The effect of side-channel sediment source on downstream fining trend of Haram- Abad river watershed (western Malayer plain)

Haram- Abad river basin (area = 2965 Km2) is an elongated basin located in south of Hamedan Province and occurs in the Sanandaj- Sirjan structural zone. 1392 km2 of this region is located in the western Malayer plain. Five lithofaceis were recognized in the river sediments: Gms, Gm, Sh, Sl and Fm and Fr. The river sediments are very poorly sorted, positively skewed and platykurtic. Four discontinuities were recognized in in the downstream decrease in the gravel percent. They occur as a result of the entrance of side-channel sediment sources (i.e. alluvial fan, tributaries and colluviums) to the main-river channel. Increase in the gravel percent is less significant (3-8%) in those tributaries with lower slope and slate and schist lithology than the tributaries with higher slope and granite and limestone lithology (25-32%). This shows the provenance lithology is also important in the downstream fining trend of the studied river.