Layman Report. Project FloodScan

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1 Layman Report Project FloodScan LIFE 06 ENV/D/ Large Scale Adjustment of New Technology for Fast, Precise and Cost-efficient Hydraulic 2d-Modelling of Flood (Hazard) Areas by Combining Laser Scanning with Remote Sensing Data Task 9 D 11 Date: December 2009

2 1 Overview about the Project FloodScan The project FloodScan was supported by the EU-LIFE-Program. FloodScan is an interdisciplinary project dealing with remote sensing, hydraulic modelling and flood risk communication. The research was conducted in the state of Bavaria, Germany. Main target of the project is the large scale development of a new methodology for fast, precise and costefficient hydraulic 2d-modelling of flood (hazard) areas by combining laser scanning with remote sensing data. The results are visualized for the general public using innovative information tools. Project duration: July 2006 to December Floods in Bavaria The state of Bavaria repeatedly faces major, sometimes even catastrophic flood events. In the last twenty years, there had been several big floods in the catchment area of the river Main (1993, 1995, 2003 and 2006). In the South of Bavaria and in the catchment area of the Danube major flood events occurred in 1999 (Pentecost Flood 1999) and in August 2002 (Century Flood 2002). Experts distinguish between flash floods and river floods. Usually, heavy rainfalls and thunderstorms cause flash floods, especially in Alpine regions. Thunderstorms with heavy precipitation can also lead to local floods of small water bodies on plains. In 2007, the administrative district of Forchheim was heavily affected. In a thunderstorm 75 mm of rain and hail fell within one hour. This equals 10% of the annual rainfall in this area. In short time, small water bodies turned into rapid rivers. The drain system failed to cope with water. In the municipality of Baiersdorf alone, 1000 houses were flooded. The flood caused about 100 Million Euro in damage. River floods are mainly caused by intense and continuous rain. Because of the long lasting rainfalls, the soils are water-saturated. This leads to undiminished surface run-off that accumulates in the rivers and causes inundations. In summer these floods mainly occur when the soils are already saturated by previous precipitation. In winter the soils can absorb only little or no water because they are frozen or covered with snow. Rain and simultaneous snow melting triggered the Pentecost Flood 1999, which caused 346 Million Euro in damage. For more than 150 years, this hydraulic system has been influenced by human activity, including river regulations, reductions of flood plains, soil sealing and settlement. This has increased flood 2

3 hazards. Experts anticipate a further increase in frequency and intensity of floods in future due to climate change. Therefore, precautionary measures constitute an important part of flood risk management, along with structural protection measures and the improvement of retention facilities. In Bavaria, flood risk management includes: Calculation and designation of flood plains and water-influenced areas. Designation of flood plains in land use plans and land development plans Improvement of flood forecasting and warning systems, for example by using the flood information system (Hochwassernachrichtendienst, HND) Reduction of building vulnerabilities and distribution of information about flood risks and individual precaution measures among the population. 3 The FloodScan Project and Flood Precaution The FloodScan project offers best-practice procedures for flood precaution as an important part of flood risk management in three different areas: basic data, hydraulic modelling and informing of the public. The project contributed to the implementation of the EU Floods Directive by developing flood hazard maps that serve as a basis for the development of flood risk maps and the flood risk management plans. FloodScan s main task is the optimization of the hydraulic modelling of flood hazards. Using data derived from airborne laser scanning and improved procedures for two-dimensional hydraulic modelling, the Bavarian water authorities will be able to identify flood prone areas and to create flood hazard maps more cost-efficiently. Flood hazard maps play a central role in flood precaution and can reduce flood damages, sinde they provide a basis for local administrations, planning agencies, emergency managers and information activities for the public. 3

4 4 The Project FloodScan as River The FloodScan project can be compared to the course of the river (Fig. 1). A typical river, like the Danube or the Isar, has diverse small tributaries that bring together their water in the middle reaches of the main river. The main river becomes larger and broader; further tributaries join it. In the lower reaches the river broadens to form a delta and finally flows into the sea. In the next sections, we present our project following these lines. digital terrain model of river channel digital terrain model of foreland land cover hydrology hydraulic modelling information tools information tools Figure 1: FloodScan as River 4

5 4.1 The Tributaries of the River FloodScan Basic data collection constitutes the tributaries of the FloodScan project river. As the first step, FloodScan improves the acquisition and preparation of these data. As innovative concept for the collection and provision of nation-wide digital terrain data, FloodScan uses data derived from airborne laser scanning and these data are further processed to digital terrain models that precisely represent the real terrain. The newest models offer one measuring point per square meter (1m grid). Figure 2 demonstrates the procedure of laser scanning and the resulting digital terrain model. The amount of data is very large, although it has been reduced when creating the terrain models. It is still far too large for the hydraulic modelling. Therefore, it is necessary to further reduce the amount of data. This is done by the automatic software Laser_AS-2d, which was further developed and adjusted in FloodScan. This software reduces the amount of Figure 2: Airborne Laser Scanning, Digital Tardata by 95%, especially in plane areas. Important rain Model terrain structures that have influence on the flow characteristics of floods are kept in the model, only in unimportant plane areas, many measuring points are deleted by the software. Beside this digital terrain model of the foreland, a digital model of the river channel is created. For this, cross profiles of the river are measured with terrestrial surveying and combined in a computer. The two digital models are merged together to one. Figure 3 shows these phases of the calculation of a model for a river channel. To calculate how fast the water can spread in the flood plains or to which extent the water is retained during a flood, it is necessary to classify the land cover. Different Figure 3: Digital Terrain Model of River Channel land use parameters (settlements, fields, forests, streets etc.) affect the course of a flood and therefore have to be taken into account. FloodScan has developed an automatic procedure to generate this information on land use from existing map data (ATKIS). Of course, hydrological basic data are also important for a precise simulation of flood hazards. Here, discharges for different flood scenarios are calculated by the water authorities for every 5

6 river in Bavaria. When dealing with a big river, the flood characteristics of every tributary have to be taken into consideration. 4.2 The Middle Reaches of the River FloodScan The mentioned data form the tributaries that flow together into the middle reaches of the project river FloodScan, i.e. into the so-called hydraulic twodimensional modelling of flood hazards and into the simulation of different flood scenarios (Fig. 4). The digital model that consists of the digital terrain model of the foreland and the digital model of the river channel serve as basis for the hydraulic modelling. In FloodScan the procedures have been improved and fastened. For the modelling, the software Hydro_AS-2d has been used. Results are flood plains, inundation heights and flow velocities for flood events with different occurrence probabilities. These results are further elaborated to flood hazard maps. Figure 4: Hydraulic two-dimensional Modelling 6

7 4.3 The Lower Reaches and the Delta of the River FloodScan In the lower reaches and the delta of the FloodScan project river, the dissemination of the project results and the information of the population at risk of flooding are the most important tasks. For this, the information derived from hydraulic modelling can be illustrated in flood hazard maps. Moreover, the extension of a flood can be visualized as a film sequence to be showed in public information events. Beside the printed version, the flood hazard maps are published in the public web mapping service, the information service flood hazard areas in Bavaria (IÜG-Informationsdienst Überschwemmungsgefährdete Gebiet in Bayern; Other innovative information tools, including flood information tables or the touring exhibition Flood Phone Booth (Fig. 5), are designed to inform the population about flood hazards. These risk communication measures are evaluated through the survey among the inhabitants of flood prone areas and through online-surveys among the users of the web mapping service. Main evaluation aspects are effectiveness, readability, usability, visualisation and design. Abbildung 5: Hochwasserinformations-Telefonzelle Figure 5: Flood Phone Booth 7

8 4.4 The Discharge of FloodScan into Flood Hazard Maps Every future-oriented flood protection conception should include the elaboration of flood hazard maps (LAWA 2004, 15). In 2005 this recommendation was included in the amendment of the Wasserhaushaltsgesetz (WHG, German Water Law) and thus received a legal status. Since the implementation of the EU Floods Directive of 2007 the creation of flood hazard maps has been required from all EU member-states. The responsible water authorities have to elaborate flood hazard maps for all Figure 6: Best Practice Flood Hazard Map for Würzburg water bodies with significant flood risks by The maps should demonstrate flood hazards for frequent, medium and seldom flood events. Flood hazard maps contain information about the spatial extent of flood scenarios with different occurrence probabilities (frequent, medium, seldom floods according to the EU Floods Directive) and about the extent of floods if the technical protection measures fail. Additionally, they contain inundation heights, flow velocities and information on the location and function of structural protection measures (Fig. 6). Using these maps measures should Figure 7: New Web Mapping Service: Flood Hazard Areas in Bavaria be developed to reduce flood risks. Flood hazard maps are an essential working document for emergency management and can support the municipal planning agencies in flood adjusted spatial planning activities. Moreover they provide information for the public for example via internet in web mapping services like the information service flood hazard areas in Bavaria (IÜG-Informationsdienst Überschwemmungsgefährdete Gebiete in Bayern; fig. 7). 8

9 For risk communication to the general public, it is important to keep the maps easy to understand with a readable legend and detailed but easily understandable explanations. Technical terminology like the 100-year flood (HQ100) have to be avoided. Blue colours should be used for the illustration of water depths or flooded areas because of the association of the colour blue with water. Real pictures of local flood events or flood related symbols like gauge boards can help to attract more attention to flood information. In the standard version, these recommendations can only be realised to some extent. The new Bavarian web mapping service developed within FloodScan meets these recommendations in its entirely. Users have the possibility to inform themselves about flood hazards of their living community or their property in an attractive and clearly arranged service. Using the direct link to the Bavarian flood information service they can get information about the current water levels and current flood alarm levels of all Bavarian rivers. 6. Environmental Effects and Future Benefits of the Project Results For Bavarian environment and population, the project results generated in FloodScan are of great importance. By simulating different flood scenarios flood risk management, especially flood precaution, can be improved. For example, it can now provide important flood information to municipalities, to emergency managers, to spatial planners and to the population in areas at risk of flooding. Experiences stemming from major flood events at the river Rhine in 1993 and 1995 demonstrate the enormous relevance of adequate risk awareness. The information gained through FloodScan project supports this view. Even though the water levels in 1995 were mostly higher than those in 1993, the damages in 1995 were about fifty percent lower because the affected inhabitants knew how to protect themselves and their property. The environment is also protected by improved flood precaution because flood hazard maps help to protect environmental and cultural assets. The maps can help to identify potentially polluting factories or industrial sites and contaminated sites in the areas at risk of flooding. These sites can be especially protected in case of emergency. 9

10 Contact All the relevant information about the FloodScan project and the project results can be found on the FloodScan-Webpage: Project Partners, Contact Information and Responsibilities within FloodScan Contact Information In FloodScan responsible for: Address Contact Lead Partner Bayerisches Landesamt für Umwelt Bavarian Environment Agency Bürgermeister-Ulrich-Str. 160 D Augsburg Dr. Dieter Rieger, (project leader) Project management Hydraulic modelling Classification of land cover Flood hazard maps Implementation of EU Floods Directive Creation of WMS Transferability of Flood- Scan methodology and project results Address Contact Landesamt für Vermessung und Geoinformation Bayern Bavarian Agency for Surveying and Geographic Information Alexandrastr. 4 D München Dr. Erwin Kistler Erwin.Kistler@lvg.bayern.de Airborne laser scanning Digital terrain models (DTM) Web-Mapping, Development of new Web Mapping Service Transferability of Flood- Scan methodology and project results Address Contact Technische Universität München, Lehrstuhl für Wald- und Umweltpolitik Chair of Forest and Environmental Policy Hans-Carl-von-Carlowitz-Platz 2 D Freising Prof. Dr. Michael Suda sekretariat@wup.wi.tum.de Dissemination and Contacts Evaluation and implementation of information tools in flood risk communication Communication with experts, media representatives and general public Transferability of Flood- Scan methodology and project results 10