Chilka Lake is probably a deltaic lake. If we consider that the delta starts at the western end of this lake, the deltaic arc of the Mahanadi with reference to a straight line joining the western end of the Chilka Lake with the shore point on 21° N, is projected to the extent of about 60 km. The length of this arc is about 300 km long.
The markedly arcuate delta is related to the enormous amount of sediments from the large basin of rugged terrain associated with intense erosion under hot and humid monsoonal climate. This delta and other deltas of the eastern coast of India would have been more lobate had they been in protected marine waters and had been free from cyclonic storms and ocean currents.
“The Mahanadi delta is triple delta where deltaic sediments of the Mahanadi, the Brahmani and Baitarani” are dropped. Within the arcuate bulge, the distributaries are marked by estuarine inlets with inter-stream headlands. The structural bases of the Mahanadi delta are different from those of the Ganga.
The Ganga delta is located at the seaward edge of a sagging deep depression associated with the Himalayan mountain building. The Mahanadi, on the other hand, occurs on the rigid peninsular platform. The Mahanadi basin is believed to correspond with the Permo-Carboniferous rift valley but the present delta is probably much broader than the original graben and the deltaic sediments occupy a wider region.
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“The khondalite hills and other crystallines covered with laterites near Cuttack” and further northeast indicate the relative shallowness of the sedimentary cover over the rigid shield. North of Puri, beneath the alluvium is Miocene-Pliocene marine sandstones indicating geologically recent elevation of the ‘coastal plain’, occupied by the delta.
The alluvium of the Mahanadi delta is akin to the Older Alluvium and different from the Newer Alluvium, which occupies the Ganga delta. Some islands have grown in protected regions, e.g., behind the spit that encloses Chilka lake and off the mouths of the Brahmani and Baitarani, e.g., Shrott’s island and Wheeler island. The latter are probably due to deltaic sedimentation. Some deltaic lakes also occur, e.g., Sar lake (c. 6 km by 4 km) and Samang lake (c. 3 km by 1.5 km). These fresh water lakes are the old beds of distributaries,