Customized Visualization of Natural Hazards Assessment Results and Associated Uncertainties through Interactive Functionality

Article excerpt

Introduction

Natural disasters cause suffering through the harm of people and infrastructure as well as enormous economical damage. Natural hazard management aims at minimizing these impacts by the tasks of prevention, event management, and rebuilding (Bezzola and Hegg, 2008). Assessments of natural hazards form the basis for all management tasks and are therefore a crucial component of hazard management. This fact has become apparent during the last years and consequently funds for the advancement of hazard assessments as well as the enhancement of management strategies have been allocated (e.g. by the Swiss Government).

Cartographic representations have proved suitable for the communication of hazard assessment results which is reflected in the fact that the generation of hazard maps as basis for land-use-planning is standard procedure in many countries and in some places even regulated by law (e.g. Switzerland (1), Colorado (2), and many more).

Motivation

Recent analyses of past flood events (Bezzola and Hegg, 2008) showed that the requirements towards hazard maps have increased over the last years: not only spatial planners for whom these maps were designed work with these visual representations of natural hazard assessment results, but also many other specialists involved in different tasks of hazard management. Bezzola and Hegg (2008) therefore suggest that hazard assessments should not be performed for a particular application anymore but as a general basis for various future uses. Once these multifaceted results exist, they can be visualized for specific users according to their requirements. These visualizations, however, have to be generated following cartographic design principles in order to produce clear and well balanced maps that are effortlessly readable.

An additional issue which is often discussed in different hazard management phases and tasks is the question of uncertainty inherent to hazard assessment results. Many important decisions that can have severe consequences for third parties (e.g. initiation of evacuation, construction bans, etc.) are based on these results. Information about the accuracy of the presented assessment results is therefore very important. However, until now, most hazard maps pretended absolute certainty by solid borders of hazard zones even though experts agree that the definition of hazard zones is associated with uncertainy. Apart from the difficulties of quantifying existing uncertainties, this issue also poses a cartographic challenge: there are no guidelines about suitable methods for uncertainty visualization in natural hazard maps and most existing recommendations are only of theoretical nature (Pang 2008).

Overview and References to Related Work

The Internet has evolved to one of the most relevant media to publish cartographic information, as it facilitates greater access to spatial information, increased levels of interactivity with maps, real-time locational information, and greater integration of multimedia content through pictures, sound, and video (Peterson, 2008). In recent years, web cartography shifted towards a distributed and service-oriented cartography, providing individual maps on-demand for specific purposes (Schnabel and Hurni, 2009). While early web maps were mostly raster-based and static, modern interactive applications allow for thematic as well as geographic navigation and offer visualization functionality to display available information according to the specific needs of the users. In addition, users can be guided through the map making process in order to avoid the violation of cartographic rules. Consequently, a web-based cartographic information system provides a well suited environment for the visualization and exploration of natural hazards assessment results as well as associated uncertainties.

Chesneau (2004) analyzed over two hundred hazard visualizations which were published in geographic journals and the Internet and observed that most maps are published in printed form; interactive or multimedia environments are rare. …