Hydrogeomorphological studies in the Trichirappalli environs,Tamil Nadu, India using Remote Sensing technology
Pediplain:
In this unit developed as a result of continuous processes of pedimentation. The altitudinal variations is relatively high for rolling plain and is about 5 -10 m. In this horizon are exists irregular dissected portions with a number of gully are present. The pediplain with sedimentary rocks exposures (Upper Cretaceous formations) are to be found in the north-eastern part of the area. This formed due to intensive weathering under semi arid climatic conditions, representing final stage of the cyclic erosion (Knig, 1950 and Sparks, 1960). These are identified in the imageries grey tone on false colour composite (Ghose, 1993). Groundwater prospects in this unit good due to the moderate thickness (15-20 m) weathering materials (Prakash and Mishra 1993). Pedipalin are also found in the western part of the area.
Pediment Inselberg
Pediment is isolated residual hillocks being remnants of weathering and denudation. Inselbergs are mostly barren, rocky, usually smooth and rounded small hills. This unit occurs in the northern, north-western and south-western parts of the study areas. From this groundwater point of these are all treated neither containing nor transmitting of waters i.e. aquifuge nature. Mostly acts as run off zones.
allow pediments:
This unit is basically pediments zone and various soil types cover over the pediment materials. This unit is very low weathering thickness of the materials up to 5 m . These units characterized by very high runoff zone and poor groundwater recharge horizons. These units are found to be north, north-western, central, south and south-western parts of the study area.
Buried pediments (medium):
This units is moderately weathered with a thickness varies from 5-20 m . The groundwater prospects in these units are moderately good. In this zone are found close of the Cauvery River, south-central, southwest and southern parts of the study areas.
Buried pediments (deep):
These units mainly due to highly weathering of the hornblende biotite gneisses under semi-arid climatic conditions. In this unit infiltration is moderately good. The thickness of weathered zone varies from 10-20m and favours a good amount of water to circulate within this zone before reaching the deeper fracture zone. Groundwater potential zone is very good and this unit is suitable for dugwell, dugcumbore wells and bore wells. Buried pediments are found detached pockets of the entire study area.
Flood plain:
This is the youngest geological unit and including various landforms formed by fluvial action. This consists of sand, silt and clays and facilities channel bed infiltration. It is a highly permeable zone helping in partial bank recharge and subsurface flow groundwater occurs under semi-confined to perched water table conditions with shallow water levels. Groundwater prospects in flood plains are almost invariably found to be good (Sharma and Jugran 1992). In this units are exists all along the Cauvery river courses.
Deltaic plain:
Deltaic plain is the major geomorphic unit in the area, and is under intensive cultivation. It is occupy about twenty percentage of the area and is comprised of finer loosely packed sediments. Within the deltaic plain some localized low lying areas, affected by water logged and soil salinity or alkalinity are found. The water logging and salinity problems may be due to the rising the water level, low lying topography and seepage from canals etc., This zone are found to be southeast, east, north-eastern parts of the study area.