EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Open Access Nat. Hazards Earth Syst. Sci. Discuss.,Natural 1, 2859–2881, Hazards 2013 Natural Hazards www.nat-hazards-earth-syst-sci-discuss.net/1/2859/2013/and Earth System and Earth System doi:10.5194/nhessd-1-2859-2013 NHESSD © Author(s) 2013. CC Attribution 3.0 License.Sciences Sciences Discussions 1, 2859–2881, 2013 Open Access Open Access Atmospheric Atmospheric This discussion paper is/has been under review for the journal Natural Hazards and Earth Chemistry Chemistry Using VGI for 2012 System Sciences (NHESS). Please refer to the corresponding final paper in NHESS if available. and Physics and Physics flood mapping in Discussions Slovenia Open Access Open Access Atmospheric Atmospheric Measurement Measurement M. Triglav-Čekada and Using volunteeredTechniques geographicalTechniques D. Radovan Discussions Open Access information to map the November 2012Open Access Biogeosciences Biogeosciences Title Page Discussions floods in Slovenia Abstract Introduction Open Access M. Triglav-Čekada and D. Radovan Open Access Conclusions References Climate Climate Geodetic Institute of Slovenia, Ljubljana,of the Past Slovenia of the Past Tables Figures Discussions Received: 15 May 2013 – Accepted: 6 June 2013 – Published: 25 June 2013 Open Access Open Access J I Correspondence to: M. Triglav-EarthČekada System ([email protected]) Earth System Published by Copernicus PublicationsDynamics on behalf of the European GeosciencesDynamics Union. J I Discussions Back Close Open Access Geoscientific Geoscientific Open Access Full Screen / Esc Instrumentation Instrumentation Methods and Methods and Data Systems Data Systems Printer-friendly Version Discussions Open Access Open Access Interactive Discussion Geoscientific Geoscientific Model Development Model Development 2859 Discussions Open Access Open Access Hydrology and Hydrology and Earth System Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Open Access Solid Earth Solid Earth Discussions Open Access Open Access The Cryosphere The Cryosphere Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract NHESSD Volunteered geographical information represents a promising field in the monitoring and mapping of natural disasters. The contributors of volunteered geographical infor- 1, 2859–2881, 2013 mation have the advantage that they are at the location of the natural disaster at exactly 5 the time when the disaster happened. Therefore, they can provide the most complete Using VGI for 2012 account of the extent of the damage. This is not always possible when applying pho- flood mapping in togrammetric or remote-sensing methods, as prior to the data acquisition an order to Slovenia carry out the measurements has to be made. On 5 and 6 November 2012 almost half of Slovenia was badly affected by floods. The gathering of volunteered geograph- M. Triglav-Čekada and 10 ical information in the form of images and videos of these floods will be presented. D. Radovan Two strategies were used: (1) a public call for volunteered contributions and (2) a web search for useful images and their authors. The authorship of these images was ver- ified with every contributor, and with the help of the volunteered images 12 % of the Title Page most severely affected river sections were mapped. Altogether, 1195.3 ha of flooded Abstract Introduction 15 areas outside of the usual riverbeds along a total river length of 48 km were mapped. The results are compared with those from satellite mapping of the same floods. Conclusions References Tables Figures 1 Introduction J I Knowledge about the extent of natural disasters is important for disaster management; this is because natural disasters cannot be prevented, and mitigation of their impact J I 20 is the only option. Disaster management includes risk reduction by means of spatial Back Close planning, technical measures and an improvement of public awareness (Poser and Dransch, 2010). The public, on the other hand, can help to define the extent of natu- Full Screen / Esc ral disasters through volunteered geographical information (McDougall, 2012). In this article, using the Slovenian flood of November 2012 as an example, the flood-extent Printer-friendly Version 25 mapping resulting from volunteered geographical information is presented. Interactive Discussion 2860 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | The extent of floods can be measured by different remote-sensing methods, from aerial photogrammetry to high-resolution satellite data (e.g., Lane et al., 2003; Schu- NHESSD mann et al., 2011). Such missions have to be carried out within a maximum of a few 1, 2859–2881, 2013 days of the event, as the floods recede quickly. Unfortunately, in this period, bad 5 weather usually hinders the successful acquisition of optical satellite or aerial pho- togrammetric data. In addition, the limited spatial resolution of satellite data may hinder Using VGI for 2012 the detection of small flooded areas in vegetated, commercial or residential areas (Mc- flood mapping in Dougall and Temple-Watts, 2011). The order of the flood-data acquisition cannot be Slovenia completed during the time of the disaster: therefore, only some kind of post-maximum M. Triglav-Čekada and 10 extent of the natural disaster can be measured using traditional means. On the other hand, so-called volunteered geographical information can record a nat- D. Radovan ural disaster at the exact time of its maximum extent, as the contributors usually live in the vicinity and are affected by it. Additionally, this volunteered geographical informa- Title Page tion is not hindered by weather conditions. Volunteered geographical information, as 15 defined by Goodchild (2007), describes humans as sensors giving voluntarily temporal Abstract Introduction and spatial geographical information in the form of images, videos, sounds and text messages. Some data are already geolocated automatically, while others can be ge- Conclusions References olocated during the time of the data processing. In the case of floods the volunteered Tables Figures geographical information can help fill the gaps in the satellite imagery (Schnebele and 20 Cervone, 2013) or can be used as stand-alone information (Poser and Dransch, 2010; J I McDougall and Temple-Watts, 2012). The volunteered geographical information can also be used for assessing the extent of other natural disasters, for example, the New J I Zealand earthquake of 2011 and the Japanese tsunami of 2011 (McDougall, 2012). Back Close Almost every year, local heavy rain induces floods in Slovenia to a lesser or greater 25 extent. Due to the country’s diverse topography, which causes extensive climatic vari- Full Screen / Esc ability over short distances, these floods are mainly local. The floods tend to happen in late summer and autumn (Rusjan et al., 2009). However, the heavy rains between 4 Printer-friendly Version and 5 November 2012 caused extensive floods, affecting areas of all the major rivers covering the majority of the northern half of Slovenia on 5 and 6 November 2012. Be- Interactive Discussion 2861 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | tween 4 and 6 November up to 280 mm of rain fell on the mountain ranges in north-west Slovenia, up to 160 mm on the mountain ranges in north Slovenia, between 30 mm and NHESSD 100 mm in central Slovenia, and 20 mm to 50 mm on the southern part of Slovenia. 1, 2859–2881, 2013 Prior to this rainfall the soil was already heavily soaked because of the rain that fell one 5 week earlier. This caused the water level in the rivers to increase dramatically and the water to spill over in the form of floods (ARSO, 2012). Using VGI for 2012 This paper gathers the volunteered geographical information in the form of amateur flood mapping in images and uses them as the main source of data to assess the extent of the flood. In Slovenia Sect. 2 the study area and additional data used in the study are presented. The data M. Triglav-Čekada and 10 gathering and the methods are presented in Sect. 3. In Sect. 4 the share of the areas mapped with the volunteered images compared to the total extent of the flooding is D. Radovan derived. Additionally, the results of flood mapping from satellite images are compared to the flood mapping from the volunteered images. In Sect. 5 proposals are given for future Title Page actions. The volunteered geographical images used in this example have demonstrated 15 a great potential for detailed flood mapping. Abstract Introduction Conclusions References 2 Data Tables Figures 2.1 Study area J I On 5 and 6 November 2012 floods affected almost the whole northern half of Slovenia. The collaborative gathering of volunteered images was designed to cover as broad an J I 20 area as possible. The data gathering of the volunteered images and the methodology Back Close for the data acquisition will be described in detail in the next section. The total extent of the floods can be described with the most affected rivers, which are drawn in Fig. 1. Full Screen / Esc 2.2 Additional data – satellite mapping products Printer-friendly Version For the comparison of results gained with the volunteered image gathering, additional Interactive Discussion 25 satellite mapping products were used. These were already-interpreted flood maps from 2862 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | “GIO EMS Mapping products” showing flooded areas at general-overview topographic scales of 1 : 45 000 and 1 : 55 000, presented in Fig. 1 in a yellow colour. For some NHESSD smaller parts inside those areas detailed maps on a scale of 1 : 15 000 were also avail- 1, 2859–2881, 2013 able. The GIO EMS mapping products are based on satellite images and were pro- 5 duced in rush mode (EMS mapping portal, 2013).