Flood Forecasting (FF)
Flood forecasting systems, producing real-time forecasts of river flows and levels, provide a cost-effective solution to many flood management problems. It has been designed to perform the calculations required to predict the variation in discharges and water levels in a river system as a result of catchment rainfall and inflow/outflow through boundaries in the river system. From the MIKE 11 –FF module, the hydrodynamic model HD and the rainfall-runoff model NAM are controlled. All necessary input data and runtime parameters can be specified from MIKE11-FF. The MIKE 11- FF module has a real time data management facility with direct access databases and user-designed data entry menus. It reduces to a minimum the time required for entering of real-time and forecast data and other needed information for the simulations. In the add-on module, MIKE 11 FF, flood-forecasting techniques are used to predict local flood levels and river discharges. The forecasts can be used to set up control strategies for reservoir operation, which will prevent or reduce flooding in the downstream reaches and avoid unnecessary waste of water resources. Moreover, the forecasts form the basis for the dissemination of warnings to local authorities and the public. The forecasts provide information on the time scale and the extent of the flood inundation expected locally. Consequently, flood-forecasting techniques constitute a viable and important tool within flood management.
Development of Flood Warning System
Methodology of development of warning system is summarized in the flow chart (Figure 1). Forecasted water levels have been imported to MIKE GIS to map flood inundation maps. These maps are intersected with land use/ settlement maps to delineate flood inundation areas using techniques involved in GIS.
MIKE 11 and GIS are successfully integrated in Arc View GIS environment for retrieving near-real time flood level information. The study illustrates that an effective warning system can release warning in advance say 72, 48 and 24 Hrs in advance. It can change the existing perspective of flood preparedness and mitigation substantially and render information for better decision making for saving lives of people.
Customised and Automated Evacuation System
Adequate flood warning is a crucial element in emergency management, and operations of all of the systems around flood forecasting that the flood forecasting actually deals with.
The Network Analyst was employed to calculate the best way to get from one location to another or the best way to visit several locations. We can specify the locations by pointing to places on the screen, by entering address, or by using point information. We can decide the order they are visited, or we can let Network Analyst find a visiting sequence for us.
Finding best route
Best Route means different alternate route in different situations. For example, while people are affected under disaster, they need to be rescued by any means. So the selection of the quickest route to the hospital or to the cyclone shelter is very important at that moment.
The network Analyst supports different objectives, such as traveling quickly, traveling by the shortest route, traveling by the most interesting route, or any other criteria we specify. WE need only to specify an appropriate cost field in our line theme’s feature table when solving the problem. We can also make a route according to our personal preferences by specifying locations to pass along the way. The cost field we use can be in any units of distance or travel time, such as minutes or hours if we are finding a route that minimizes travel time, or kilometers or miles if we are finding a route that minimizes travel distance.
Finding the Closest Facility
“Closest facility” refers to anything providing a certain type of service that is closest to a given location, known as event. When finding the closest facility, we can specify whether the direction of travel is from the event to the facility, or whether it’s from the facility to the event. Direction of travel can be an important distinction because traffic pattern, one-way streets, and prohibited turns may make a facility more remote in one direction than in another. Identifying the closest facilities is only part of the solution. We also need to know the best way to get to or from them. Whenever we solve a closest facility problem, the Network Analyst also finds the best routes to travel to or from the facilities.
Customisation
The model was customised to make it user friendly, interactive, using Arc view script Avenue and Dialog Designer. To customize Arc View for our own use, we have created default settings for each default type (View, Table, Chart, Layout, Script, Project) and also create new user interfaces.
The project window contains a scrolling list of types, which by default contains View, Table, Chart, Layout and Script. With Customise Types, we can remove some of these types, we can change their names, we can change the icon that appears in the scrolling list, and we can reorder the types (e.g., move Scripts before Views). We can also create new types. Through the project window, we can create “virtual” documents and organize our project in ways that make sense for our application.
The methodology and database has been customised in Arc View GIS for user friendly interface and easy implementation. Figure 2 shows the customised window of the Dynamic GIS based Flood Warning System.
References
- BPC, 1994, Bangladesh Population Census, 1994, Zila: Gaibandha: 1994, Bangladesh Bureau of Statistics
- EGIS, 1998, Microwave Remote Sensing Applications for Flood Monitoring. Environmental and GIS Support Project for Water Sector Planning, Dhaka.
- Sanders R. and Tabuchi S., October, 2000, Decision Support System for Flood Risk Analysis for River Thames, United Kingdom, Photogrammetric Engineering & Remote Sensing Journal, Vol. 66, No. 10
- Sirivilai K., 997, Application of Flood Plain Mapping and Risk Assessment by the Integration of Fused Multisensor Remote Sensing Derived information within a GIS, AIT thesis No. SR – 97- 12, Bangkok, Thailand.
- Tawatchai, T., 1999, Use of Geographic Information Systems and Remote Sensing in Hydrological modeling. A Publication of the School of Civil Engineering, Asian Institute of technology, Vol. 1, No. 1.pp.7