Avalanche Situation in Turkey and Back-Calculation of Selected Events

Home , Bayburt, Bayburt Province, Trabzon Province, Zigana Pass

icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Open Access Nat. Hazards Earth Syst. Sci. Discuss., 2, 581–611, 2014 Natural Hazards www.nat-hazards-earth-syst-sci-discuss.net/2/581/2014/ and Earth System doi:10.5194/nhessd-2-581-2014 NHESSD © Author(s) 2014. CC Attribution 3.0 License. Sciences Discussions 2, 581–611, 2014

This discussion paper is/has been under review for the journal Natural Hazards and Earth Avalanche situation System Sciences (NHESS). Please refer to the corresponding ﬁnal paper in NHESS if available. in Turkey and back-calculation of Avalanche situation in Turkey and selected events back-calculation of selected events A. Aydın et al.

A. Aydın1, Y. Bühler2, M. Christen2, and I. Gürer3 Title Page 1Düzce University Faculty of Forestry, Konuralp Campus, 81620 Düzce, Turkey Abstract Introduction 2WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260 Davos Dorf, Switzerland Conclusions References 3Professor Emeritus, Gazi University Faculty of Engineering Civil Engineering Department, Maltepe 06570 Ankara, Turkey Tables Figures

Received: 24 December 2013 – Accepted: 8 January 2014 – Published: 21 January 2014 J I Correspondence to: A. Aydın ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. J I Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

581 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Abstract NHESSD In Turkey, an average of 24 people dies in snow avalanches every year, mainly in the eastern part of Anatolia and in the eastern Black Sea Region where high mountain 2, 581–611, 2014 ranges are close to the sea. The proportion of people killed in buildings is very high 5 (87 %), especially in comparison to other European and American countries. In this Avalanche situation paper we discuss avalanche occurrence, the climatic situation and historical avalanche in Turkey and events in Turkey; in addition, we identify bottlenecks and suggest solutions to tackle back-calculation of avalanche problems. Furthermore, we have applied the numerical avalanche simula- selected events tion software RAMMS combined with a Digital Elevation Model (DEM)-based potential 10 release zone identiﬁcation algorithm to analyze the catastrophic avalanche events in A. Aydın et al. the villages of Üzengili (Bayburt province) in 1993 and Yaylaönü (Trabzon province) in 1981. The results demonstrate the value of such an approach for regions with poor avalanche databases, enabling the calculation of diﬀerent scenarios and the estimation Title Page

of run-out distances, ﬂow velocities, impact pressure and ﬂow height. Abstract Introduction

Conclusions References 15 1 Introduction Tables Figures Mountain ranges can provide valuable resources such as minerals, recreational ser-

vices, wood for fuel and building material, and special agricultural products (Kräuchi J I et al., 2000). They are also an important source of water (Viviroli et al., 2007). How- ever, mountain environments, due to their harsh topography and climatic conditions, J I

20 are subject to natural hazards such as landslides, debris flows, rockfalls, flash floods Back Close and snow avalanches. Mountain areas occupy about one-fourth of the total land surface on Earth and are home to about one-tenth of all human beings (Ives et al., 1997; Price Full Screen / Esc and Butt, 2000). Seventy-eight percent of Turkey’s land surface consists of mountains, with 33.4 million people (about 47 % of the country’s total population) living in these Printer-friendly Version 25 regions (EEA, 2010). Interactive Discussion

582 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Turkey in general is comprised of two peninsulas, Thrace and Anatolia, with a 2-D- area of 769 471 km2, excluding lakes (Elibüyük and Yılmaz, 2010). This present land- NHESSD form was created by the convergence of Tethys sea sediments located among the 2, 581–611, 2014 African, Eurasian and Arabian plates. Thus, Alpine orogeny began with this conver- 5 gence and has continued up to present day (Bozkurt, 2001). Therefore, Turkey has been tectonically active, and this has directly affected the character of its landforms Avalanche situation and determined its aspect, slope and elevation features. Mountain ranges run in a west- in Turkey and east direction, parallel to the Black Sea in the north and to the Mediterranean Sea in back-calculation of the south. Comparatively high mountains (e.g. the Ağrı Mountain at 5165 m and the selected events 10 Reşko summit of Cilo Mountain at 4168 m) and plains (e.g. the Doğu Beyazıt plateau at 2000 m and the Erzurum plateau at 1900 m) exist at the eastern part of the Ana- A. Aydın et al. tolian peninsula (Fig. 1). According to a recent study (Elibüyük and Yılmaz, 2010) the mean altitude of Turkey is 1141 ma.s.l., more than three times higher that of Europe Title Page (300 ma.s.l.), with a mean slope angle of 10◦. Altitudes higher than 1500 m with slopes ◦ 15 greater than 27 cover 5.1 % of the total area. These values dramatically increase in Abstract Introduction the eastern Black Sea Region, which has been identified as a hot-spot for avalanches. The average altitude and average slope of the eastern Black Sea area are 1662 ma.s.l. Conclusions References ◦ and 19 , respectively. The elevation of 66 % of the total land surface is higher than Tables Figures 1500 ma.s.l. and 22.6 % of all the slopes are steeper than 27◦ (Elibüyük and Yılmaz, ◦ 20 2010). Altitudes higher than 1500 m with slopes greater than 27 cover 12 % of the total J I eastern Black Sea Region (Erkan Yılmaz, 2012 personal communication, see Fig. 1). Even though avalanches are a serious issue in Turkey, the management of snow J I avalanches has not yet attracted the necessary attention. According to a new regu- Back Close lation, the office of “Mountainous Areas Management (MAM)”, organized under the 25 Turkish Forest Service, was established in 2011. This new office is mainly responsible Full Screen / Esc for the prevention of floods, snow avalanches and landslides, and for preparing hazard and risk maps. Before the establishment of this office, the Avalanche Team (AT) of the Printer-friendly Version General Directorate of Disaster Affairs (GDDA) was responsible for this task. The AT was established after the destructive 1992/1993 avalanche cycle in Turkey and had Interactive Discussion

583 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion undertaken various national and international projects (Gürer, 1998). Because of the recent reorganization, this team was abolished and all staff members were transferred NHESSD to various other departments. This discontinuity has been a big drawback to setting 2, 581–611, 2014 up an institutional memory and years of accumulated experience have been lost. Due 5 to the vagueness of the duties and responsibilities of the MAM, no avalanche events have been recorded since the AT was abolished in 2009. The MAM office is located Avalanche situation in central Ankara and as of yet has no branch offices in local avalanche-prone ar- in Turkey and eas. When avalanches occur, there is at present no one responsible for recording and back-calculation of documenting the events, drawing outlines or making necessary measurements and selected events 10 analyses. Therefore, only a few recorded events are available, and there is no updated avalanche database in place today in Turkey. A. Aydın et al. Snow and avalanche mitigation profits substantially from research and development (R&D) organizations such as the WSL Institute for Snow and Avalanche Research Title Page SLF in Switzerland and the National Research Institute of Science and Technology for 15 Environment and Agriculture (IRSTEA, formerly CEMAGREF) in France. Continuity in Abstract Introduction research, determining the needs and gaps in research and practice, and increasing the quality of practical measures are some of the main aims of such institutions. In Turkey Conclusions References

there are no such research institutes, resulting in a lack of support for practitioners and Tables Figures capacity building in the country. 20 Even though the MAM is responsible for the hazard and risk mapping of natural J I hazards in Turkey, no guidelines or regulations exist to define the process of hazard and risk mapping; therefore, there are no restrictions on land use. As a result, build- J I ings, tourism facilities and traffic infrastructures are still being constructed in high-risk Back Close avalanche zones in Turkey. 25 In Turkey weather stations are operated by the State Meteorological Office (SMO). Full Screen / Esc All stations are located in city centers, which do not represent the high mountain ranges or places far from the cities where the avalanches occur. Furthermore, the total amount Printer-friendly Version of snow and rainfall precipitation as measured by the gauges is not differentiated. The Interactive Discussion

584 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion quality and scarcity of this meteorological data make them nearly meritless for analyz- ing avalanche events. NHESSD The aim of present paper is to describe the meteorological and avalanche situation 2, 581–611, 2014 in Turkey and to assess the applicability of a dynamic avalanche simulation model 5 (RAMMS) to back-calculate two well documented events. Avalanche situation in Turkey and 2 Climatic situation back-calculation of selected events In winter, Turkey is usually under the eﬀect of polar air masses, classiﬁed as maritime polar (mP) and continental polar (cP). Maritime polar air masses originate in the At- A. Aydın et al. lantic Ocean and pass over Europe from NW to SE (Fig. 2). They bring rainfall to the 10 Black Sea coast and snow to the inland region. Continental polar air masses originate in Siberia and are very cold and dry. When they pass over the Black Sea, they become Title Page moister and can cause orographic rainfall in the Black Sea coastal zone. When cP air masses reach the Mediterranean region, they get warmer and gain moisture, resulting Abstract Introduction

in thunderstorms. The Mediterranean and Black Sea mountain ranges run parallel to Conclusions References 15 the coasts. This topography causes significant differences in climate from one region to another. While coastal areas have a milder climate, the high mountain hinterlands of the Tables Figures coasts receive high amounts (2 to 3 m) of snowfall (Gürer and Naaim, 1993), and the inland Anatolian plateau experiences cold winters with limited precipitation e.g. 443 mm J I in Bayburt and 407.5 mm in Erzurum (Sensoy, 2004; Akçar and Schlüchter, 2005; Bek- J I 20 ereci et al., 2010). The orographic effects in both the Taurus and Black Sea mountains are dominant. For instance, in the eastern Black Sea Region, rainfall sharply decreases Back Close from coastal Rize, with a mean annual precipitation of 2200 mm, to the inland eastern Anatolian city of Erzurum, 130 km to the south, with mean annual precipitation of Full Screen / Esc 407.5 mm. Both cities are situated north of the Mediterranean climate boundary (Akçar Printer-friendly Version 25 and Schlüchter, 2005).

Interactive Discussion

585 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 3 Avalanche history NHESSD Historically, avalanches have occurred mainly in the eastern Black Sea Region, in eastern Anatolia, in the mountainous part of the south-eastern region of Anatolia, and last, 2, 581–611, 2014 but not least, in high and/or steep-sloped mountainous areas in the rest of the coun- 5 try (Fig. 3). Avalanche fatalities are high in Turkey, with an average of 24 lives lost per Avalanche situation year. Between 1951 and 2006, 676 avalanches were recorded in the Turkish avalanche in Turkey and archives, with a total of 1325 fatalities and 365 injured (GDDA, 2009). Most of these back-calculation of accidents took place in the eastern and south-eastern parts of the Anatolian penin- selected events sula (Fig. 3). Out of the 1325 deaths, 120 (9 %) were soldiers, 27 (2 %) were hunters, 10 18 (1.4 %) were skiers and climbers, 12 (0.9 %) were buried in cars on highways, one A. Aydın et al. (0.08 %) was a worker; the remaining 1147 (86.6 %) were local inhabitants trapped in their houses. About one-third of all recorded avalanches occurred in villages in the Trabzon, Rize and Bayburt provinces of the eastern Black Sea Region of Turkey (see Title Page

Fig. 1). During field visits to the eastern Anatolian and eastern Black Sea Regions of Abstract Introduction 15 Turkey, and after interviewing local people, we realized that the numbers in the archives seem to be significantly lower than the real numbers in terms of both, casualties and Conclusions References avalanche occurrences. Avalanche statistics demonstrate that avalanches in Turkey Tables Figures mainly affect settlements. In contrast, in the European Alps and in North America, most casualties result from winter sport activities (Schweizer and Lütschg, 2001; Zweifel J I 20 et al., 2012; Atkins, 2010). In recent years winter tourism has also gained importance

in Turkey, and the casualties have been increasing accordingly. As an example, on 25 J I January 2009, an avalanche in Zigana pass in Trabzon Province in Turkey’s eastern Black Sea Region buried 17 mountaineers, 10 of whom lost their lives. Similarly, on 11 Back Close

February 2006, 14 mountaineers were buried by an avalanche at Demirkazik summit in Full Screen / Esc 25 the Aladağlar Mountains of the Central Anatolian Region with four fatalities. During very extreme winter conditions, avalanches can occur at new locations where no avalanches Printer-friendly Version have been observed before. On 25 and 30 December 1992, in two events in the Kas- tamonu province of Western Black Sea Region of Turkey, 13 people were killed, two Interactive Discussion

586 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion injured and 17 houses damaged (Gürer et al., 1995). The altitude of the starting zone of one of these avalanches (Kayaarkası avalanche) was located as low as approximately NHESSD 900 ma.s.l. (Köse et al., 2010). Due to scarcity of avalanche data and the unavailabil- 2, 581–611, 2014 ity of an avalanche database in Turkey, we selected only the two best documented 5 and studied avalanche events, in order to back-calculate them with avalanche dynamic simulation model of RAMMS. Thus, the 1993 Üzengili (Bayburt Province) avalanche, Avalanche situation documented in several publications (Gürer and Naaim, 1993; Gürer et al., 1993), and in Turkey and the 1981 Yaylaönü (Trabzon Province) avalanche, where data was collected in the ﬁeld back-calculation of and aﬀected people interviewed by two of the authors, were selected for this study. selected events 10 Furthermore, these cases are located in the Bayburt–Rize–Trabzon triangle, a site ac- counting for one-third of all recorded avalanches in Turkey. A. Aydın et al.

4 Study area Title Page

This study was conducted in two diﬀerent survey areas (Üzengili and Yaylaönü) in or- Abstract Introduction

der to back-calculate the observed and documented avalanche events. Üzengili village Conclusions References ◦ 0 00 ◦ 0 00 15 is located at 40 23 00 E–40 29 30 N and is 41 km north of the Bayburt city center (Fig. 1). The village is located in the lee direction of the Soğanlı Mountains in the east- Tables Figures ern Black Sea Region of Turkey. The altitude of the village is 1950 ma.s.l. and it is in ◦ 0 00 a downstream area of bowl-shaped slopes. Yaylaönü village is located at 40 18 00 E– J I 40◦3501500 N and 105 km south-east of the Trabzon city center (Fig. 1). The village is J I 20 located in the northern part of the Soğanlı Mountains in the eastern Black Sea Region of Turkey at an altitude of 1700–1900 ma.s.l., at the edge of the central section of an Back Close avalanche track. For this study, we generated DEM datasets from 10 m contour interval and 1 : 25000 Full Screen / Esc scaled topographical maps. We generated raster data of the study area with a grid Printer-friendly Version 25 resolution of 10 m as input for the numerical simulations with RAMMS. Reference information on the events was obtained by interviewing affected people and, consulting Interactive Discussion photographs, newspaper articles and archives of official institutions. 587 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 4.1 The 1993 Üzengili avalanche NHESSD The Üzengili avalanche path consists of an open bowl in the upper part, a channeled ◦ ◦ 2, 581–611, 2014 track and an open run-out zone with slopes of 7 to 10 (Fig. 6). Both, the release and the run-out zones were sparsely vegetated with small bushes. The 1993 avalanche 5 stopped about 500 m before the bottom of the valley. A brief description of the Üzengili Avalanche situation avalanche and information on deposition height (at the center of the debris about 8– in Turkey and 10 m) can be found in Gürer and Naaim (1993). A sketch (Fig. 9) by the GDDA de- back-calculation of scribing the location of damaged buildings and mosque were given and it is assumed selected events that this sketch shows the boundary of the avalanche. Information on building damage A. Aydın et al. 10 and a collection of observations from local people were taken from GDDA archives. All residential structures were constructed from bricks and wooden material. Only mosque was constructed of masonry. Release depth estimation was done based on Gürer and Naaim (1993) and villagers’ statements and finally we use 160 cm for the model. Title Page The avalanche mass started from the high part of the mountain on 18 January 1993 Abstract Introduction 15 at 7.30 a.m. and buried 85 houses, 72 of which were completely destroyed or transported to the far end of the run-out zone (Fig. 4). Fifty-nine people were killed and Conclusions References

21 injured. Prior to the avalanche release, new snow had fallen continuously for a pe- Tables Figures riod of three days, with heavy northern winds which brought 70 cm of fresh and dry snow; the air temperature had consistently remained at well below zero (Gürer and J I 20 Naaim, 1993). The villagers inferred that the first avalanche had come from the slope on the orographic left hand side (the release zone of this avalanche is visible for the J I villager), filling the channel with snow deposits. Just a few minutes later, a second avalanche came from the slope on the right hand side (this release zone is invisible Back Close for the villager) and flowed over the previously filled channel, destroying large parts of Full Screen / Esc 25 the village. People mentioned a past avalanche which had occurred around 1890, in

which 10 houses disappeared. Other than this information, no one living there could Printer-friendly Version remember any other avalanche. Interactive Discussion

588 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 4.2 The 1981 Yaylaönü avalanche NHESSD In total four avalanches were recorded in Yaylaönü village. The ﬁrst recorded avalanche occurred in 1850’s, a second in 1974, a third in 1981 and the last in 1993. The 1850’s 2, 581–611, 2014 event killed three people and destroyed three houses (constructed from bricks and 5 wooden material), whereas the 1981 avalanche destroyed three houses (constructed Avalanche situation from bricks and wooden material) and the roof of the village’s school building (con- in Turkey and structed of bricks) (Fig. 5). A Bowl shaped release area, a channeled track and a run- back-calculation of ◦ out zone with slope angles of 8–11 , characterize the Yaylaönü avalanche path. All selected events release zones were covered by grass vegetation with no bushes or large trees. The 10 1981 avalanche stopped around 2000 m after releasing, with a 6 to 7 m deposition A. Aydın et al. height. There is no written information documenting this event.

Title Page 5 Numerical avalanche simulation software RAMMS Abstract Introduction The numerical avalanche dynamics simulation software RAMMS was developed at the Conclusions References WSL Institute for Snow and Avalanche Research SLF as a tool for engineers to calcu- 15 late two-dimensional run out distances, flow velocities, flow heights, impact pressures, Tables Figures and flow paths of large-scale snow avalanches. It is a further development of the one-

dimensional avalanche simulation tool AVAL-1D (Christen et al., 2002).The simulations J I are based on the Voellmy–Salm friction model containing two parameters: the Coulomb friction µ and the velocity squared dependent turbulent friction ξ (Voellmy, 1955; Salm J I

20 et al., 1990). The model, calibrated with real-scale avalanche measurements from the Back Close Swiss SLF test-site Vallée de la Sionne, requires high-quality DEM (Bühler et al., 2011; Bühler et al., 2012) as well as defined release areas and release depths. It solves the Full Screen / Esc depth-averaged equations governing avalanche flow with accurate second-order numerical schemes (Christen et al., 2010a). When used by experienced hazard experts Printer-friendly Version 25 combined with information on past avalanche events and field observations, RAMMS enables the calculation of different hazard scenarios as well as the back-calculation of Interactive Discussion 589 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion specific events (Bartelt et al., 2012; Christen et al., 2010b; Bühler et al., 2009). The software is commercially available and is used by avalanche experts and engineer- NHESSD ing offices to plan hazard mitigation projects around the world. Currently, a module for 2, 581–611, 2014 snow avalanche and one for debris flow simulations are available; modules for shallow 5 landslides and rock falls are under development (http://ramms.slf.ch). Avalanche situation in Turkey and 6 DEM-based release zone identification back-calculation of selected events Release zones for the Üzengili case were determined using a Geographical Information Systems (GIS)-based digital elevation model DEM analysis. No snow-pack or meteo- A. Aydın et al. rological parameters are included in this analysis. Slope, planar curvature, roughness 10 and size are the main parameters which are derived from the DEM in this procedure (Bühler et al., 2013). It is a further expansion of the algorithm developed by Maggioni Title Page and Gruber (2003) and works with high spatial resolution DEM datasets (10 m resolution and better). In this study, a DEM resolution of 10 m, a slope range of 28–60◦ Abstract Introduction

a curvature threshold of 3 and a ruggedness threshold of 0.03 were used. After a final Conclusions References 15 plausibility check by an avalanche expert and a correction procedure the release zones were used as input for the numerical simulation software RAMMS. Such an approach Tables Figures has the potential to be used for large-scale hazard mapping (Gruber and Bartelt, 2007). We identified 10 potential release zones in the first step using the DEM-based al- J I gorithm, see Fig. 6. In the second step, we checked the release zones manually and J I 20 selected and corrected the polygons, based on expert knowledge. Strong winds from the north and 70 cm of freshly fallen snow (over 10–20 cm of old snow) had been ob- Back Close served by the villagers just before the event. The release zones were located significantly higher than the Üzengili village. Therefore, based on the Swiss Guidelines (Salm Full Screen / Esc et al., 1990), we used a snow depth of 160 cm and included 50 cm of wind accumulation Printer-friendly Version 25 to calculate the release depths. For Yaylaönü event all information was collected in the field by interviewing villagers Interactive Discussion and observers. During the avalanche, strong winds from the south and more than 24 h 590 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion of continuous snowfall (90 to 100 cm) were reported. Three main release zones were identified. Based on this information, the release depth was estimated to be around NHESSD 160 cm (Fig. 7). 2, 581–611, 2014

7 Results and discussion Avalanche situation in Turkey and 5 7.1 Applied scenarios back-calculation of In Üzengili, the avalanche occurred at 7.30 a.m. and according to villagers’ observa- selected events tions came from the left-hand side slope (in the ﬂow direction) and ﬁlled the track with A. Aydın et al. a deposit of snow. Just a few minutes later a second avalanche came from the slope on the right hand side, causing the damage, so we know that the two avalanches came

10 just one after another. In order to corroborate the villagers’ statements with numerical Title Page avalanche simulations, we used six different elaborated scenarios (Table 1). RAMMS allows DEM modifications, for example, updating the track with a previous avalanche Abstract Introduction deposit. For scenarios 2 to 6 we made the DEM adaptation after releasing zone num- Conclusions References ber 1. Then we released the other zones over the adapted DEM to see the effect of 15 filling the track by the first avalanche. We applied six different probable scenarios, but Tables Figures only scenario 3 was able to cause an event as big as had been observed; the results

of scenario 3 are presented in the following sections. J I At the Yaylaönü site, the avalanche occurred at 09.00 a.m., so the eyewitnesses were clearly able to identify the release zone. The 1981 avalanche originated from release J I

20 zone number 1, see Fig. 7. Release zone number 1 was leeward of the strong south Back Close to north winds and the snow had accumulated heavily. Release zones number 2 and 3 were located at the windward side and the wind caused the snow to drift from there to Full Screen / Esc behind the northern ridge. Thus, only the avalanche release zone number 1 scenario was applied; the results are reported in the following sections. Printer-friendly Version

Interactive Discussion

591 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 7.2 Friction parameters NHESSD In RAMMS friction parameters can be specified as constant (for the whole calculation domain) or variable. Constant values are recommended for a first attempt to quickly 2, 581–611, 2014 analyze the problem (Christen et al., 2010b). Variable friction parameters for the entire 5 calculation domain are automatically calculated using GIS-based terrain analysis for Avalanche situation different return periods and avalanche volume classes (RAMMS Manual, 2010). in Turkey and In RAMMS, the dry coulomb friction µ and the velocity dependent turbulent friction back-calculation of ξ depend on the avalanche volume, the return period and the terrain. We used values selected events based on the calibration with avalanche events within the SLF real scale test site Val- 10 lée de la Sionne, in Switzerland. Because both events can be considered as extreme A. Aydın et al. and the volumes have been large (> 60 000 m3) we have chosen corresponding friction values. The aim of this study was not to calibrate the friction parameters for Turkish avalanches. Thus, for both study areas constant values of µ and ξ were used for the Title Page −2 entire calculation domain. For the Üzengili avalanche site µ=0.19 and ξ = 2100 ms Abstract Introduction 15 were selected, respectively. Because we had a channeled avalanche track at the Yay- laönü avalanche site, the parameters were selected as µ = 0.24 and ξ = 1500 ms−2, as Conclusions References suggested in the Swiss Guidelines (Salm et al., 1990). The Swiss Guidelines were de- Tables Figures veloped for the analytical Voellmy–Salm model. These values were adapted for numerical simulation with AVAL-1D (Christen et al., 2002) and RAMMS. These adaptations J I 20 are based on the back calculation of numerous large scale avalanches in a dissertation

at SLF (Gruber et al., 1998; Gruber 1998, Gruber and Bartelt, 2007). The adapted µ J I and ξ values are listed in Bartelt et al. (2010). Back Close 7.3 Flow heights, velocities and impact pressures Full Screen / Esc Üzengili avalanche site Printer-friendly Version

25 At the Üzengili avalanche site, according to the statements of eyewitnesses, the deposition height was about 7–8 m. This value may have occurred in some places due to the Interactive Discussion 592 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion obstacle effect of buildings. When considering the comparably wide run-out zone, a deposition height of 3–5 m at the center part was thought to be reasonable. However, at NHESSD the eastern part of the deposition zone much less deposition height simulated which is 2, 581–611, 2014 higher in the real situation. Contrary, at the most down part of the deposition zone even 5 no deposition observed a little bit deposition simulated (Fig. 8). A sketch (Fig. 9) by the GDDA describing the location of damaged buildings by the avalanche is included and it Avalanche situation is assumed that this sketch shows the boundary of the avalanche. Since no detailed in- in Turkey and formation on flow velocity or impact pressure was available, the simulation result could back-calculation of not be verified. However, a pressure of 10–20 kPa has been estimated at the mosque selected events 10 by visual interpretation on photographs which shows structural damages (Fig. 4), and corresponds well with the simulated avalanche results (M. Schaer, personal commu- A. Aydın et al. nication, 2012, SLF). Flow velocity and impact pressure for the entire avalanche track are given in Fig. 8. Furthermore, the impact pressure forces calculated at the mosque Title Page location are shown in Fig. 10. Abstract Introduction 15 Yaylaönü avalanche site Conclusions References At the Yaylaönü avalanche site, the villagers’ statements about a deposition height of 6–7 m seemed to be realistic. Due to a narrow, channeled run-out zone, simula- Tables Figures tion results also showed deposition to be around 7 m at the deposition zone, which complies with the villagers’ statements (Fig. 11). In 1981 the avalanche damaged the J I 20 school building by breaking doors and windows and uplifting roof, but it was not com- J I pletely destroyed. Maybe the damages at the building were caused by a powder cloud. A pressure of dense part of avalanche less than 1–2 kPa could have been seen at the Back Close edge of the school building and seems to be acceptable. The simulation results sup- Full Screen / Esc port this argument. A sketch based on villagers’ statements drawing the outline of the 25 1981 avalanche (Fig. 7) corresponds to the outline of the modelled avalanche (compare Fig. 7 and Fig. 11). Impact pressure for the entire avalanche track are given in Printer-friendly Version Fig. 11; impact pressure forces calculated at the damaged school location are shown Interactive Discussion in Fig. 12. 593 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 8 Conclusions NHESSD Turkey is a fast developing country, with more than 78 % of its territory in mountainous areas. According to information from Ministry of Transportation, 15 700 km of new 2, 581–611, 2014 double-lane highways have been constructed over the last ten years and there are 5 plans to build another 15 000 km of new railway lines by the year 2023. Furthermore, Avalanche situation winter sport activities have been increasing in Turkey during the last decade. It can be in Turkey and inferred that the importance of avalanches as a major natural hazards in Turkey will back-calculation of increase substantially. selected events In Turkey, the proportion of avalanche fatalities who die in their homes is very high 10 (87 %) compared with European and North American countries; for example in Switzer- A. Aydın et al. land and in the United States less than 5 % of the people who die in avalanches are killed in their houses. This is the result of the long history of great efforts in avalanche research, hazard mapping and mitigation measures established in this regions. Title Page

Avalanche mitigation requires a multidisciplinary approach. Thus in Turkey, a multi- Abstract Introduction 15 disciplinary organizational structure which includes foresters, GIS experts, civil engineers and geographers at the central and local offices of avalanche-prone areas are Conclusions References needed to improve the situation. Legislation gaps must be filled in order to outline Tables Figures a concrete definition of organizational duties and responsibilities. Avalanche mitigation needs the support of a strong R&D department. Unfortunately, in Turkey not many sci- J I 20 entists or researchers are involved in avalanche studies. Establishing an independent

research institute would ensure success in meeting the needs of operational branches J I and in the training of research staff. Furthermore, it is necessary to obtain sufficient meteorological data reflecting high mountain conditions. This could be achieved by setting Back Close

up an organized alpine weather station network. Full Screen / Esc 25 The Üzengili (Bayburt) and Yaylaönü (Trabzon) avalanches were selected to test the feasibility of using RAMMS in such cases. Even without meteorological data and the Printer-friendly Version lack of exact release area information of the Üzengili avalanche, RAMMS produced realistic results. The DEM-based release generation is a big help but requires expert Interactive Discussion

594 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion knowledge; using the generated release zones directly as input of RAMMS can be deceptive and cause unrealistic results. NHESSD We used default friction values with little modification in the Üzengili avalanche sim- 2, 581–611, 2014 ulations, as recommended by the Gruber et al. (1998), Gruber (1998), Gruber and 5 Bartelt (2007) and Bartelt et al. (2012). For the Yaylaönü avalanche site, we used the parameters for channeled avalanches which are recommended by the RAMMS Manual Avalanche situation (Bartelt et al., 2010). Even though, RAMMS is calibrated for large scale avalanches in in Turkey and Switzerland. It is very important to see that this model works also well in a climatically back-calculation of completely different regions such as Turkey with realistic results for our cases. This in- selected events 10 dicates the robustness and reliability of the Voellmy–Salm approach for avalanche simulation to improve hazard mapping and hazard zonation where such simulations are A. Aydın et al. missing for other areas than for the European Alps. But users should be very careful in using and keep in mind some main limitation of dynamic models such as calibrating Title Page parameters, sensitivity analysis, problems originated from event documentation and so 15 on (Jamieson et al., 2008). Abstract Introduction Although villagers in Üzengili claimed that the second avalanche had come from the right hand side slope (in flow direction), simulation results did not agree with this Conclusions References

statement. We concluded that the second avalanche originated from release zones Tables Figures number 3–5 of the left hand side slope (see Fig. 6 and Table 1). 20 This study shows that based on the observations and estimations made in this pa- J I per we assume that RAMMS can be help for hazard mitigation planning. The impact forces predicted by RAMMS at the mosque (Üzengili avalanche) and the school loca- J I tion (Yaylaönü avalanche) are in good agreement with the observed situation. Although Back Close generalization is not recommended, using RAMMS with expert knowledge for sparsely- 25 documented events can yield valuable information. Many countries with alpine regions Full Screen / Esc exist, where no or very sparse historic avalanche information exists. It is interesting to read for them how the tools developed elsewhere can be applied and what limitations Printer-friendly Version and problems occur. Besides, Hazard mapping in remote regions is a demanding task. However to do nothing is not an option in many regions. The application of numerical Interactive Discussion

595 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion simulations can therefore be a big help by keeping in mind their limitations, necessity of good event documentation and expert opinions. This papers show how such a tool NHESSD can be applied. 2, 581–611, 2014

References Avalanche situation in Turkey and 5 Akçar, N. and Schlüchter, C.: Paleoglaciation in Anatolia: a schematic review and first results, Eiszeitalter und Gegenwart, 55, 102–121, 2005. back-calculation of Atkins, D.: Ten years of avalanche deaths in the USA, 1999/00 to 2008/09, International Snow selected events Science Workshop 2010, Proceedings, Lake Tahoe, CA, 768–775, 2010. Bartelt, P., Buehler, Y., Buser, O., Christen, M., and Meier, L.: Modeling mass-dependent flow A. Aydın et al. 10 regime transitions to predict the stopping and depositional behavior of snow avalanches, J. Geophys. Res.-Ea. Surf., 117, 1–28, 2012. Bartelt, P., Bühler, Y., Christen, M., Deubelbeiss, Y., Graf, C., and McArdell, B.: RAMMS User Title Page Manual: Avalanche, SLF, Davos, available at: http://ramms.slf.ch, 2010. Bekereci, A., Küçük, Ö., and Çamalan, G.: The Föhn effects in forest fires of air masses affect- Abstract Introduction 15 ing Turkey, 1st Meteorology Symposium, 27–28 May, Ankara, Presentations Book, 83–95, (Original in Turkish), 2010. Conclusions References Bozkurt, E.: Neotectonics of Turkey – a synthesis, Geodin. Acta, 14, 3–30, 2001. Tables Figures Bühler, Y., Hüni, A., Christen, M., Meister, R., and Kellenberger, T.: Automated detection and mapping of avalanche deposits using airborne optical remote sensing data, Cold Reg. Sci. 20 Technol., 57, 99–106, 2009. J I Bühler, Y., Christen, M., Kowalski, J., and Bartelt, P.: Sensitivity of snow avalanche simulations to digital elevation model quality and resolution, Ann. Glaciol., 52, 72–80, 2011. J I Bühler, Y., Marty, M., and Ginzler, C.: High resolution DEM generation in high-alpine terrain Back Close using airborne remote sensing techniques, Transaction in GIS, 26, 635–647, 2012. 25 Bühler, Y., Kumar, S., Veitinger, J., Christen, M., Stoffel, A., and Snehmani: Automated iden- Full Screen / Esc tification of potential snow avalanche release areas based on digital elevation models, Nat. Hazards Earth Syst. Sci., 13, 1321–1335, doi:10.5194/nhess-13-1321-2013, 2013. Christen, M., Bartelt, P., and Gruber, U.: AVAL-1D: An avalanche dynamics program for the Printer-friendly Version practice, INTERPRAEVENT 2002 in the Pacific Rim, 2, 715–725, 2002. Interactive Discussion

596 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Christen, M., Kowalski, J., and Bartelt, P.: RAMMS: Numerical simulation of dense snow avalanches in three-dimensional terrain, Cold Reg. Sci. Technol., 63, 1–14, 2010a. NHESSD Christen, M., Bartelt, P., and Kowalski, J.: Back calculation of the In den Arelen Avalanche with RAMMS: interpretation of model results, Ann. Glaciol., 51, 161–168, 2010b. 2, 581–611, 2014 5 EEA (European Environment Agency): Europe’s ecological backbone: recognizing the true value of our mountains. EEA Report No 6, Copenhagen, 2010. Elibüyük, M. and Yılmaz, E.: Altitude steps and slope groups of Turkey in comparison with Avalanche situation geographical regions and sub-regions, J. Geogr. Sci., 8, 27–55, 2010 (Original in Turkish). in Turkey and Gruber, U., Bartelt, P., and Haefner, H.: Avalanche hazard mapping using numerical Voellmy back-calculation of 10 ﬂuid models, In Hestnes, E., ed, Proceedings of the Anniversary Conference 25 yr of Snow selected events Avalanche Research, Voss, 12–16 May 1998, Norwegian Geotechnical Institute, Publication No 203, Oslo, 117–121, 1998. A. Aydın et al. Gruber, U.: Der Einsatz numerischer Simulationsmethoden in der Lawinengefahrenkartierung: Möglichkeiten und Grenzen, Ph.D., Geographisches Institut der Universitaet Zürich, 1998. 15 Gruber, U. and Bartelt, P.: Snow avalanche hazard modeling of large areas using shallow water Title Page numerical methods and GIS, Environ. Modell. Softw., 22, 1472–1481, 2007. Gürer, I. and Naaim, M.: The Avalanche accident at Bayburt, Üzengili Located in North-Eastern Abstract Introduction Anatolia Türkiye on 18 January 1993, 2nd Avalanche Dynamics Workshop, Innsbruck, Aus- tria, 1993. Conclusions References 20 Gürer, I., Tunçel, H., Yavaş, Ö. M., Erenbilge, T., and Sayın, A.: Snow avalanche incidents in North-Western Anatolia, Turkey during December 1992, Nat. Hazards, 11, 1–16, 1995. Tables Figures Gürer, I.: International cooperation for solving the avalanche problem in Turkey, Nat. Hazards, 18, 77–85, 1998. J I Gürer, I., Toprak, F., and Ercan, S.: The avalanche accidents at Soğanlı Mountain located in 25 North-Eastern Anatolia, Türkiye on 18 January 1993. Presented in 5th International Con- J I ference on Natural and Man-Made Hazards, HAZARDS-93, 29 August–3 September 1993, Quingdao, China, 1993. Back Close Ives, J. D., Messerli, B., and Spiess, E.: Mountains in the World: a Global Priority, Carnforth- Full Screen / Esc Parthenon, 1997. 30 Jamieson, B., Margreth, B., and Jones, A. Application and limitatitons of dynamic models for snow avalanche hazard mapping, Proceedings of the International Snow Science Workshop Printer-friendly Version 2008, Telluride, Colorado, US, 730–739, 2008. Interactive Discussion

597 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Köse, N., Aydın, A., Akkemik, Ü., Yurtseven, and Güner, H. T.: Using tree-ring signals and numerical model to identify the snow avalanche tracks in Kastamonu, Turkey, Nat. Hazards, NHESSD 54, 435–449, 2010. Kräuchi, N., Brang, P., and Schönenberger, W.: Forests of mountainous regions: gaps in knowl- 2, 581–611, 2014 5 edge and research needs, Forest Ecol. Manag., 132, 73–82, 2000. Maggioni, M. and Gruber, U.: The influence of topographic parameters on avalanche release Avalanche situation dimension and frequency, Cold Reg. Sci. Technol., 37, 407–419, 2003. Price, M. and Butt, N.: Forests in Sustainable Mountain Development, IUFRO Research Series in Turkey and No. 5, 2000. back-calculation of 10 Salm, B., Burkard, A., and Gubler, H.: Berechnung von Fliesslawinen: eine Anleitung für Prak- selected events tiker mit Beispielen, Mitteilung 47, Eidg. Institut für Schnee- und Lawinenforschung SLF Davos, 47, 1–37, 1990. A. Aydın et al. Schweizer, J. and Lütschg, M.: Characteristics of human-triggered avalanches, Cold Reg. Sci. Technol., 33, 147–162, 2001. 15 Sensoy, S.: The Mountains Influence On turkey Climate, Balwois Conference on Water Obser- Title Page vation and Information System for Decision Support, Ohrid, 25–29 May 2004. Viviroli, D., Dürr, H. H., Messerli, B., Meybeck, M., and Weingartner, R.: Mountains of the world, Abstract Introduction water towers for humanity: topology, mapping, and global significance, Water Resour. Res., 43, 1–13, 2007. Conclusions References 20 Voellmy, A.: Über die Zerstörungskraft von Lawinen, Schweizerische Bauzeitung, Sonderdruck Tables Figures aus dem 73. Jahrgang (12, 15, 17,19 und 37), 1–25, 1955. Zweifel, B., Techel, B., and Björk, C.: Who is involved in avalanche accidents, Proceedings of International Snow Science Workshop 2012, Anchorage, Alaska, 234–239, 2010. J I

J I

Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al. Table 1. Applied scenarios (See Fig. 6).

Scenarios Release Zones Remarks First Second Title Page

S1 – – All released individually Abstract Introduction S2 1 2–5 DEM adaptation procedures applied S3 1 3–5 DEM adaptation procedures applied Conclusions References S4 1–2 3–5 DEM adaptation procedures applied S5 1 6–7 DEM adaptation procedures applied Tables Figures S6 1 8–10 DEM adaptation procedures applied J I

J I

Back Close

Full Screen / Esc

Printer-friendly Version

Interactive Discussion

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Fig.Figure1. 1. Physical Physical map map of Turkey of Turkey showing showing the most the most important important mountain mountain ranges ranges and studyand study areas J I (upper right corner). areas (upper right corner). Back Close

Full Screen / Esc 1

Printer-friendly Version 2 Even though avalanches are a serious issue in Turkey, the management of snow avalanches Interactive Discussion 3 has not yet attracted the necessary attention. According to a new regulation, the office of 4 “Mountainous Areas Management (MAM)”, 600organized under the Turkish Forest Service, was 5 established in 2011. This new office is mainly responsible for the prevention of floods, snow 6 avalanches and landslides, and for preparing hazard and risk maps. Before the establishment 7 of this office, the Avalanche Team (AT) of the General Directorate of Disaster Affairs 8 (GDDA) was responsible for this task. The AT was established after the destructive 9 1992/1993 avalanche cycle in Turkey and had undertaken various national and international 10 projects (Gürer, 1998). Because of the recent reorganization, this team was abolished and all 11 staff members were transferred to various other departments. This discontinuity has been a 12 big drawback to setting up an institutional memory and years of accumulated experience have 13 been lost. Due to the vagueness of the duties and responsibilities of the MAM, no avalanche 14 events have been recorded since the AT was abolished in 2009. The MAM office is located in 15 central Ankara and as of yet has no branch offices in local avalanche-prone areas. When 16 avalanches occur, there is at present no one responsible for recording and documenting the 17 events, drawing outlines or making necessary measurements and analyses. Therefore, only a 18 few recorded events are available, and there is no updated avalanche database in place today 19 in Turkey. 20 1 in climate from one region to another. While coastal areas have a milder climate, the high 2 mountain hinterlands of the coasts receive high amounts (2 to 3 m) of snowfall (Gürer and 3 Naaim, 1993), and the inland Anatolian plateau experiences cold winters with limited 4 precipitation e.g. 443 mm in Bayburt and 407.5 mm in Erzurum (Sensoy, 2004; Akçar and 5 Schlüchter, 2005; Bekereci et al., 2010). The orographic effects in both the Taurus and Black 6 Sea mountains are dominant. For instance, in the Eastern Black Sea Region, rainfall sharply

7 decreases from coastal Rize, with a mean annual precipitation of 2200 mm | , Paper to Discussion the | Paper Discussion inland | Paper Discussion | Paper Discussion 8 eastern Anatolian city of Erzurum, 130 km to the south, with mean annual precipitation of NHESSD 9 407.5 mm. Both cities are situated north of the Mediterranean climate boundary (Akçar and 2, 581–611, 2014 10 Schlüchter, 2005).

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Fig.Figure 2. Air 2. masses Air masses aﬀecting affecting Turkey Turkey (Akçar (Akçar and and Schlüchter, Schlüchter, 2005). 2005) Full Screen / Esc

11 Printer-friendly Version 12 3 Avalanche history Interactive Discussion 13 Historically, avalanches have occurred mainly in the Eastern Black Sea Region, in eastern 14 Anatolia, in the mountainous part of the south601-eastern region of Anatolia, and last, but not 15 least, in high and/or steep-sloped mountainous areas in the rest of the country (Figure 3). 16 Avalanche fatalities are high in Turkey, with an average of 24 lives lost per year. Between 17 1951 and 2006, 676 avalanches were recorded in the Turkish avalanche archives, with a total 18 of 1325 fatalities and 365 injured (GDDA, 2009). Most of these accidents took place in the icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I Fig.Figure 3. Avalanche3. Avalanche record record map map of of Turkey Turkey (Yellow (Yellow color color refers refers avalanche avalanche observed observed cities cities and and red star refers recorded avalanche locations, Source: GDDA). J I red star refers recorded avalanche locations, Source: GDDA) Back Close

1 Full Screen / Esc

2 4 Study area Printer-friendly Version

3 This study was conducted in two different survey areas (Üzengili and Yaylaönü) in order to Interactive Discussion 4 back-calculate the observed and documented avalanche events. Üzengili village is located at 602 5 40⁰ 23' 00'' E-40⁰ 29' 30'' N and is 41 km north of the Bayburt city center (Figure 1). The 6 village is located in the lee direction of the Soğanlı Mountains in the Eastern Black Sea 7 Region of Turkey. The altitude of the village is 1950 m a.s.l. and it is in a downstream area of 8 bowl-shaped slopes. Yaylaönü village is located at 40⁰ 18' 00'' E-40⁰ 35' 15'' N and 105 km 9 south-east of the Trabzon city center (Figure 1). The village is located in the northern part of 10 the Soğanlı Mountains in the Eastern Black Sea Region of Turkey at an altitude of 1700-1900 11 m a.s.l., at the edge of the central section of an avalanche track.

12 For this study, we generated DEM datasets from 10 m contour interval and 1:25.000 scaled 13 topographical maps. We generated raster data of the study area with a grid resolution of 10 m 14 as input for the numerical simulations with RAMMS. Reference information on the events 15 was obtained by interviewing affected people and, consulting photographs, newspaper articles 16 and archives of official institutions.

17 4.1 The 1993 Üzengili avalanche

18 The Üzengili avalanche path consists of an open bowl in the upper part, a channeled track and 19 an open run-out zone with slopes of 7º to 10º (Figure 6). Both, the release and the run-out 1 zones were sparsely vegetated with small bushes. The 1993 avalanche stopped about 500 m 2 before the bottom of the valley. A brief description of the Üzengili avalanche and information 3 on deposition height (at the center of the debris about 8-10 m) can be found in Gürer and 4 Naaim (1993). A sketch (Figure 9) by the GDDA describing the location of damaged 5 buildings and mosque were given and it is assumed that this sketch shows the boundary of the 6 avalanche. Information on building damage and a collection of observations from local people 7 were taken from GDDA archives. All residential structures were constructed from bricks and 8 wooden material. Only mosque was constructed of masonry. Release depth estimation was 9 done based on Gürer and Naaim (1993) and villagers’ statements and finally we use 160 cm 10 for the model.

11 The avalanche mass started from the high part of the mountain on 18 January 1993 at 07:30 12 a.m. and buried 85 houses, 72 of which were completely destroyed or transported to the far 13 end of the run-out zone (Figure 4). Fifty-nine people were killed and 21 injured. Prior to the 14 avalanche release, new snow had fallen continuously for a period of three days, with heavy 15 northern winds which brought 70 cm of fresh and dry snow; the air temperature had 16 consistently remained at well below zero (Gürer and Naaim, 1993). The villagers inferred that 17 the first avalanche had come from the slope on the orographic left hand side (the release zone 18 of this avalanche is visible for the villager), filling the channel with snow deposits. Just a few 19 minutes later, a second avalanche came from the slope on the right hand side (this release 20 zone is invisible for the villager) and flowed over the previously filled channel, destroying 21 large parts of the village. People mentioned a past avalanche which had occurred around 22 1890, in which 10 houses disappeared. Other than this information, no one living there could icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 23 remember any other avalanche. NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

J I Back Close

Fig. 4. Destroyed mosque due to 1993 avalanche event in Üzengili village. Full Screen / Esc

Figure 4. Destroyed mosque due to 1993 avalanche event in Üzengili Printer-friendlyvillage Version

Interactive Discussion

603 1 4.2 The 1981 Yaylaönü avalanche

2 In total four avalanches were recorded in Yaylaönü village. The first recorded avalanche 3 occurred in 1850’s, a second in 1974, a third in 1981 and the last in 1993. The 1850’s event 4 killed three people and destroyed three houses (constructed from bricks and wooden material), 5 whereas the 1981 avalanche destroyed three houses (constructed from bricks and wooden 6 material) and the roof of the village’s school building (constructed of bricks) (Figure 5). A 7 Bowl shaped release area, a channeled track and a run-out zone with slope angles of 8º -11º, 8 characterize the Yaylaönü avalanche path. All release zones were covered by grass vegetation 9 with no bushes or large trees. The 1981 avalanche stopped around 2000 m after releasing, 10 with a 6 to 7 m deposition height. There is no written information documenting this event. icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 11 NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Full Screen / Esc Fig.Figure 5. Damaged 5. Damaged school school building building (red (red ellipse) ellipse) and and houses houses (black(black ellipse)ellipse) due due toto thethe 1981 – house indicated in blue circle constructed in 2004. Printer-friendly Version –house indicated in blue circle constructed in 2004- Interactive Discussion 12 604 1 We identified 10 potential release zones in the first step using the DEM-based algorithm, see 2 Figure 6. In the second step, we checked the release zones manually and selected and 3 corrected the polygons, based on expert knowledge. Strong winds from the north and 70 cm 4 of freshly fallen snow (over 10-20 cm of old snow) had been observed by the villagers just 5 before the event. The release zones were located significantly higher than the Üzengili village. icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 6 Therefore, based on the Swiss Guidelines (Salm et al., 1990), we used a snow depth of 160 7 cm and included 50 cm of wind accumulation to calculate the release depths. NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close Fig.Figure 6. Identiﬁed 6. Identified release release zones zones by DEM-Based by DEM-Based release release zone zone generation generation approach approach (left); (left); corrected release zones to use in simulations at Üzengili (right) with a DEM resample of 10 m, Full Screen / Esc acorrected curvature release threshold zones of 3 to and use a roughness in simulations threshold at Üzengili of 0.03. (right) with a DEM resample of 10m, a curvature threshold of 3 and a roughness threshold of 0.03 Printer-friendly Version

Interactive Discussion 8 605 9 For Yaylaönü event all information was collected in the field by interviewing villagers and 10 observers. During the avalanche, strong winds from the south and more than 24 h of 11 continuous snowfall (90 to 100 cm) were reported. Three main release zones were identified. 12 Based on this information, the release depth was estimated to be around 160 cm (Figure 7). icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

J I Fig.Figure 7. Outlines7. Outlines of of the the 1981 1981 avalanche avalanche event event and and potentialpotential releaserelease zones (damaged (damaged school school indicated in blue circle, see Fig. 5). indicated in blue circle, see Fig. 5) Back Close Full Screen / Esc 1

Printer-friendly Version 2 7 Results and discussion Interactive Discussion

3 7.1 Applied scenarios 606

4 In Üzengili, the avalanche occurred at 7.30 a.m. and according to villagers’ observations came 5 from the left-hand side slope (in the flow direction) and filled the track with a deposit of 6 snow. Just a few minutes later a second avalanche came from the slope on the right hand side, 7 causing the damage, so we know that the two avalanches came just one after another. In order 8 to corroborate the villagers’ statements with numerical avalanche simulations, we used six 9 different elaborated scenarios (Table 1). RAMMS allows DEM modifications, for example, 10 updating the track with a previous avalanche deposit. For scenarios 2 to 6 we made the DEM 11 adaptation after releasing zone number 1. Then we released the other zones over the adapted 12 DEM to see the effect of filling the track by the first avalanche. We applied six different 13 probable scenarios, but only scenario 3 was able to cause an event as big as had been 14 observed; the results of scenario 3 are presented in the following sections.

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Full Screen / Esc

Printer-friendly Version Fig. 8. MaximumFigure 8. Maximum ﬂow height flow (left), height maximum (left), Maximum ﬂow velocity flow velocity (middle) (middle) and maximum and Maximum impact pressure (right).impact pressure (right) Interactive Discussion

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Full Screen / Esc

Printer-friendly Version Fig. 9. Avalanche aﬀected houses (red); non aﬀected houses (green); mosque indicated in blue Figure 9circle,.Avalanche see Fig. 4affected (Source: GDDA).houses (red); non affected houses (green); mosque indicated in Interactive Discussion blue circle, see Fig. 4 (Source: GDDA) 608

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Full Screen / Esc

Printer-friendly Version Fig.Figure 10. Avalanche 10. Avalanche impact impact pressure pressure at damaged at damaged mosque mosque area area (mosque (mosque indicated indicated in in blue blue circle – see Fig. 4, dashed black line indicate the outline of observed avalanche). Interactive Discussion circle-see Fig. 4, dashed black line indicate the outline of observed avalanche) 609 1

2 Yaylaönü Avalanche Site

3 At the Yaylaönü avalanche site, the villagers’ statements about a deposition height of 6-7 m 4 seemed to be realistic. Due to a narrow, channeled run-out zone, simulation results also 5 showed deposition to be around 7 m at the deposition zone, which complies with the 6 villagers’ statements (Figure 11). In 1981 the avalanche damaged the school building by 7 breaking doors and windows and uplifting roof, but it was not completely destroyed. Maybe 8 the damages at the building were caused by a powder cloud. A pressure of dense part of 9 avalanche less than 1-2 kPa could have been seen at the edge of the school building and seems 10 to be acceptable. The simulation results support this argument. A sketch based on villagers’ 1 statements drawing the outline of the 1981 avalanche (Figure 7) corresponds to the outline of 2 the modelled avalanche (compare Fig. 7 and Fig. 11). Impact pressure for the entire avalanche 3 track are given in Fig. 11; impact pressure forces calculated at the damaged school location

4 are shown in Figure 12. | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion NHESSD 2, 581–611, 2014

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

Back Close

Full Screen / Esc

Printer-friendly Version Fig. 11. FigureSimulation 11. Simulation result of result Yaylaönü of Yaylaönü project project area: maximumarea: maximum ﬂow flow height height (top) (top) and and maximum impact pressuremaximum (bottom).impact pressure (bottom). Interactive Discussion

Avalanche situation in Turkey and back-calculation of selected events

A. Aydın et al.

Title Page

Abstract Introduction

Conclusions References

Tables Figures

J I

J I Fig. 12. Damaged school during 1981 avalanche; impact pressure forces of around 1–2 kPa. Figure 12. Damaged school during 1981 avalanche; impact pressure forces of around 1-2 kPa Back Close

Full Screen / Esc 1

Printer-friendly Version 2 8 CONCLUSIONS Interactive Discussion 3 Turkey is a fast developing country, with more than 78 % of its territory in mountainous 4 areas. According to information from Ministry611 of Transportation, 15’700 km of new double- 5 lane highways have been constructed over the last ten years and there are plans to build 6 another 15’000 km of new railway lines by the year 2023. Furthermore, winter sport 7 activities have been increasing in Turkey during the last decade. It can be inferred that the 8 importance of avalanches as a major natural hazards in Turkey will increase substantially. 9 10 In Turkey, the proportion of avalanche fatalities who die in their homes is very high (87%) 11 compared with European and North American countries; for example in Switzerland and in 12 the United States less than 5% of the people who die in avalanches are killed in their houses. 13 This is the result of the long history of great efforts in avalanche research, hazard mapping 14 and mitigation measures established in this regions. 15 16 Avalanche mitigation requires a multidisciplinary approach. Thus in Turkey, a 17 multidisciplinary organizational structure which includes foresters, GIS experts, civil 18 engineers and geographers at the central and local offices of avalanche-prone areas are needed 19 to improve the situation. Legislation gaps must be filled in order to outline a concrete 20 definition of organizational duties and responsibilities. Avalanche mitigation needs the