fa تاثیر عوامل هندسی بر جزر و مد در خورهای طویل شرايط محيطي و زيست محيطي Environmental Study مقاله پژوهشي Research Paper Tidal behavior of esturies is more complicated than open seas. It arises from the effects of geometrical parameters. Also other parameter such as wave reflection from the end of estuaries, sieche, bed friction and coriolis forces cause the water level changes in the esturies to be several times as in the open sea. This paper evalutes the effects of gemetric parameters (such as length, wide and depth), on the tidal behaviour of macro-tidal estuaris. It was done specifically for Mahshahr estuary, located in north west of Persian Golf. This research was done by using numerical simulation and field measuements. As a result, it can be said that: wide of estuary has no effect on phase and high tide elevation in the estuary. Also reduction of water depth causes the phase increament and reduction of tide amplitude, while it has no effect on high tide elevation in the estuary. It also shows that, flood wave transformation from sea into the estuary is associated with phase lag. The amount of this lag is about 10 and 20 minutes per kilometer of the channel length in the deep part and shallow part of the estury, respectively. The results also show that Mahshar estuary to behave as a rectangular–shallow-long estuary. long estuary, tide, macro-tidal, Mahshahr estuary, numerical modeling 89 104 http://marine-eng.ir/browse.php?a_code=A-10-32-1&slc_lang=fa&sid=1 Ali Karami Khaniki علی کرمی خانیکی akk7239@yahoo.com 1003194753284600659 1003194753284600659 Yes Departmet of Coastal Protection, Watershed Management Research Institute مرکز تحقیقات حفاظت خاک و آبخیزداری fatemeh Ziaeyan فاطمه ضیائیان 1003194753284600660 1003194753284600660 No Science and Research Branch, Islamic Azad Uni دانشگاه آزاد اسلامی، واحد علوم و تحقیقات