Terrace

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Terrace flat topographic form at the ultimate stage of its building up resulting from the accumulation of material, most often coarse, degraded by later dissection. The materials may have been deposited by streams (fluvial terraces) or lakes (lacustrine terraces) or the sea (marine terraces) and may dominate the present level of the stream, lake or sea. Bangladesh contains hills (12%), terraces (8%) and floodplains (80%). The terrace areas include the madhupur tract, barind tract primarily and a small area in Akhaura.

Geologically, the Madhupur and Barind tracts belong to Plio-Pleistocene Terrace deposits. The Madhupur and Barind tracts are underlain by unconsolidated Madhupur Clay. These tracts are broken into several fault blocks, the surfaces of which are a few meters higher than the nearby floodplain land. The Madhupur clay has not been folded like the rocks of hill areas and it has been dissected by more rivers and streams compared to the Barind Tract. It also has a more complex relief pattern. Five kinds of relief pattern, namely, level, poorly-drained areas (occupies most of the Barind Tract and a few small areas of the Madhupur Tract), high uplifted areas (15m high western edge of the Barind Tract), broadly dissected areas (mostly on the Madhupur Tract, minor areas in the Barind and Akhaura terraces), closely dissected areas (on the Madhupur Tract only) and broadly dissected valleys (on the Madhupur Tract). Diverse kinds of soils have developed on these terraces. These include deep and shallow brown terrace soils, brown mottled terrace soils, deep and shallow terrace soils, grey valley soils, basin clays, non-calcareous and dark grey floodplain soils and grey piedmont soils. [Md Mizanur Rahman Bhuiyan]

See also physiography.