Abdurrahim Aydın

The analysis of 2004 flood on Kozdere Stream in Istanbul

The climatic and physiographical factors of the Kozdere Creek Watershed are examined to find out the causes of the flood of August 11, 2004. Actual land use has been obtained from forest management stand plans and classified satellite images. The multispectral digital satellite data set belonging to years 1992, 1993, and 2005 was used to determine the status of land use. Physiographic factors, including the slope and the aspect, have been identified from digitized ortho-photo maps in the GIS environment. Since flow records of Kozdere are not available, flow values corresponding to different return periods were obtained using regression analysis of neighboring streams. No noticeable alteration of the land use occurred between 1992 and 2005. Since the physical factors are the same as they were during the 1985 rain, the flood after the 2004 rainfall cannot be due to the physiographical factors of the upper watershed. The existing channel in the neighborhood is not enough to convey even the 10-year return period flow. Thus, the 2004 flow did not fit into this cross-section and flooded houses on the alluvial fan. The cross-section of the Kozdere Creek passing through the PTT neighborhood should be increased, and the surface roughness should be decreased by covering the channel with concrete in order to prevent floods.

Assessment and analysis of rockfall-caused tree injuries in a Turkish fir stand: A case study from Kastamonu-Turkey

Rockfalls can cause serious damage to people, property, facilities and transportation corridors. Furthermore, rockfalls are major hazards in mountain areas with negative impacts on individual trees and forested ecosystems. We conducted a study of rockfall events on 117 mapped (91% of total trees in the stand with > 1.3 m in height and > 5 cm diameter at breast height) Turkish fir trees (Abies bornmuelleriana Mattf.) in a stand within the Kayaarkası-Topçular Village, Inebolu district, Kastamonu province of Turkey. The study site of 0.35 Ha is located on the transition zone of frequently passing rockfall fragments (∼ 40 cm in diameter) generally causing healable injuries. Parameters of trees and injuries were recorded and analysed as to injury number, height and size. Bivariate correlation analysis were used to investigate the relationships between: a) diameter at breast height and number of injuries per tree, b) diameter at breast height and total injury size, c) the number of injuries and total injury size and d) the number of injuries per tree and distance from the source of the rockfall area. Results indicate that the average height of injury, average number of injuries and average injury area to be 81.3 cm (STDEV: 49.8), 7.46 (STDEV: 4.4) and 628.6 cm2 (STDEV: 678.2), respectively. In total 84% of all injuries were recorded within 160° sector at the upslope side of trees and callus tissue that had closed wounds was observed in 79.1% of all injuries. Furthermore 14.5% of injured trees had callus tissue in the process of closing wounds while 6.4% of injuries had not formed any callus tissue. The most common injury types were bark and wood injuries. Bivariate correlation analysis indicated strong relationships between diameter at breast height and the number of injuries (rs = 0.524), injury number and total injury area (rs = 0.653) and distance from rockfall area and injury numbers relations (rs = −0.518). A weaker relationship was found between diameter at breast height and total injury area (rs = 0.363). These results indicate that bigger trees are more prone to rockfall injuries. As expected, trees further from the rockfall area seem to be less prone to rockfall injuries. From our results, it can be inferred that the protection of people and property can be increased through the maintanance of forest in areas immediately below areas prone to rockfall. This stand is still managed in selective forest management system. In order to protect the settlement at the deposition zone it has to manage for protective goals with uneven-aged and multilayered stand structure.