evaluation effect of tectonic activity in regulation rivers channel case study: tajan river

the tajan river is one of the most important rivers in the north of iran. it seems that in respect of its meander design and pattern, passing over the block's fault and deviations along its way, it's influenced with active neotectonically movements in the region. although being meander in rivers, in the level of a flood water field with very low gradient, isn't unexpected but existent abnormal like unusual contortions, local expand of meanders, braded formation and sudden changing in ways in different periods, are targets of passing from an active tectonically area. hence, to recognize the method of acting in these tectonically activities and to recognize the amount of effects of tectonically movements in modeling of rivers behavior, some geomorphologic indexes such as sl, smf, af and etc, are used. because the model of expand & evolution of drainage networks, is one of some indexes which are more sensitive about changes of earth made activities. in this research to examine the changes of river headstock, some aerial photos of several periods in scales of 1:20000 & 1:55000 and satellite image of landsat tm and field processes in two turns were used. also soft wares like ilwiss 3.3, arcgis9.1 and photoshop was used in sketching & cartographic analysis. this research's results show that region in aspect of neotectonically or young tectonically is active because of coefficients obtained from geomorphology's indexes and geodynamic station's data but the amounts of activities aren't the same among regions. in the other side, 4 old waterways were revealed by relying to morphological witnesses through studding the aerial photos, geologic map and the important faults of region in cross of tajan river and topographic quantitative analysis and the type of tajan river.