آشکارسازی تغییرات کناری و شناسایی مناطق خطر رودخانه آجی‌چای در محدوده خواجه تا ونیار

 




Extended abstract
1- Introduction
Changes in the human environment in different periods and in different areas it is reasonable by the satellite images, aerial photographs and maps in certain forms are easily done. This is particularly important when the data becomes more critical in areas such as environment, agriculture; Natural resource management and river engineering are used (Pris and etal, 1997, 23). Therefore, in order to discover and detect changes that occur in different regions of the Earth Can ensure that remote sensing technology and satellite images in a sequence-specific forms used (Atood and al. 2005, 8)
 
And their results in the prediction, risk maps, choosing the right strategies to deal with behaviors sudden, More Accurate and more economical operation than to past and successfully implemented projects and structures of organizations and agencies On the rivers for future use. Thus, the geometry changes, the process of depositing and important morphological changes in the organization of the river, flood control, design of linear structures (roads, ...) Hydraulic (bridges, dams, ...) settlements and destruction of agricultural lands on the river and its margins are evaluation of morphological changes part of river Ajy Chay between Khaje to Vanyar, north east of Tabriz  46° 23'  55"  to  46°  34'  55"  along the eastern and 38° 07' 1"  to 38° 08' 40" north latitude Length of approximately 22 km with the aim of identifying risk areas to the lateral erosion investigated.
Of studies on the following can be noted:

 

 
Table 1. Studies on the topic of domestic and foreign





Names of authors


year


Topic


Result




Javaheri et al


2005


Morphological changes of Karun River


Development process is reversed Meander rings.




Karami


2007


Effective factors in the erosion of river Saidabad Chay


Identify areas with low risk, moderate to severe.




Dadrasi sabzevar


2007


Study privacy and deformation of river use Rs &GIS


GIS & Rs powerful techniques to study changes.




Aswathy et al


2007


Factors Influencing the Sinuosity of Pannagon River India


Vegetation and tectonics play a major role.




Lofthouse & Rabert


2008


Riffle-Pool Sequences and Meander Morphology


Both factors are influential in forming Meander.




Matti kummu et al


2008


"Riverbank Change Along The Mekong River.


Estimated average lateral erosion.





 




2- Methodology
How it works for this research have been carried out, the first report-required information and report about the range of research and library-based methods and field studies were collected. In the second stage, maps and aerial photos have been scanned, georefrenced, mosaic. In the third stage of the coastline extraction the River For a the time period three (years 1956, 1995 and 2008) Land and water border with digitization in eara gis To calculate the amount of surface erosion and sediment riverbank was done for three periods. To calculate the erosion and sediment to the coasts, along the river intervals of 250 meters, divided in three periods and than linear displacement due to sediment and erosion per meter on year for each period was obtained. At this stage the layer requirements such as erosion, land use, lithology, slope, floodingbed, and road digital and descriptive data were applied to each. Then all the layers due to the influence and reception of each factor over time and toward River erosion rate, converted to raster and weighting was ready. In the final stage of the layers and changes coastal The softwares environment Arc GIS 9.3,Excelwere processed and charts, tables and maps were extracted needed to determine the risk areas.
 
3- Discussion
Displacement of the river using three different data in software Arc GISby comparing the coasts the river in both periods 1956-1995 (39 years) and 1995- 2008 (13 years) was carried out . This study intended to measure changes in linear sides through time and identifies areas where it has been the erosion and sedimentation. Results of the linear by specifying Areas of erosion and sediment delivery and to chart the lateral rate the changes as a function of distance along the coasts (every 250 m) were mapped in the software Excel.

 

 
Figure. 1. The rates of bank movement (meter on year) as a function of distance along each of the left and right banks between the years 1956 to 1995.
 
 
Figure. 2.The rates of bank movement (meter on year) as a function of distance along each of the left and right banks between the years 1995 to 2008.
 

 

 Overall the amount deposited in the first period toward erosion in left bank 24 percent has increased and in right bank is approximately equal. Also in the second period, the amount of sediment toward erosion in left bank 43 percent has increased but in right bank 13% decrease show.
- Identification ofriskareas
Lateral changes in connection with other factors in region such as litho logy, land use, flooding bed, slop, linear structures (road) and residential over the steps to prepare the vector layers, table of data formation, Off-line buffer layers, Values, Raster to vector conversion and weighting of the layers in the software Arc GIS was evaluated and ultimately led to the identification of vulnerable areas, critical and very critical on the riverbank. It should be noted that the Values factors in the region due to the impact and reception of each factors towards time and toward Erosion River.

 

 
 
 
 
Table 2.Values layers in the region due to the impact and reception of each factors towards time and toward erosion river In the study area





weighting


Values


Distance from linear structures


Distance from residential structures


Distance from flooding bed


slop
(Percent)


Lateral erosion in year


lithology


Land use

 



Very critical


4


5-10 meter


50 meter


100 meter


0-9


6 meter high


sediments present


Agricultural


 




3


10-40 meter


100 meter


75 meter


9-18


4-6 meter


Marl and gypsum salt


Sparse pasture

 



critical

 



2


40-80 meter


150 meter


50 meter


18-27


2-4 meter


Marl


pasture

 



vulnerable

 



1


80 meter high


200 meter


25 meter


27 high


0-2 meter


Marl&conglomerate


Woodlands


 





 
Table 3. Percentage changes in risk zones along the riverbank between the years
 1956 - 1995 and 1995-2008.





Very critical


critical


vulnerable


 




0


14


9


right banks between the years 1956 to 1995




0


33


15


right banks between the years 1995 to 2008




0


+135


+66


Percentage changes




3


21


19


left banks between the years 1956 to 1995




2


15


9


left banks between the years 1995 to 2008




-3


-29


-53


Percentage changes





 

 

According to Table number 3 Vulnerable areas and critical right bank In the second period towards the first period shows the 66 and 135 percentage increase and in none of the courses There are no very critical areas . While the vulnerable areas, critical and very critical in the second period towards the first period shows the 53, 29 and 33 percentage decrease. Finally the combination of maps of risk areas in left to right on the bank For both periods 1956-1995 , 1995-2008 was prepared and areas where of vulnerabilities, critical and very critical repeats were identified (Figure. 3 &4).

 

 
 
Figure 3. Risk areas map of the right bank during the both period 1956-1995, 1995-2008.
 
Figure 4. Risk areas map of the left bank during the both period 1956-1995, 1995-2008.
 



4- Conclusion
The results of maps and charts show that in both periods right bank of erosion more than left bank and the second term right down the bank deposit and left the bank deposit has increased. Considering that the second term on the right bank more erosion than deposition but also increase the deposition in left bank the erosion can be seen that this phenomenon is due to the high sensitivity right bank to erosion, less shrub cover, accumulation of sediment erosion in the left bank and the relative resistance to against erosion is on the left bank. Cause an increase in vulnerable areas and right bank of the critical in the second period than in the first period and less vulnerable areas, the critical and very the critical left bank in the second period than in the first period can be understood that it was already too much discharge and erosion on the left bank to slip and fall are also effective but with a little discharge due to the uneven impact of the lower left of the bank and the right bank, mostly in left bank sediments have accumulated. But the right bank due to flow in alluvial deposits still contain high erosion potential. Obviously, the results of this research by other professionals can be effective in preventing disaster. In this study, merely the river Lateral changes over time has been and comment on its applications to professional experts in various fields of environmental and engineering.