Flood disaster is one of the most serious natural disasters, especially in the urban environment. Because of the large population and dense and expensive facilities, the consequences of flood disaster are particularly serious. The success of urban flood control system construction is directly related to urban economic development and people's personal safety, so governments at all levels attach great importance to the construction of flood control system. 3S has advantages in real-time location, acquisition, analysis and management of geospatial information, and can play an important role in urban flood control.
Construction of Shenzhen Flood Control Management Support System
Shenzhen is located in the central coastal area of Guangdong Province, bordering Lingdingyang in the Pearl River Estuary in the west, Zhongshan City and Zhuhai City in the south, Shenzhen River in the south, Daya Bay in the east, Pinghai Peninsula in Huidong County, and Dongguan City and Huiyang City in the north. Shenzhen is close to the South China Sea, which is an area prone to typhoons and floods. The floods in Shenzhen are mainly caused by heavy rain. The city's landforms are mainly hills, with 62% of the area with a ground slope greater than 3 degrees. The main rivers are small and the basin area is less than 400 square kilometers. Shenzhen is a humid area in the south, with large output and flow. In addition, the average slope of the river is relatively large, belonging to small and medium-sized rivers with mountains and streams. This characteristic of the basin makes the average confluence time of the basin shorter, the flood peak discharge modulus larger, and the flood process is sharp, usually several hours, which is manifested by the rapid rise and fall of the mountain stream. In the 1990s, there were two floods in Shenzhen, each of which caused economic losses of more than one billion yuan. The urban flood control management support system based on 3S technology organically integrates the existing water conservancy engineering measures and non-engineering measures, forming a complete Shenzhen flood control management support system. (Figure 1)
The system has the following characteristics:
(1) organically integrates several modules, such as automatic monitoring of flood control facilities, flood forecasting, flood dispatching, flood control information service and flood control consultation, and realizes an information integration system that meets the business processes of different user groups, such as leadership decision-making layer, business processing layer and technical maintenance layer.
(2) The application modes of spatial database, comprehensive database, conversion standard, technical development standard and data standard involved in the construction of urban flood control management support information system are explored.
(3) The construction mode of flood control management support system for urban buildings, residential areas and commercial intensive areas based on large-scale topographic map and integrated with high-resolution remote sensing image basic spatial database is explored.
(4) Considering many factors as a whole, such as reservoir discharge, drainage in key flood control areas, opening and closing of river sluice, tidal level where rivers enter the sea, flood detention capacity of flood detention areas, etc., so as to realize the visual, interactive real-time or quasi-real-time decision-making ability of urban flood control management.
(5) The real-time, security and practicability of the system are enhanced by taking GIS as the main line and combining GPS positioning, PDA wireless communication, wireless video transmission, remote automation control and other related technologies.
master design
Flood control management support system is a complex system engineering including communication and information technology, flood control and disaster relief management and decision-making, flood forecasting and scientific dispatching, involving flood control and water conservancy project, real-time monitoring and communication system, geographic information system, remote sensing system, network distributed information processing system, large database, professional model, calculation and analysis, visual simulation, decision support media and environment.
According to the hierarchical structure, the system is divided into decision-making layer, business layer, management and maintenance layer and technical support layer (Figure 3), which corresponds to the three-layer structure (B/A/S) under the network environment, directly facing the needs of different user groups for the system, and realizing the functions of flood control business processing and management decision-making.
Fig. 2 Related interfaces of Shenzhen flood control management support system
Figure 3 General idea of system design
In the construction of flood control management support system, the three-layer structure of "database+management and maintenance layer/technology layer/business layer+decision layer" is taken as the basic framework, and the geographic information system is taken as the core platform to carry out the design and construction of comprehensive database, spatial database, application system integration and consulting decision support system.
System structure design
1. Functional structure design
This is a complex and professional geographic information system, which consists of external environment, flood control management support data warehouse, system technology management platform and application system. Among them, the application system consists of two functional modules: flood control business management function block and flood control decision support function block, which are respectively oriented to flood control business operators and flood control consulting decision users.
● The external environment includes computer network system (composed of special flood control network, water affairs bureau network and social public network) and communication infrastructure (composed of wired communication, mobile/wireless communication and satellite communication).
● Flood control management support data warehouse includes remote sensing image database, basic geographic database, socio-economic database and comprehensive flood control database.
● The technical management platform of the system is mainly aimed at technicians who maintain and develop the system operation. It consists of database management, system management, water conservancy application model interface management, interface management with network and communication, three-dimensional modeling tools, information collection and data conversion tools, corresponding to the technical support layer and management and maintenance layer of the system.
● The flood control business management function module is mainly oriented to daily flood control business processing, including: information service subsystem, real-time monitoring subsystem, daily affairs online office subsystem, remote centralized monitoring subsystem and flood control vehicle monitoring and dispatching subsystem.
● The flood control decision support function block is aimed at users with higher decision-making, mainly including flood forecasting, flood evolution simulation, flood dispatching, pipe network analysis, plan broadcasting, flood control deployment and disaster assessment.
2. Software architecture
Urban flood control management support system is a comprehensive application system, which not only meets the general flood control management information service, but also supports flood control consultation and decision-making. There are both simple data extraction and operation of water conservancy industry model; There are both applications of desktop computers and mobile devices. Therefore, in the design of architecture, it is necessary to ensure the relative independence between layers and the standardization of interfaces in order to enjoy the core service modules to the maximum extent.
Therefore, according to the (B/A/S) architecture design, it is generally divided into three layers, namely, presentation layer, application layer and data layer (Figure 4).
Fig. 4 Three-layer structure of urban flood control management support system
Browser is the man-machine interface of the system, running on Microsoft Windows IE. The main elements of man-machine interface are icons, buttons, tables, process lines and so on. For complex man-machine interface and man-machine interaction process, such as drawing hydrograph, drawing flood control command and dispatching scheme, thematic map, etc. Java applet is embedded in the web page, and the process of business layer and decision layer of the system is realized based on the browser.
The Web server is used to receive the request sent by the browser, send the request to the application server for processing, and then return the result to the browser.
The application server plays the role of handling scheduling and load balancing. All requests received by the web server are first sent to the application server for task assignment. According to different request types, the application server distributes the actual information reading, information processing and model calculation to different information service and model running servers for processing, and the application server realizes the main functions of the business layer and the technical layer.
Information service and model running server are the core processing parts of the system technical support layer. It is a logical concept, which can be physically represented as multiple servers or deployed on the same server. The model operations running on the logical server include: flood forecasting model, flood dispatching model, flood evolution model, GIS spatial analysis model and flood inundation loss evaluation model based on spatial superposition analysis model. Information service is mainly to extract real-time rainfall, engineering data, historical data and flood control business data from comprehensive database and publish them on the network. At the same time, GIS data is read from the spatial database, combined with comprehensive data to form a geographical map or thematic map, which is provided to the application server and then published to the browser through the application server.
The comprehensive database stores all non-spatial data, such as hydrological telemetry data, flood forecasting data, flood control dispatching decision support data, pumping station automation data, office automation data, basic water conservancy engineering data, flood control business data and social and economic data. The comprehensive database is stored in the relational database SQL Server. The upper server accesses the database through the database connection pool. Database connection pool is a buffer for storing database connection objects, which can enhance the speed and efficiency of database access, because it takes time to create database connections, and frequent creation and destruction of database connections will occupy a lot of computer resources. Spatial database is a database for storing digital topographic map, digital ground model DEM and three-dimensional model of river basin. The difference between spatial data and other data is that it contains both attribute data and geometric data, such as points, lines, surfaces, geometric bodies and so on. The traditional spatial data storage method is file-based, which has defects in multi-user concurrent access, data update and data access efficiency. In order to use mature relational database management systems (such as ORACLE and SQL SERVER), spatial database engine (SDE) technology stores spatial data in relational databases, and can use SQL statements to query, delete and modify data just like ordinary data.
XML is used for data exchange and communication between logical servers in the application layer. XML is an extensible markup language with good structure and easy parsing. By defining its structure and formulating various data interface standards, both parties can follow the same grammar, thus realizing interconnection.
Considering that flood control management is a complex system engineering, we should not only rely on modern advanced network technology, computer technology and GIS technology, but also rely on GPS, wireless communication, personal digital assistant (PDA) and other technologies to broaden information communication channels and improve emergency command ability. Therefore, the communication server and voice server are added in the application layer, and the support for mobile terminals such as mobile phones and PDA is added in the presentation layer.
The communication server is used to process the information requested or returned by mobile terminals such as mobile phones, PDA and GPS. , such as flood control site information, flood control command vehicle location, etc. These requests or returns are usually encoded according to a certain format, and the communication server decodes them and forwards them to the application server for processing. The communication server is also responsible for wirelessly sending various instructions or information from the command center to all mobile terminals. The communication between the communication server and the mobile terminal is carried out through the short message of GSM or the data service of GPRS.
The voice server is used to handle requests for information by telephone. It is realized by integrating voice card with computer and establishing call center.
GPS vehicle-mounted terminal is a vehicle-mounted device installed on flood control command and transport vehicles. It consists of GPS module, GSM/GPRS wireless communication module, GPS antenna and integrated processing module with single chip microcomputer. Users can report the exact location and other status information of vehicles in real time, such as traffic conditions, full load and no load, etc. The equipped LCD screen can also display the command and dispatch information of the command center. The application of GPS vehicle terminal can realize real-time monitoring and command and dispatch of flood control vehicles, so that commanders can master the flood control dynamics as much as possible.
(Chi Tianhe, Zhang Xin, Luo, Institute of Remote Sensing Application, Chinese Academy of Sciences; Hu Kai: Shenzhen Flood Control Facilities Management Office)
Brief introduction of the author
Zhang Xin: postdoctoral fellow, Institute of Remote Sensing Application, Chinese Academy of Sciences, mainly engaged in theoretical and technical research in digital city, e-government, regional major disaster prevention and mitigation information service system, digital ocean and other related fields. He has published more than 30 papers.