Kamal Serrhini

Evaluating cartographic design in flood risk mapping

In order to mitigate flood hazards and to minimize associated losses, technical protection measures have been additionally and increasingly supplemented by non-technical mitigation, i.e. land-use planning activities. This is commonly done by creating maps which indicate such areas by different cartographic symbols, such as colour, size, shape and typography. Hazard and risk mapping is the accepted procedure when dealing with natural hazards and is therefore required in the European Member States in order to meet the demands of the European Flood Risk Directive. However, available information is sparse concerning the impact of such maps on different stakeholders, i.e. specialists in flood risk management, politicians and affected citizens. The lack of information stems from a traditional approach to map production which does not take into account specific end-user needs. In order to overcome this information shortage the current study used a circular approach such that feedback mechanisms originating from different perception patterns of the end user would be considered. Different sets of small-scale as well as large-scale risk maps were presented to different groups of test persons in order to (1) study reading behaviour as well as understanding and (2) deduce the most attractive components that are essential for target-oriented communication of cartographic information. Therefore, the method of eye tracking was applied using a video-oculography technique. This resulted in a suggestion for a map template which fulfils the requirement to serve as an efficient communication tool for specialists and practitioners in hazard and risk mapping as well as for laypersons. Taking the results of this study will enable public authorities who are responsible for flood mitigation to (1) improve their flood risk maps, (2) enhance flood risk awareness and, therefore, (3) create more disaster-resilient communities.

Flood Risk and Flood hazard maps – Visualisation of hydrological risks

Hydrological models are an important basis of flood forecasting and early warning systems. They provide significant data on hydrological risks. In combination with other modelling techniques, such as hydrodynamic models, they can be used to assess the extent and impact of hydrological events. The new European Flood Directive forces all member states to evaluate flood risk on a catchment scale, to compile maps of flood hazard and flood risk for prone areas, and to inform on a local level about these risks. Flood hazard and flood risk maps are important tools to communicate flood risk to different target groups. They provide compiled information to relevant public bodies such as water management authorities, municipalities, or civil protection agencies, but also to the broader public. For almost each section of a river basin, run-off and water levels can be defined based on the likelihood of annual recurrence, using a combination of hydrological and hydrodynamic models, supplemented by an analysis of historical records and mappings. In combination with data related to the vulnerability of a region risk maps can be derived. The project RISKCATCH addressed these issues of hydrological risk and vulnerability assessment focusing on the flood risk management process. Flood hazard maps and flood risk maps were compiled for Austrian and German test sites taking into account existing national and international guidelines. These maps were evaluated by eye-tracking using experimental graphic semiology. Sets of small-scale as well as large-scale risk maps were presented to test persons in order to (1) study reading behaviour as well as understanding and (2) deduce the most attractive components that are essential for target-oriented risk communication. A cognitive survey asking for negative and positive aspects and complexity of each single map complemented the experimental graphic semiology. The results indicate how risk maps can be improved to fit the needs of different user groups. Recommendations were developed of how to provide stakeholder-oriented information on hydrological risks.

How evacuation maps work: comparison of stakeholders’ visual strategies

ABSTRACT In the event of a major flood, many stakeholders implement a time-limited evacuation of residents to minimize the impact on the population. In this situation, the map is an important tool to facilitate decision-making and displacement of people. Many stakeholders have their own missions and questions but have also different experiences that influence how they read a map. In order to produce the most effective maps, it is important to understand how they read the maps and what can complicate their use. From the analysis of fixations and reading strategies, we determine (1) whether the different categories of stakeholders involved in the evacuation have specific characteristics in their map reading and (2) what components of evacuation maps can obstruct the map reading.

Cartographic representation of soundscape: proposals and assessment

Environmental noise is a major concern for city dwellers, however, actual noise maps are not adapted to them. The work described here is developed in the context of the CartASUR project which specifically addresses these deficiencies of noise maps. CartASUR collected perceptual data in several places of Paris using a survey and aiming to define new urban soundscape indicators to offer the possibility of several interpretations depending on the users’ personal and cultural characteristics, and to show them on maps. In this chapter, the indicators sound pleasantness and global loudness are presented. Several cartographic proposals are made to portray indicators during one, two, or three periods (day, evening, night) on maps, and their characteristic features (symbol design, visual variables) are discussed. Cartographic proposals are assessed through a survey which addresses the understanding of cartographic symbols and global properties of maps. The survey concludes that map readers prefer to view complete (both sound pleasantness and global loudness) and precise (three measurement periods) information, even when the amount of information leads to complex maps, which are considered the most attractive and useful. Nevertheless, the survey shows that these complex maps are not well interpreted by a large part of map readers. Use of visual variables color and quantity is discussed and proposals are made to improve symbol understanding.