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

Transcription

1 Measures against Earthquakes, T s u n a m i s a n d S t o r m S u r g e s ANMC21 Flood, Storm Surge and Tsunami Control Workshop January 22, 2013 Regarding Measures against Earthquakes, T s u n a m i s a n d S t o r m S u r g e s 1. Flood damage in the past 2. Planning and maintenance of coastal protection facilities 3. Efforts after the Great East Japan Earthquake

2 The situation of ground in coastal areas of the Tokyo Port Flood damage of the Tokyo Port in the past and height of external seawalls External seawalls in the Koto and Chuo areas are: A.P.+5.6 m(t.p.+4.47) -September, 1917 Typhoon: highest recorded water levels in the past (A.P m) - August, 1949 Typhoon Kitty (A.P m) 江東区南砂 3 丁目地下鉄東西線南砂町駅前

3 The 1917 Typhoon (September 30,1917) Photo: from Photo Collections of the Great Kanto Earthquake 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) Typhoon Kitty Typhoon No.10 (August 27 through September 5 in 1949) As the typhoon passed at high tide, a storm surge occurred in the Kanto area Serious flood at Kinshicho Shakomae of the Tokyo Toden A.P 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 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 Evacuating residents rushed in Hirai Station

4 Typhon Ise Bay 9 p.m. on September 21 through 9 p.m. on September 27 in1959 Lowest air pressure: 895 hpa Maximum wind speed: 75 m/s Casualties: 4,697 death, 401 missing, 38,921 injured Progress of Projects 1934 The Comprehensive Plan of Protection from Storm Surges was established and undertaken in the following year Typhoon Kitty (August) The Disaster Support Project for Civil Engineer was undertaken in the following year 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 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 Amount of rainfall per hour: Observed severe rain which exceeds 120 mm Accumulated amount of rainfall: Reached 2,433 mm at the maximum Lowest air pressure: 965 hpa Maximum wind speed: 35 m/s Casualties: 73 deaths,19 missing,104 injured Typhoon No.15 (9 p.m. on September 12 through 3 p.m. on September 22 in 2011) The most powerful typhoon after the war among the typhoons which made landfall in eastern Japan (strong wind) Lowest air pressure: 949 hpa Maximum wind speed: 50 m/s Casualties: 16 deaths, 2 missing, 337 injured

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) The Tatsumi Floodgate (before closing) The Tatsumi Floodgate (after closing) Situation of closing of the Tatsumi Floodgate (closing was completed at 3:06 p.m. on March 11)

7 Regarding Measures against Earthquakes, T s u n a m i s a n d S t o r m S u r g e s 1. Flood damage in the past 2. Planning and maintenance of coastal protection facilities 3. Efforts after the Great East Japan Earthquake 海岸保全の基本理念 Basic Tokyo Bay Coast Conservation Plan

8 Disaster Functions for Tsunamis and Storm Surges of the Tokyo Port Protect lives and property of the citizens of Tokyo from storm surges and tsunamis by typhoons Protect storm surges and tsunamis by external seawalls (38 km), floodgates (19 gates) and pump stations (4 stations) 水門と防潮堤で高潮津波を防御 A.P m Situation of coastal protection facilities in seacoast of the Tokyo Port A.P m A.P m 降雨河川堤防河川内部護岸運河排水機場水門強制排水防潮堤高潮 A.P+ 4.6 m 地区内の雨水は外海に強制排水雨水を強制排水伊勢湾台風級の高潮時の水位平均満潮位 (A.P.+2.1m) 高さ A.P.+4.6m~8.0m ( 潮位 + 波浪 ) 水門閉鎖時の水位高さ A.P.+3.0m Flood gate P u m p s t a t i o n Legend 外海運河 Introduction of Coastal Protection Facilities

9 Seawall Seawall

10 Seawall Parapet Wall

11 Floodgate Floodgate

12 Land Lock Land Lock

13 Pump Station Pump Station

14 Inner Embankment Embankment with care for habitat environment of aquatic organism

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 Placement Situation of Steel Pipe for Pile

18 Installation Situation of Panels Placement Situation of Concrete

19 Situation after Maintenance Image of Measures for Earthquake Resistance of Floodgates 対策液状化地盤改良 Risk of being 浸 unable 水 to close the floodgates due to disaster Maintaining functions 防護 by earthquake resistance measures 被災により水門閉鎖が不可能耐震対策により機能を維持 Measures for earthquake resistance have been implemented for floodgates preferentially where have risk of causing serious flood damage when disaster occurs.

20 General Figure of Seismic Reinforcement of Floodgates 地盤改良内水側外水側地盤改良高圧噴射撹拌深層混合処理 Regarding Measures against Earthquakes, T s u n a m i s a n d S t o r m S u r g e s 1. Flood damage in the past 2. Planning and maintenance of coastal protection facilities 3. Efforts after the Great East Japan 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 - (A.P.+3.64m ) (A.P.+3.68m ) (A.P.+3.24m ) (A.P.+3.60m ) (A.P.+3.74m ) (A.P.+3.19m ) (A.P.+3.40m ) *Values in figure are showed in the Tokyo Pail (T.P.) (T.P.+0.0 m = A.P m)

22 Point of View for Tsunamis at the Tokyo Port 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 ~1.2 平成 3 年 9 月 ( 東京都防災会議 ) 東海東南海南海 ~1.0 平成 15 年 12 月 ( 中央防災会議 ) 首都直下型地震 ~0.5 平成 17 年 7 月 ( 中央防災会議 ) 最大 1.6 元禄関東地震 7.3 ( 地殻変動量含む) 平成 24 年 4 月 ( 東京都防災会議 ) 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. Water levels by storm surges > Water levels by tsunamis Incoming wave component A.P m Seawall maintenance by the Plan for Storm Surges has enough height for tsunamis Maximum AP+8.0 m Element of the wave Height of storm surge Maximum AP+3.7 m Part of increased water level by storm surge At the bottom of the ground Tidal datum Storm surge deviation Height of tsunami Mean sea level of spring tide Tsunami and Coastal Shape 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, horseshoeshaped, and V-shaped. Low Tendency of wave height of tsunami High Bag-shaped bay Straight line-shaped bay Horseshoe -shaped bay V-shaped bay 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, which w ill decrease the strength. Thus w ave height w ill not be higher in closed-off section of bay. As for seacoast with less asperity, it is very similar to the case of horseshoe-shaped bay when sea bottom is relatively steep. How ever, when it is gradual, the strength w ill decay by the sea bottom friction and the w ave height w ill not be higher because the effects which increase wave height w ill be negated as it becomes shallow. Development of tsunami coming in to the bay is smaller compared to v-shaped bay. How ever, wave 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. 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 overlap and focused on a narrow range. Wave height amplifies and suddenly increases when it comes close to the closed-off section of bay. From the N ational Research Institute for Earth Science and Disaster Preventi on website Figures are extracted from (descripti on was partially changed for extract) the Tsunami Engineering Laborator y of Graduate School of Engineering, T ohoku U niversity website and the Research Study Report r egarding Measures against Tsunamis and Liquefaction (the si x prefectures research meeting for earthquake measures in May, 1984).

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, Recommendations 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. 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 Degree of obsolescence of facilities

24 Basic Policy of Tokyo 2 Earthquake resistance measure For seawalls 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. Water resistance measure Locate power 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 water-tightness of the opening. Take measures for estimated height of tsunami at w ater reclamation centers and others. Floodgate operation Establish tw o hubs of the High Tide Management Center w hich controls floodgates in order to operate by either one of two hubs if one of each become malfunction, and conduct multiplexing of communications netw ork as well. Allow administrators of each facility to immediately share information through using communications netw ork such as optical fiber or w ireless network that set in highly earthquake resistance sew erage pipe. Thank you for listening.