conducting reinforcement for damage and subsidence.

○For floodgates, maintain function of opening and closing of the gate by conducting reinforcement of gateposts and enhancement of fixing of equipment.

○For pump locations, maintain w ater pumping function by conducting earthquake resistance for building frame.

○Locate pow er receiving and transforming equipment and emergency pow er system for floodgates and pumps higher than storm surge height.

○For equipment combined w ith facilities such as pumps, maintain their functions by w ater-tightness of the opening.

○Take measures for estimated height of tsunami at w ater reclamation centers and others.

○Establish tw o hubs of the High Tide Management Center w hich controls floodgates in order to operate by either one of tw o hubs if one of each become malfunction, and conduct multiplexing of communications netw ork as w ell.

○Allow administrators of each facility to immediately share information through using communications netw ork such as optical fiber or w ireless netw ork that set in highly earthquake resistance sew erage pipe.