The Inner Tay Estuary, the inner, western part of the Firth of Tay, stretching from the Tay Railway Bridge in the east to the Queen's Bridge over the River Tay in Perth and the bridge in Bridge of Earn on the River Earn. The estuary is one of the largest in eastern Scotland and is up to 2.5 km wide. The estuary consists primarily of inter-tidal sand and mud flats that extend seaward out to the main channel of the estuary, the majority of which lie on the northern shore. Landward of these are saltmarsh and Phragmites reedbeds. There are two large islands: Mugdrum Island opposite Newburgh and Moncreiffe Island immediately below Perth. The narrow form of the estuary and the large volume of freshwater from the Rivers Tay and Earn restrict the influence of salt water west of the Tayport narrows