LANDSLIDES POSITIVE ENVIRONMENTAL IMPACT, RECENT AND HISTORIC CASES FROM ZAGROS AND ALBORZ MOUNTAINS, IRAN

Numerous major landslides are recognizable in the Zagros and Alborz folded belts at the southwest and north of Iranian plateau. Alternation of competent and incompetent geological formations, active tectonic, rapid erosion and high magnitude earthquakes created these landslides.

Roads, major crude and gas pipelines crossing these mountains and streams are under influence of active landslides hazards and related economic consequences; while historic and Quaternary landslide’s outcomes are playing a positive role in economy and social life of the people.

Studied nine lakes and lake deposits of the Alborz and Zagros Mountains shows that they are created by blocking of the valleys and streams with major landslides. These landslides may had hazardous impacts during the sliding at their site or their upstream by unpredicted lake creation and expansion, but now their outcome are more beneficial and valuable asset for the public and economy of the region.

Among those, Valasht, Tar, and Havir lakes in the Alborz and Gahar Lake in the High Zagros are created by major historic landslides. They are significant environmental attraction and recreation spots near Chalous, Damavand, Doroud and Boroujerd cities. Biregan, Dasht-e-Room, Sousan, Shrin-Bahar and Dareh-Shahr flat and nutritious lakebeds in the Zagros Mountain’s valleys are major cultivation points and site of numerous towns and villages. Dareh-Shahr lake-deposits with about 200 Km² coverage is created by blocking Seymareh and Kashkan Rivers by massive Seymareh Landslide collapsed from north flank of Kabir-Kuh anticline. Cities of Dareh-Shahr and Pol-e-dokhtar and thirty more villages are built near or on these lake beds benefiting from farming and harvesting twice annually on the Seymareh Landslide lake beds.