Chapter 2 Physical Features

Middle Kolab Multipurpose Project Detailed Project Report CHAPTER 2 PHYSICAL FEATURES 2.1 GENERAL There are few places on earth that are special and Odisha is one of them. It is a fascinating land filled with exquisite temples, monuments and possessing beaches, wild life, sanctuaries and natural landscape of enchanting beauty. The project area falls in Koraput and Malkangiri district of Odisha having its geographical area as 5294.5 Sq. Km. The district is bounded by Rayagada and Srikaklam district on its East side, Bastar district on the west, Malkangiri district on South-west side, Nabarangpur district on north and Vishakhapatnam on south. Malkangiri and Koraput districts are situated at 18°35’ Latitude and 82°72’ Longitude at an average elevation of 170 and 870 m respectively from mean sea level. The district’s demographic profile makes it clear that it is a predominantly tribal and backward district with 56% tribal and 78% of the rural families below poverty line (BPL). The region is characterised by high temperature and humidity in most parts of the year and medium to high annual rainfall. There is a considerable extent of natural vegetation in this region. The hydrographical features also reflect these effects. The chapter describes the general topographical and physical features of the Kolab basin and the project command area. 2.2 PHYSIOGRAPHY Odisha State lies within latitude 17° 48 to 23° 34 and longitude 81° 24 to 87°29 and is bounded on the north by Jharkhand, on the west by Chhattisgarh, on the south by Andhra Pradesh and on the north-east by West Bengal. On the south-east, is the Bay of Bengal with a coastline of 480 Km. The State consists of 30 districts covering an area of 1,55,820 SqKm.On the basis of homogeneity, continuity and physiographical characteristics, Odisha has been divided into four major regions: 1. The coastal plains in the east Chapter-2: Physical Features 2-1 1 Middle Kolab Multipurpose Project Detailed Project Report 2. The middle mountainous and highlands region 3. The central plateaus 4. The western rolling uplands The principal rivers include the Mahanadi, Brahmani and Baitarani, the others being the Subarnarekha,Indravati,Machhkund,etc. The Chilka Lake, the widest lagoon in India, is a prominent coastal feature in the State. The Odisha Coastal Plains or Utkal Plains are the depositional landforms of recent origin and geologically belong to the Post-Tertiary Period. The 75 meter contourline delimits their western boundary and differentiates them from the Middle Mountainous Region. This region stretches from the West Bengal border, i.e. from the River Subarnarekha in the north to the River Rushikulya in the south. This region is the combination of several deltas of varied sizes and shapes formed by the major rivers of Odisha, such as the Subarnarekha, the Budhabalanga, the Baitarani, the Brahmani, the Mahanadi, and the Rushikulya. Therefore, the coastal plain of Odisha is called the "Hexadeltaic region" or the "Gift of Six Rivers". It stretches along the coast of the Bay of Bengal having the maximum width in the Middle Coastal Plain (the Mahanadi Delta), narrow in the Northern Coastal Plain (Balasore Plain) and narrowest in the Southern Coastal Plain (Ganjam Plain). The North Coastal Plain comprises the deltas of the Subarnarekha and the Budhabalanga rivers and bears evidences of marine transgressions. The Middle Coastal Plain comprises the compound deltas of the Baitarani, Brahmani and Mahanadi rivers and bears evidences of past 'back bays' and present lakes. The South Coastal Plain comprises the laccustrine Plain of Chilika Lake and the smaller delta of the Rushikulya River. The middle mountainous and highland region covers about three-fourth of the entire State. Geologically it is a part of the Indian Peninsula which as a part of the ancient landmass of the Gondwanaland. The major rivers of Odisha with their tributaries have cut deep and narrow valleys. This region mostly comprises the hills and mountains of the Eastern Ghats which rise abruptly and steeply in the east and slope gently to a dissected plateau in the west running from north-west (Mayurbhanj) to south-west (Malkangiri). This region is well marked by a number of interfluves or watersheds. Chapter-2: Physical Features 2-2 2 Middle Kolab Multipurpose Project Detailed Project Report The Eastern Ghats is interrupted by a number of broad and narrow river valleys and flood plains. The average height of this region is about 900 metres above the mean seal level. The highest peak is Deomali. The central plateaus are mostly eroded plateaus forming the western slopes of the Eastern Ghats with elevation varying from 305–610 metres. There are two broad plateaus in Odisha: (i) the Panposh – Keonjhar -Pallahara plateau comprises the Upper Baitarani catchment basin, and (ii) the Nabrangpur – Jeypore plateau comprises the Sabari basin. Western rolling uplands are lower in elevation than the plateaus having heights varying from 153 metres to 305 metres. Physical Map of Odisha Chapter-2: Physical Features 2-3 3 Middle Kolab Multipurpose Project Detailed Project Report 2.3 STRUCTURE AND TECTONICS The regional trend in the Eastern Ghats belt is dominantly N.E. – S.W. in the south – western part (Koraputdistrict) which gradually changes to N.-S. in the western part ( Kalahandi district ) and then to E.N.E.- W.S.W. through N.E.- S.W. in the northern part . The E.N.E. - W.S.W. trend in the Bolangir district abruptly changes to N.W. - S.E. trend ( Mahanadi trend ) and continues in the north – eastern part of the orogen ( eastern Phulbani , Dhenkanal, Cuttack and Puri District ) until it disappears under the coastal sedimentary cover . This spectacular change in the trend is considered to be due to major cross folding alone a N.W. – S.E. axis. That superimposed or cross folding had taken place is amply evidenced from the result of structural studies carried out several workers in part of the belt. Further, it is likely that the emplacement of the anorthosite bodies in the Puri and Bolangir districts is controlled by these cross fold movements. The abrupt change in Mahanadi trend in the north – eastern part is interpreted to be due either to the presence of large steeply plunging folds or to the later movement on the marginal part of the craton (Chatterji et al, 1971). 2.4 REGIONAL GEOLOGY AND STRATIGRAPHY The strata of Orissa state forms a part of the north eastern extension of the Peninsular shield. Orissa state is by and large underlain by Precambrian rocks. A little less than 25 percent of the total area of the state is constituted of the Phanerozoic rocks, quaternary formations and the recent to sub-recent alluvium. Particularly in Koraput district, the existence of remnants of Laterite and Bauxite covered plantation surfaces (erosion plains) at different altitudes leaves no doubt that the land was subjected to one of the most epeirogenic movements, probably in the quaternary period. It is proposed to include the group of Meta sediments and basic rock (Sukma Group) occurring in the South-Western part of Orissa in Koraput district in the iron ore group. However, the trends vary from north-south in the Sukma rocks (Koraput) to east- western in the Sambalpur district. Orissa has been divided into five major morphological regions, which are as under: Chapter-2: Physical Features 2-4 4 Middle Kolab Multipurpose Project Detailed Project Report 1) Orissa Coastal plain in the east. 2) The middle mountains. 3) The Central Plateau 4) The Western rolling uplands 5) The major flood plains The Kolab/Sabari basin lies in Nabarangpur-Jeypore Plateau. The Plateau is most eroded plateau forming the western slopes of Eastern Ghats with elevation varying from 305-610 meters. Dam Site Area-Geological Set up The river Kolab/Sabari flows in S280W direction at the proposed dam site. The rocks exposed on both the banks at site are mainly banded quartzite with shales. The quartzites are also generally exposed in the river bed section at the site but the length of the dam including dykes shall be of the order of 6000m and a number of dykes are also required at the proposed site. The rocks in the area are well jointed and are traversed by Shear Zones in different direction. Bane of Orissa –Cyclones-Vulnerability and Impact Vulnerability The Indian sub-continent has a long coastline of 8.41 Kilometers and is highly prone to tropical cyclones, the majority of them have their initial genesis over the Bay of Bengal and strike the east coast of India. On an average, five to six tropical cyclones occur every year of which two or three could be severe. More cyclones occur in the Bay of Bengal than the Arabian Sea and the ratio is 4:1. In Orissa, the cyclones are usually experienced in the post monsoon period, normally in the month of October and November. Impact: At this time, the Kharif paddy is generally in the flowering stage. The flowers being blown off by strong winds, damage the paddy crop seriously. When lashed into severe cyclonic storm, the very economic structure gets hit in the Coastal districts. Chapter-2: Physical Features 2-5 5 Middle Kolab Multipurpose Project Detailed Project Report The fertile affected land of the Coastal districts may extend about 25 Km inland. 75% of the people in the area depend upon agriculture and 5% on fishing. About 90% population lives in thatched roof houses. The Communication system of the area is extremely poor. The weaker sections of the society in these coastal districts have not been able to improve their economic condition. On account of frequent floods, saline inundation and severe cyclones, the state in the recent years has suffered extension losses due to super cyclones.

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