International Journal of Engineering and Technical Research (IJETR) ISSN: 2321-0869, Volume-1, Issue-7, September 2013 Navigation channels and tidal power plants (250 mw) for Chennai City R. Ramasamy, SP. Subramanian and R. Sundaravadivelu Kortralaiyar River and Araniyar Rivers, Pulicat Lake and Abstract— The Chennai City is blessed with rivers of Adayar, Buckingham canal over 120 km stretch. Inadequate Coovum, Kortralaiyar, Ennore creek, Araniyar Rivers, Pulicat environmental monitoring of these water bodies, they are Lake and interconnecting Buckingham canal. Training walls of silted and contaminated with pollutants and sewerages owing 2500 m lengths, with submerged barrages at about 500 m inside to urban development and sewage disposal. Of late, cleaning the entrances are to be constructed to generate rip currents, and monitoring of river flows of Coovum and Adayar Rivers, which prevent deposition of sedimentation and mouth closure by littoral drifts. A navigation channel in the Coovum River of 70 are major problem because of periodic mouth closures of m width to 64 km long to Thiruvallore may be constructed with these rivers by the movement and deposition of littoral drift 5 lock and gate systems to rise and lowering boats and barrages. sediments. The prevailing wind blows for more than 9 months Another navigation channel for 36 km long in the Adayar valley towards NE and littoral drift moves towards NE rate of +0.14 up to Karisangal village may be constructed in similar manner. m3/ month with depositional environment and -0.04 m3/ The entries of tidal waters far into Thiruverkadu, month towards SW with erosional effect along the seashore of Thiruneermalai, and Buckingham canal flush out sewerages Chennai [1]. Therefore, most of the river mouths in Tamil far into the sea. The dredging and deepening of these waterways Nadu are closed by sand bar of varying widths 10 to 150 m -3 m msl always allow groundwater seepages enhancing river from SW to NE. When the sun, the moon and the earth form a discharge potential. Disposal of sewerages and waste waters further increase this potential. Beyond these tidal basins, both line, the reinforced spring tide rise happens twice a month Coovum and Adayar valleys, dredging up to 5 m depth is during new moon and full moon times and the mean spring sufficient. Below the valley floor sufficient groundwater seepage tide range in Chennai harbour is hardly 1.1 m [1]. When the o enhance waters for navigations in these water ways. sun and moon are separated by 90 when viewed from the Construction of lock and gates at suitable places always Earth, the tide’s range at its minimum and the neap tide range maintain sufficient water level for navigation. Using volume of in Chennai harbour is 0.4 m only. However, in order to clean specific yield of groundwater supply (>10 l/s), river water and the river valleys and to solve associated environmental sewerage discharges, assumed potential of river-discharges and problems, it is necessary to extend tidal channels far into the tidal prisms of saline water are calculated. The volume of water land over a distance of 25 km to the interior of the city. discharge of tidal prism has potential to generate 250 MW power by constructing suitable barrage type of tidal power Navigation is the cheap transportation system. Network of plants at the mouths of Coovum, Adayar, Muthukkadu, Ennore navigation canals, not only solve transportation problem of Creek, Karungali and Thangaperumbalam near old Pulicat the growing city, it also cleans the city and promotes Lake. These plants can work for 20 hours per day. To reduce aquaculture. In addition to these networks of transporting environmental problems plants may be constructed following system, it can supply enormous quantity of water to be the model of Severn Tidal Power Plant in United Kingdom. discharged into the sea. In order to maintain and regulate river flow, a tidal channel is necessary for a distance of 2.5 km Index Terms—Adayar River, Chennai City, Coovum River, from the shoreline into the sea where optimum depth of 7.5 m Navigation channels, Tidal Power plants. depth prevails. The width of the tidal channel may be designed according to the existing width of the river mouth. Tidal power generation depends on the volume of water I. INTRODUCTION discharged through tidal channel. Allowing tidal water to The growing Chennai City needs more electric power supply considerable distance into the city by deepening river valleys for its domestic and industrial needs. Chennai has more than and river mouths and constructing suitable structures to arrest 120 km length of coastline. In India only a few places like mouth closures, it is possible to generate tidal electric power. Gujarat and Bengal coastline tidal range exceeds 5 m. Even in The paper highlights, the possibility of development of these places installation of tidal power stations is still has a navigation channels and installation of tidal power plants. critical issue. It is known that to generate tidal electric power minimum of 5 m mean tidal range is required. On the other hand Chennai is blessed with Coovum River, Adayar River, II. MOUTH STABILIZATION The mouths of Coovum River, Adayar River, Kortralaiyar Manuscript received August 29, 2013. River, Araniyar River, Muthukkadu River, Karungali and R. Ramasamy, Department of Ocean Engineering, Indian Institute of Thangalperumpallam are closed by development of sandbars, Technology-Madras, Chennai-36, India. SP. Subramanian, Department of Ocean Engineering, Indian Institute of spits and shoals at their mouths. The Pulicat Lake mouth Technology-Madras, Chennai-36, India. located at 650 m NE of Thangalperumpallam (13.390 N & R. Sundaravadivelu, Department of Ocean Engineering, Indian Institute 80.332 E) where the old Pulicat mouth was closed after of Technology-Madras, Chennai-36, India. opening a new mouth (13.469N &80.311E) at 5.75 km NE of . Pulicat Town in Andhra Pradesh. Though, PWD has taken 13 www.erpublication.org Navigation channels and tidal power plants (250 mw) for Chennai City many measures to arrest closure of Coovum mouth to discharge the flow of Coovum River water, the problem of mouth closure is not yet solved. Although two groins one lying in the north trends N 130oE for a distance of 140 m into Fig. 3. A tidal channel 2500 m long from the mouth of the sea and other in south trends N60o E for a distance of 150 Coovum River with 2 tidal power stations at 1000 m intervals m, the end points of the groins meet hardly a depth of 2 m and a submerged barrage 7.5 m above sea bed and -2.5 m contour line. The average storm surge is 3 m [1]. Waves below CD near the entrance. The width of tidal channel may produced by strong winds and spring tides break at these be widened from 70 m to 200m shallow depth and deposits sand at its mouth. The failure of the structure is due to insufficient length of groins and absence of a submerged barrage sufficiently inner portion of the groins to produce rip currents. Other unprotected mouths Fig. 4. A tidal power plant 200 m long between training walls of various rivers along the coastal tract of Chennai are closed. following the model of Severn Tidal Power Plant at United The slope gradient of near shore regions in the sea is very Kingdom gentle 1:350. In order to reach 7.5 m depth, it is necessary to go 2.5 km inside the sea. At this depth waves oscillate without III. GROUNDWATER POTENTIAL any breaking. For construction of a tidal channel, the channel The Chennai Basin is situated between latitudes 12°40'N and depth might be maintained for 7.5 m depth, so that any storm 13°40'N and longitudes 79°10'E and 80°25'E at the north east surge tides rarely exceeds of 15 m wave height. Two parallel corner of Tamil Nadu. The total area of the basin is 7282 km². training walls for a length of 3 km from the shoreline into the District Resource Planning maps for Kancheepuram, sea, perpendicular to the shore on the mouth are essential to Thiruvallore and Chennai [2] indicate specific yield of regulate river water flow into the sea. Minimum 5 m depth groundwater potential is >10 liters per second along the river foundation column should be treated. Further a submerged valleys and along the coastal tracts. Along the river valleys barrage of 5 m height above seafloor (Fig. 1) should to be pool of water cutting groundwater table are seen at number of constructed at a distance. The submerged barrage prevents places. The groundwater table contour maps show that sand migration into the tidal channel by generating rip groundwater table is cut the topographical elevation contour currents in front of the barrage. By this construction littoral map often less than 3 m depth below ground level in these drift sedimentation in front of the channel will be prevented. alleys. Many intersecting fault lineaments interconnect deep The development of rip currents also prevents littoral drift confined aquifers with shallow unconfined aquifers in the sedimentations of the southern side and scouring on the Chennai basin [1]. A NE-SW trending fault lineament northern side of the tidal channel. intersects Cheyyaar, Adayar, Coovum, Kortralaiyar Rivers and boundary fault of Pulicat Lake. Numerous buried channels with groundwater potentials are seen along his lineament. The Pulicat Sub basin of Cauvery Basin is more than 3000 m deep near the coast. However porosity and permeability of local soil cover and rock types vary locally. Dredging of 3 m below the riverbed will yield sufficient quantity of water for navigation with installation of lock and gate system in the upstream side.