Countermeasures against urban flood in Beijing. Urban flood inundation warning and flood hazard mapping in China

Transcription

1 Countermeasures against urban flood in Beijing Fen Yang Beijing Institute of Water (BIW), China Urban flood inundation warning and flood hazard mapping in China Wang Jing China Institute of Water Resources and Hydropower Research (IWHR), China 29 th May, Korea

2 Flood control system in Beijing Information of Beijing km 2 About 20 million people 2 important reservoirs 5 main rivers Guangting Reservoir Mountain 61% Miyun Reservoir

3 Flood control system in Beijing The Central Town 1085 km 2 (7%) About 12 million people(60%) Yongding River in the west is for flood control Beiyun River in the east is for drainage Centrol Town

4 Flood control system in Beijing Flood Control Project Reservoir total 9.4billion m 3, control the flow generated by 70% mountain area. Rivers 425 Rivers with 6400 km long in the city. 143 Rivers with 2004 km long in plain, 32% regulated. 40 Rivers with 380 km long in central town, 72% regulated. controlled natural

5 小时雨量 (mm) Flood control system in Beijing Food Control Project Rainwater Pipeline 2000 km long covered 95% area of central town. most design standard is 36mm (1year), or 56mm(5year) in some important place. Rainwater Pump station Total 130 pump stations in the city, most designed suitable for 2~3 year return period 年 2 年 3 年 5 年 Design standard distribution of pump station in Central Town

6 Urban flood events Recent years, urban flood happened suddenly and frequently because of extreme weather and local sudden rainstorm, which replaced the past flood most came from the Yongding River. Extreme weather events have occurred 41 times since 2004.

7 Flood Event 7.21 Flood Detail Rainfall average rain is 170 mm in the city, which is the maximum rainfall since 1949(63year). average rain is 215 mm in Central Town, which is the maximum rainfall since 1963(49year). the rainstorm center is in Fangshan, 541 mm rainfall is the maximum recorded rainfall.

8 Effect of Current Flood Control System flood diversion and storage Safe discharging Source reduction monitoring forecast regulation Department linkage, social participation Reservoir & Sluice The city's large and mediumsized reservoirs and sluice running normal, while effectively held flood, cutting flood peak, increase water storage. Dingjiawa Reservoir Chongqing Reservoir

9 Effect of Current Flood Control System flood diversion and storage Safe discharging Source reduction monitoring forecast regulation Department linkage, social participation River & Embankment The Yongding river 200year flood control standard), Chaobai river, Beiyun river ( 50year flood control standard) and other Small and medium-sized rivers regulation (20year drainage standard) make flood through the central town normally,and ensure the urban safety. Chiwei river for flood discharge in Fangshan Beiguan Sluice open for flood discharge in Beiyun River

10 Effect of Current Flood Control System flood diversion and storage Safe discharging Source reduction monitoring forecast regulation Department linkage, social participation Stormwater utilization these structural measures are useful for increasing infiltration,storing water and reducing downstream pressure. Artificia l lake Small watershed governance Sand and gravel pit Flood volume and flood peak decreased by 36% ~ 58%, Runoff coefficient changed from 0.6~0.7 to 0.3~0.4.

11 Effect of Current Flood Control System flood diversion and storage Safe discharging Source reduction monitoring forecast regulation Department linkage, social participation Monitoring forecast Regulation According to rain forecast and upstream real-time monitoring, 5 hours in advance notice of people evacuated. Mountain disaster monitoring and early warning system broadcast 728 times, warning of more than 10,000 text messages, keep contact and well regulation when public communication interrupt, make the loss to a minimum.

12 Effect of Current Flood Control System flood diversion and storage Safe discharging Source reduction monitoring forecast regulation Department linkage, social participation Department linkage, social participation

13 The Next Focus Basic Principle Keep human safety primarily Overall plan, systemic management Integrated structural and non-structural measures coordinate the relation between the near future and the forward future

14 The Next Focus Take 4 years river governance 1460 km long Reduce water accumulation in flyover, lower elevation etc. (Low standard, human construction in river etc.)

15 storage The Next Focus flood detention facilities storage : use Sand and gravel pit, rivers, make sure under 100- year flood do not flow through the central town. reduction: in small watershed drainage unit, enforce construction of lower elevation greenbelt, permeable pavement, provide source control, slow down flow. Detention: Use of low-lying land, park green land, as storage to cut flood peak. permeable lower elevation

16 The Next Focus Flood simulating In important rivers and key areas, figure out flood submerged area, depth, duration, etc. Flood risk grading Define urban flood risk management area

17 The Next Focus Establish and improve early warning mechanism build linkage mechanism with television and other media and communications operators, expand coverage of early warning. Improve safe work mechanism for flood in key areas no entry to dangerous mountain road, go around the city roads and flyovers with water, strengthen security warning in danger zone etc. Build command platform for flood control include rainfall and flow monitoring, early warning, emergency rescue, flood dispatching, flood disaster reporting etc.

18 The Next Focus Universal education about flood prevention, risk escape, self- aid and mutual-aid, disaster mitigation etc. popular science readings, lectures, safety drills, television, radio, newspapers, network, phone message, etc.

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20 Urban flood inundation warning and flood hazard mapping in China Wang Jing Department of Water Hazard Research China Institute of Water Resources and Hydropower Research (IWHR) 29 th May, Korea

21 Contents 1 Urban inundation events in China 2 Characteristics of urban inundation 3 Urban Flood Simulation model 4 Urban Flood inundation warning 5 Flood hazard mapping in China 6 Conclusions

22 1 Urban inundation events in China July 2004, June 2011, July 2012, Beijing August 2010, Zhouqu July 2007, Jinan and Chongqing August 2008, Shanghai August 2009, Wenzhou June 2005, Wuzhou May 2010, Guangzhou

23 1 Urban inundation events in China Rainfall in Beijing Serious inundation on street and under overpass seriously, traffic tied up in city

24 1 Urban inundation events in China Rainfall in Beijing Serious inundation on street, highway in low-lying area and under overpass seriously, traffic tied up in city

25 1 Urban inundation events in China Flood from Xijiang River affected Wuzhou city on 22 nd June,2005 Inundation hazard from outside flood

26 1 Urban inundation events in China Heavy rain in Jinan on 18th July, 2007 flood spreading along streets, inundation under railway overpass and inundation in underground square

27 1 Urban inundation events in China Heavy rain in Chongqing on 17th July, 2007 Mountain city Streets were changed to rivers

28 1 Urban inundation events in China Typhoon Morakot in August, 2009

29 1 Urban inundation events in China Flash flood and debris flow in Zhouqu county in August, 2010 The death toll was 1463, and 302 missing

30 2 Characteristics of urban inundation disaster 1 The types of disasters which would cause urban inundation are multiple Including heavy rainfall, outside flood, typhoon, flash flood, debris flow, and so on 2 Many new features of urban inundation appear as the rapid development of cities Such as: inundation under road overpass and railway overpass is serious flood spreading along the street flood flows into underground space flood hazard of urban area in the lower reaches increases as the flood control standard improved in the upper reaches.

31 2 Characteristics of urban inundation disaster 3 For some cities, the waterlogging loss is severe The statistical flood and waterlogging disaster loss data of cities in Zhejiang province in 1998 and 1999 shows that the waterlogging loss occupies about 40% of total loss. 4 The main reason for death in mountain cities are flash flood and debris flow In 1991, 1293 persons died caused by flash flood and debris flow in Yunnan and Sichuan province ; In 1997, 1680 persons died caused by flash flood and debris flow in China; In 2004, the flash flood and debris flow caused by Rainne typhoon leaded to 44 persons died which is 24.2% of total death toll. 5 Secondary disasters are severe Urban flood and waterlogging disasters would affect the lifeline system of a city seriously, such as traffic, water supply, power supply and gas supply, etc.

32 3 Simulation technology: Urban Flood Simulation model

33 Flood simulation methods Hydrological model 3 Urban flood simulation model Can t reflect the spatial distribution and change process of hydraulic factors for everywhere, such as flood depth, velocity and inundation duration, etc. Hard to reflect the function of flood control projects, such as pumps, gates, drainage system Dimension description Available software Hydraulic model Digital terrain analysis method based on GIS technology 1D 1D + 2D - 2D 2D + 3D Solution of the one-dimensional St Venant equations 1D plus a flood storage cell approach to the simulation of floodplain flow 2D minus the law of conservation of momentum for the floodplain flow Solution of the two-dimensional shallow wave equations 2D plus a solution for vertical velocities using continuity only Infoworks RS(ISIS), Mike 11, HEC-RAS Infoworks RS(ISIS), Mike 11, HEC-RAS LISFLOOD-FP TUFLOW, MIKE21, TELEMAC Urban flood numerical simulation model (UFSM) developed by IWHR TELEMAC 3D CFX, FLUENT, PHEONIX The basic principle is that water moves from high to low. The simulation result can only reflect the eventual state instead of the real movement process of flood.

34 3 Urban flood simulation model Urban flood numerical simulation model (UFSM) basic principle Basic equations Continuity equation: Momentum equation: h M N q t x y M ( um ) ( vm ) Z n u u v gh g 0 1/3 t x y x h N ( un) ( vn) Z n v u v gh g 0 1/3 t x y y h The study area is dispersed by unstructured irregular meshes Finite volume method is used to solve the equations Water level is calculated on the centroid of mesh Flow is calculated on the passages of mesh

35 3 Urban flood simulation model Terrain Building Dikes Rivers Gates Pumps Drainage system Underground space

36 3 Urban flood simulation model Rainfall River flood Storm surge Dike break Combinations

37 3 Urban flood simulation model Rainfall

38 3 Urban flood simulation model Combination of rainfall and storm surge

39 3 Urban flood simulation model The different running way of the UFSM Running ways of the model Forecasting calculation + Real-time calculation Design scheme calculation Testing &adjusting calculation Before disaster During disaster After disaster

40 4 Urban flood inundation warning Urban area of Foshan city: 79.7km 2

41 4 Urban flood inundation warning QPF and QPE data Every 6 minutes: 1km 1km QPF(quantitative precipitation forecasting) grid precipitation for the 1 st, 2 nd and 3 rd hour in future QPE(quantitative precipitation estimation) grid precipitation for the last one hour, validated

42 4 Urban flood inundation warning

43 4 Urban flood inundation warning Blue 0.15~0.30m Yellow 0.30~0.50m Orange 0.50~1.00m Red >1.00m

44 5 Flood hazard mapping Practices of flood hazard mapping in China Flood mapping research started in 1986 Practices of flood hazard mapping in 1997 From 2003 to 2008: compile guidelines, pilot projects (36) New stage of flood hazard mapping from 2008 (21million RMB) project of 1st phase national flood hazard mapping commenced New stage of flood hazard mapping from 2011 (81million RMB) project of 2nd phase national flood hazard mapping commenced

45 4 Flood hazard mapping Achievements Details 1. Report on flood hazard mapping in China and abroad 2. Establish standards and regulations for flood hazard mapping 3. Technical platform and template Guidelines Technical Rules Administrative Regulation Cost Flood analysis system Flood disaster impacts and loss assessment system Flood hazard mapping system Flood risk map management system

46 4 Flood hazard mapping Achievements Details 9 flood protection areas 6 flood detention areas pilot areas 1 flooded area 2 cities (shanghai) 2 Reservoirs 5. Technical training course Three times

47 4 Flood hazard mapping Practices of flood hazard mapping in China Flood mapping research started in 1986 Practices of flood hazard mapping in 1997 From 2003 to 2008: compile guidelines, pilot projects (36) New stage of flood hazard mapping from 2008 (21million RMB) project of 1st phase national flood hazard mapping commenced New stage of flood hazard mapping from 2011 (81million RMB) project of 2nd phase national flood hazard mapping commenced

48 4 Flood hazard mapping Tasks 1. Revise the standards and regulations for flood hazard mapping 2. Improve the technical platforms 3. Flood risk analysis technology development for mountain area and pilot study 4. Flood risk analysis technology development for storm surge and pilot study 5. Real time flood risk analysis and flood hazard mapping study 6. Flood insurance system scheme study and pilot study 7. Flood hazard mapping in pilot areas 8. Pilot study on application of flood hazard maps 9. Development of flood hazard map management and application platform

49 4 Flood hazard mapping The purpose of flood hazard mapping in China In China, we hope flood hazard maps can be used in many fields Serve for the flood control and flood fighting decisionmaking at all levels of FCH Provide support for working out Flood defense emergency plan Enhance the consciousness of flood hazard mitigation of the nation Offer basic data for assessing flood losses, and so on Direct the constructions of the safety facilities for the flood detention areas, and to chose reasonable way and place for evacuating people in emergency Provide support for working out flood control planning, drainage planning

50 Historical rainfall Design rainfall

51 Dike break Inundation distribution on roads

52 Sea wall break Sea wall overflow Combination of rainfall and Sea wall break

53 4 Flood hazard mapping Flood hazard mapping in urban area in China 661 cities 4 municipalities 283 prefecture-level cities 374 county-level cities

54 5 Conclusions The urban type flood disasters are very serious in China. As Cities of China are in a stage of rapid development, the urban areas will expand continually. In future, the flood disaster risk will rise and the types will be multiple. In order to reduce the flood risk in urban area, flood simulation technology is an important non-structural measures which can provide support to flood hazard mapping, flood prevention warning and decision-making. In fact, this technology have been applied in many cities in China. The urban inundation can not be avoided completely. But we need to try our best to decrease the losses not only by improving and reconstructing our drainage system, but also considering the storage, detention, infiltration and utilization of rain water in process of infrastructure construction.

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