1. RAINFALL TRIGGERED LANDSLIDES IN TRABZON PROVINCE, TURKEY
E. Eris
Ege University, Izmir
H. Aksoy
Istanbul Technical University, Istanbul

2. Disasters in Turkey Disaster Proportion (%) Earthquakes 61 Landslides15
Floods 14
Rock falls 5
Forest fire 4
Snowslide 1
• 25% of country area is exposed to landslide hazard.
• 11% of total population is located in landslide areas.
• 15 % of total disaster losses are due to landslides.

3. Spatial distribution of landslide events in Turkey

4. Trabzon Province

5. Trabzon Province
Elevation increases from sea level to reach up to 3000 m.
Generally, mountains, hills and high plateaus take part in inner lands of the region.
Trabzon has mild and humid climate with a heavy uniform rainfall and relatively warm temperatures all year round.

6. Annual rainfall of 9 rainfall gauges in Trabzon

7. Landslides & Rainfall
Climate type map
Landslide density map

9. Source: Disaster and Emergency Presidency (AFAD)
Between the years of

10. Landslides & Rainfall Uzungol gauge Trabzon gauge Event date
21 November 2009
2 people dead
Trabzon gauge
Event date
19-20 June 1990
56/65 people dead

11. Threshold Analysis
The thresholds are usually obtained by drawing lower-bound lines to the rainfall conditions resulted in landslides.

12. Threshold Analysis
2.5 h  D  40 h
The most important 27 rainfall-triggered landslides between 1990 and 2009.
Local and national administrations, technical and scientific articles, thesis and internet news

13. Some of rainfall intensity-duration threshold equations
Study by
Area
Equation
Caine (1980)
Over the world
I= D-0.39
Cancelli and Nova (1985)
Northern Italy
I= D0.78
Wieczorek (1987)
California
I= D-1
Crosta and Frattini (2001)
I= D-1
Aleotti (2004)
Italy
I= 19 D-050
Guzetti et al. (2007)
Mid-latitude climate for D<300h
I= 18.6 D-0.81
Mid-latitude climate for D>300h
I= 0.82 D-0.19
Dahal and Hasegawa (2008)
Himalaya, Nepal
I= D-0.79
Baltacı (2010)
Trabzon
I= D
Akçalı and Arman (2013)
Trabzon for D<6h
I= D-2.33
Trabzon for D>6h
I= 2.75 D-0.63
This study (2014)
I= 20 D-0.80

14. Some of rainfall intensity-duration threshold eq.
According to Guzzetti et al. (2007)
power is between and for mid-latitude climates
power is between and for the mountains and cold climates

15. Conclusions
The proposed equation seems to be a reasonable approximation when it is compared to previous equations developed from data of landslides in Trabzon.
For the risk mitigation studies, landslide early warning systems can be implemented by using rainfall-landslide thresholds as proposed in this study.
The proposed empirical relation takes rainfall into account only; it does not account for other factors causing landslide such as slope, land use, vegetation, etc.
There are only a few intensity-duration threshold studies on landslides at local scale in Turkey. At present, such a general threshold relation is not available for the whole country. This can be considered an important gap in terms of both research and practice.

16. Thank you… Ebru Eris ebru.eris@ege.edu.tr Hafzullah Aksoy