GISdevelopment.net ---> AARS ---> ACRS 1989 ---> Water Resources Remote Sensing Monitoring on flood damanages and its evaluation system Chen Shupeng National Remote Sensing Center, SSTCC, NLREIS, IRSA Chinese Academy of Sciences, Beijing, China Experimental flood management system in China The flood disasters in china have been being fairly rigorous from ancient times just like other Asian countries because of monsoon climate influences. Especially most flood prevention dikes and flood storage and diversion projects have been built in the middle and lower reaches of Chinese seven rivers which the following along the alluvial plains and deltas, their elevations are no more than 100 meters above the seal lever. The scales of those projects can be compared favorably with the Great Wall. Some 200,000,000 people and approximate 100 cities are protected by these water conservancy projects. Take the lower reaches of the Yellow River as an example; the dikes along the riversides up to Zhenzhou city are 400 kilometers long and 5 to 12 meters above the ground. The biggest width between the dikes is 21 kilometers. Inside the dikes there are 1, 200,000 transient people and some scattered-distributed small ' productive dikes. There are two flood storage areas, Beijin Dike Area and Dongping Lake outside the dikes. Its population is 1,300,000 and also some flood prevention dikes in the shape of island surrounded the villages. So are the other rivers such as the Yangtze River, the Hua the River the Liaohe River, and the Yongding River. It is almost like a world full of dikes in the Eastern beritages handed down through thousands years, but also the success emblem of Eastern agricultural civilization. The monitoring on dikes and flood in China is based both on the multilevel earth observation system and geographical information system (GIS). It is proved through the experiments that dikes and flood can be distinctively identified even on the image of meteorological satellite with 1.1 kilometer ground resolution and also highly effective for the real time. Them more detailed understanding about dikes and flood can be achieved by suing higher-resolution satellites such as Landsat, SPOT and other scientific and technological experiment satellites lauched by China and Japan. The real time receiving, however, is required. In recent ten years, China has been more actively engaged in aerial remote sensing monitoring including color infrared photo, infrared scanning and all - weather side-looking Radar. The Image transmission process from real time receiving to the flood Control Command Center in Beijing has been compressed within 20 hours. The daily monitoring range has been over 10,000 square kilometers. Especially that the micro digital terrain model and geographical statistics database, comprehensive analysis methods and digital simulating software have been established and applied to disaster monitoring and forecasting, its accuracy has been remarkably raised. It is proved through ten years practices that we can attain the time of flood prediction and forecasting to reduce and even avoid the losses of disasters provided that we make full use of remote sensing and GIS techniques procedure of flood information receiving, processing and analyzing within that of flood dynamic courses. Its social and economic benefits are tremendous. The remote sensing evaluation of flood damage started from the early 80's in China. The first application was on the compensation evaluation and emigration investigation for small reservoirs. It has been proved through several years' practices that both the efficiency and the accuracy can meet the needs of project planning. The real time monitoring and transmission experiments for flood disasters have been carried out in the Liaoh River, the Yongding River, the Yellow River and the Dongting. Lake since 1985. The experiment in the Jinjiang River and the Dongting Lake has been just finished in 1989. The all-weather aerial monitoring and multiple elements flood central database construction have been also realized Various regional types of flood risks and prevention countermeasures can be divided according to their different environment backgrounds such as climate, hydrology and river pattern in China. Therefore, the counter measures of flood control and disaster relief should be in line with the local conditions. Bursting type. This kind rivers flow through the plain areas with dense population and highly developed industry and agriculture. The dikes are highly built mainly for river bursting control. The riverbeds are gradually silted up, migration frequently, and so many dangerous sections are formed. Their are bursting fans and pools all over scattered outside dikes. The river formerly wildly ran on the alluival fans are artificially restrained and its antagonistic contradiction produced. With the raising of the dikes, the hidden danger becomes bigger. The flood preventing counter measures are focused on flood peak adjusting and controlling in the upper reaches to reduce the mud and sand deposition and simulate bursting plan so as in lessen the losses of disasters. For the lower reaches, the counter measures such as flood diversion, storage, cut off and river course changing are implemented so as to prevent dangerous sections from bursting. In 1988, we completed flood real time monitoring and digital terrain model base of the Yellow River between Zhenzhou and Jinan city; and all-weather monitoring and multielement geographical database of the Yangtze River between Yichang and Wuhan. Compared with the experimental monitoring system of the Yongding River between Beijing and Tianjing in 1986 and the Liaohe River between Shengyang and Yinggou, much more experiences have been obtained. Overflowing type. The river courses are divorced into distributaries in the delta areas of estuary because of the tide effect. Natural dikes are highly developed. The elevation of precipice is low. The conditions of marshiness and salinization are serious. Shipping and harbor construction are affected due to unstable lower reaches. The flood preventing counter measures are mainly to make estuary stable: to control mud and sand deposit; to extend land areas; to make irrigation system perfect 'to reduce water logging ime' to wash salt and alkali' to improve soil quality; and to irrigate under ground water back etc. The most typical type is the new delta of the Yellow River. Since 1986, we have built up micro terrain database and studied the problem of ice-flood. Although the estuary of the Yangtze River and the Pearl River have experienced reconstruction in recent thousand years, these characteristics are still remnant. Water logging type. The Lakes where rivers converge play a role in toring flood and adjusting flood peak naturally. However, because of eclaiming fields from the lakes and mud and sand depositing, the flood torage capacities are gradually lessened and flood diversion courses staffer o that the flood adjusting capability is reduced the dikes are increased. And raised and the inside terrain becomes relatively lower and lower then the outside riverbed. Since the water discharge is not affluent in ordinary lines and underground water level raised, various close wetland management and ecosystem have been formed. Therefore, they can be taken as independent original units when flood prevention and disaster relief are considered.. The gting Lake area is just made up of 39 dike arounded areas of this kind. there are the industrial and agricultural bases which need to be protected from good damages and also some transient flood diversion areas which would be given up so long as catastrophic flood coming. With the development of econimics, the industrial and agricultural bases which need to be protected live established digital terrain model for dikes and river courses to research on the all-weather monitoring plan. The Poyang Lake and the Hongze Lke have almost the same problems. Reservoir type. Reservoir is a kind of artificial lake. It is requirement to given rpedictive evaluation for reservoir flood damage. The key problems are to select dam site and to decide stair-reservoir scheme since sometimes irrigation and damage compensation could reach 40-60 percent of total investment. Meanwhile. It is requested to analyze the benefits of flood control and the requires for irrigation energy in the lower reaches of the dam. For demonstrating the Three Gorge Project of the Yangtze River, be have used SPOT, TM and aerial remote sensing images to provide landuse surveying maps ( 1:10,000) and data for the dams at different heights of 150, 175 and 180 meters. We have modified the flood damage evaluation for the Longtan Reservoir in the upper reaches of the Pearl River by using color infrared images. Finally, we have compared 21-stair development project along the Heilongjiang Amur River by using the images taken from Chinese satellite. The concept design for monitoring and evaluation system Remote sensing monitoring on flood damages and its evaluation is a technological system with multi-structure and pan-targets application. The design and implementation involves the questions of resource development the whole river basin should be taken into consideration. System project for the whole river baisn. The monitoring and evaluation information system should be constructed from macro point of view reaches of the Yellow River as an example. The thunderstorm, wind and loess in the river basin are still the main sources of mud and . For this reason, we have set up three evaluation models such as ice snow prediction in the upper reaches, shelter-forest evaluation in the while reaches and water and soil conservation in the Loess Plateau. Though Sanmen Gorge Reservoir plays an important role in flood adjusting and discharging , 25 meteorological automatic observation stations and 65 kipitation stations have been added; two radar rain observation stations up; and mocrowave communication lines from Sanmen Gorge to Zhengzhou in accordance with the thunderstorm, run off, sand output, and flowing. In the other hand, we have built up digital terrain model grid size is 50m*50m between zhengzhou and Jinan. We put the geological cross sections, landuse data within the dikes and the sociology flood storage into this model. This project we submitted has got the and cooperation from the world Laboratory (Italy). Strategic views of benefit-promoting and damage-abolishing. Many canals for flood discharging have been constructed in the north Chine planning after the catastrophic flood in 1963. Navertheless, the water usage of industry and agriculture in the alluival fan belt near the mountains is dramatically increased for more than 1,200 reservoirs have been built up one after another in the upper valleys. Not only the rivers for flood discharging have never been put into use, but also there is lack of water about 20,000,000 cubic meters annually in the North China plain. It is thus e evident that we should regard the flood as a kind of resource rather than just as disaster. The Yellow River is also not calamity disasters rather than just as disaster. The Yellow River is also not calamity disasters for the lower reaches area. In fact, the dike of the Yellow River between Zhengzhou and jinan is the excellent plain reservoir. This ribbon river course is located on the big alluival fan's axis of the Yellow River. It can be uses for gravity irrigation or urban and industrial water supply both within the north Huaihe plain and north Jiangsu plain, and to the Shegli oil-field and Quingdao city. It is not proper to just regard the Yellow River as a flood and sand discharging channel. Actually, in recent years, irrigiating area diverting from the Yellow River has been greatly increased and remarkable benefits obtained with respect to flood diversion and deposited, saline, alkali and sand land amelioration. Since the lower reaches of the Yellow River is often no flows, some large plain reserviors have been built up in order to protect the stability of the Shengli and Dagang oil-fields. With increasing of the level of flood monitoring and forecasting, it is expected that the flood can be turned from disaster to benefit. Real time ensurance and integrated utilization of the information sources. The key to build an operation system of flood prevention its integrated utilization . It has been proved through domestic sources and international experiences that the cloud charts of the meteorological satellite not only can predict thunderstorm area and its time and space endency, play a directive role in reservior;s management and floodgate opening, and to reduce flood damages; TM images and SPOT images can be aerial monitoring arrangement. Landsat TM images and SPOT images can be used to landuse change detection before and after each flood season and also update database annually. The images with 10 meters resolution from aerial real aperture radar or synthetical aperture radar can meet the needs or all-weather monitoring during flood seasons. The information about the ettlement, dikes and flood can be identified on these images. At the same ime , it is essential to create and update map database, socio-economic statistic database and historical hydrological and climatical database ince some database and historical hydrological and climatical database ince some data these database provided such as place name, transportation network idsperse ability, industrial and agricultural product and flood analyses etc. are beyond the range of remote sensing. Providing that we emprehensively make use of those information sources as mentioned baove and to construct an geographic information system which is capable of trieving, updating and analyzing, the real time monitoring and forecasting flood damage could be realized. From experimental system to operational system The operational system is different from the experimental one. Strictly eaking, the remote sensing monitoring on flood damage and its evaluation information system in China has not been out of experimental stage. It being transited towards operational system soon after. Although each. Subsystem has been installed and debugged, passed on line test and technical demonstration, and also produced remarkable socio=economic benefits, further research is still expected as following. Expert information system for flood prevention. At present, each subsystem has been jointly fulfilled by existing professionals and available instruments from various departments such as meteorological, hydroulic, remote sensing and geographical information system, so on and so forth, which are under the leadership of National Remote Sensing Center of China and of Remote Sensing Center of Hydraulic Department. It is impossible for this loose organization to carry out monitoring and evaluating tasks on seven big rivers all over the country, neither for the local hydraulic departments due to lack of enough professionals and instruments. As an agricultural country, it is necessary to organize a professional team for flood prevention which is well equipped so as to better serve the decision-making system for flood preventing and draught fighting just like the existing monitoring systems for forest-fire prevention and marine contaimination detection in our country. Real time transmission and display. The flood is proceeding in hour-speed. It requires rapid processing for remote sensing information. For instance, flood peak proceed from the Sanmen Gorge Reservoir of the Yellow River to Zhenshou city is 22 hours; from the Guanting Reservoir of the Yongding River to Beijing eight hours. It is crutial for flood control and disaster relief to save time. Because of the limits of communication Conditions, currently its still takes 17.5 hours for image processing and transmission of all weather remote sensing monitoring. The images from air-borne side-looking radar and multispactral scanner also need to be transmitted to the communication satellites through the ground receiving stations, instead of directly transmitting to the communication satellites then forward to the flood prevention command center. Data from ground seteorological and hydrological observation stations are also transmitted through microwave lines and restricted by regional conditions. Support by GIS and its composition with remote sensing information. Remote sensing monitoring are favorably accepted by the flood prevention command center and engineering departments. But it could not totally meet the requires of their decision-making and design. We have noticed that some flood discharing barriers in the riverbed such as new and old tidal flats, transienth canals, roads and dikes and so on, can be detailedly reflected under the support of GIS to create the digital microterrain model with grid size of 50*50 within the dikes, flood storage and diversion area, lake areas and delta areas. The flood prevention database taking natural fixed capitals and products of factories and mines, and landuse area statistics and products within the range of possible flood flowing areas so as to retrieve and evaluate flood damages by simulating different water levels on remote sensing images. Hydrologic and mud and sand databases should be for estimating flood flow proceed and flood storage and diversion capacities. These databases must be updated according to remote sensing data before annual flood season in order to compete with remote sensing images, to extract information and display graphic on the basis of flood bounaries so that the decision-making departments could be clear at a glance about the flood disasters. Analysis model and expert system. Some flood adjusting empirical models have been established in line with the process of run off producing of thunderstorm and various hydrological characteristics in China, and also consulting some models for run off evaluation and flood prediction in. Italy, the United States of America and Canada. With respect to remote sensing image processing and information composition, several software packages for the specific purpose of flood control have been developed such as flood boundary demarcation; water level simulation and three dimensional display; river course dynamic simulation for its change and riverbed migration; and damage evaluation within the flood area on the basis of county and city administrative units, etc. Further research will introduce land planning and management information system into ecological environment protection and resources rational development in flood storage and diversion areas to construct dynamic models. The optimization of these analysis models and their linkages will contribute much to construction of flood control and their linkages will contribute much to construction of flood control and their linkages will contribute much to construction of flood control expert system, to damages control and relief, and to homeland rebuilding. International Cooperation among mosoon Asia Like the Yangtze River and the Yellow River, there are many other big rivers in Asia originating in the roof of the world--- the Qingzang Plateau. They are the common wealth of the Asian courtiers and of the world people. Their lower reaches are also threatened by flood. There are a lot of similar scientific and technological problems to be studied, exchanges and sovled. For instance, remote sensing satellite monitoring on glacier and snow, and water resources evaluation in the Qingzang Plateau has chined remarkable economic benefits with respects to power generation and flood prevention of the Yellow River in recent five years. To my opinion. this experience maybe also suitable to the Yangtze River and other international such as wind sand prevention and treatment in the middle reaches of the Yellow River, forest shelting and water and soil conservation are being carried out under the cooperation and support from Space International Center (IDRC), Canada. The flood monitoring and its damage evaluation system of the lower reaches of the Yellow River is one of the major cooperative purpose is to comprehensively study on the following subsystem: the thunderstorm monitoring and forecasting, the flood forming mechanism , evaluation and its countermeasures. The remote sensing monitoring on the Three Gorge Project and the reservoir of the Hongshui River , the evaluation on their damages and effects on ecological environment has being highly praised by the international damages evaluation information system in China is owed a great deal to the international cooperation and support. The upper reaches of various international rivers originated in the Himalayas mountanous area are of aboundant and undeveloped hydraulic resources. Stair reservoirs have been initially built in the Lanchangjiang River, Yunan province of China. Undoubtedly , it will has a beneficial effect on flood prevention, irrigation and shipping for its lower reaches. The hydraulic resources in the Yaluzangbujiang River is much more abundant. The river has an intimate relationship with Bangladesh with respect to flood prevention and irrigation plan. Curently, a comprehensive cooperations between the two nations has been being in active efforts. Many foreign experiences are of great reference value for China such as flood prevention and cultivation plan along the seabeach in the estuary in the lower reaches fultivation plan in the lower reaches of Mae Nam Chao Phraya River of Thailand flood monitoring in the northern part of the Henghe River of India ; and irrigation plan of Pakistan etc. The remote sensing investigations which Chinese experts carried on the estuary of the seashore of Sri Lanka and Maldives were also highly efficienct. Cooperation among Asian countries has already had both a good start and a promising future. Some problems such as flood prevention irrigation and resources development of international rivers only can be solved by international co-operations on the cooperation of remote sensing monitoring on flood damage and its evaluation information system may be the first step of international information exchange of Pacific Ocean ara. References Li Huiguo et al., A preliminary Research on Flood Risk Forecasting Information System. Asian Geographer, 1987, Vol. 6, No. 2, pp. 95-102. Shupeng Chen,Pilot Study of GIS Assist to the Development Projects in the Yellow Basin. Seminar of GIS in Bangkok, Thailand, 1988.