Swamp a special type of wetland. Swamp is a vegetated land area saturated with water. A swamp may have lake basin origin ie it may be formed when a lake basin is filled up as in the end stage in the life cycle of a lake. Swamps also originate on floodplains, on deltas near the freshwater lakes, along lake margins or near the springs. Swamps are located in wide and different geographic, ecological and physiographic environments. Hence its characteristics may be different in various locations. But two main common characteristics of swamps are domination of water and heavy vegetation. Swamps have spongy land. Swamp sediments are generally high in organic content but may also contain inorganic material. Swamp bottoms may be very soft having very low bearing capacity. Usually they do not contain false bottoms.
Swamps may be classified as saline or freshwater and also as tidal or non-tidal. Saltwater swamps develop under different conditions ranging from those of lagoonal environment along the Atlantic coast of North America to the mangrove swamps of sundarbans along the coast of the bay of bengal. These types of swamps are found in marine deltas. Newly accreted land, which receives inter-tidal mud, sand or salt flats with limited vegetation may also be called swamp. Inter-tidal forested wetlands such as mangrove wetland of Sundarbans are examples of saltwater swamp.
According to Dugan's classification of wetlands, these are estuarine inter-tidal wetlands. Some fresh water swamps such as floodplain swamps receive sediments containing different types of minerals each time they receive floodwater from the nearby streams or rivers. Under wetland classification of Dugan, they fall under Palustrine wetland, which are further sub-divided into two sub-classes, Emergent and Forested. Emergent types include permanent freshwater marshes and swamps with emergent vegetation the baseline of which lies below the water table for at least most of the growing season and permanent peat forming freshwater swamps dominated by Papyrus or Typha. Forested type includes shrub swamps, swamp forest eg Hijal (Barringtonia) forest of low land and peat swamp forest.
The terms swamp and bog are often used synonymously. But from the viewpoints of ecological, physical and chemical characteristics they are two different phenomena. The distinctive characteristic of bog is its floating vegetal mat, which swamp does not have. [HS Mozaddad Faruque]