Available online at www.sciencedirect.com ScienceDirect Aquatic Procedia 4 ( 2015 ) 341 – 348 INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015) Effect of Mega Bridge on Hydro-morphodynamics of Waterfront Facilities in Wide Estuarine Harbours- A Sustainable Development A.A. Purohit a*, M.M. Vaidya a, K.A. Chavan a, M.D. Kudale a aCentral Water & Power Research Station, Khadakwasla P.O, Pune 411024, India Abstract Mumbai being traditionally the epicentre of India’s commerce, the narrow stretch of land (Mumbai Island) has seen a steady increase in population despite obvious spatial constraints. Hence for easing the pressure on the island city, development of Navi Mumbai on east has been identified. However lack of easy connectivity to Navi Mumbai has stunted its growth and pressure on Mumbai’s infrastructure viz. roads/bridges continues to mount. As such to cater the need of road traffic/avoid traffic jams, it is inevitable to have Mega Bridge (MTHL) connecting Mumbai to Navi Mumbai spanning across entire width (17 km) of wide estuarine region, wherein major ports viz. Mumbai and Jawaharlal Nehru exist. These ports are facing problem of increased siltation. Hence to assess effect of MTHL consisting of hundreds of piers, which may have detrimental effect on existing waterfront facilities from hydro-morphodynamic aspect, studies are essential to ensure that development is sustainable. The effect of MTHL under complex hydrodynamic condition is compared by developing mathematical model for Mumbai/JN port area. The model shows 95% and 90% agreement for water level & current respectively with the prototype. The effect of Mega Bridge, studied from hydro-morphodynamic considerations on existing waterfront facilities in Mumbai/JN port area is insignificant and may not hamper smooth functioning and as such is a sustainable development. Crown© 201 5Copyright The Authors. © 2015 Published Published by by Elsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015 Keywords:Estuary; Hydrodynamics; Harbour; Macro tides; Mega bridge; Unstructured Mesh 1. Introduction The various developing countries in Asia like China, Malaysia, South Korea, Singapore etc. are developing their infrastructural facilities at an exponential rate. The biggest democratic country in the world, India; is not an * Corresponding author. Tel.: +0-91-020-24103508; fax: +0-91-020-24381004. E-mail address: [email protected] 2214-241X Crown Copyright © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi: 10.1016/j.aqpro.2015.02.046 342 A.A. Purohit et al. / Aquatic Procedia 4 ( 2015 ) 341 – 348 exception to this and is also expanding its facilities almost at the same pace. These infrastructure developments are in the form of new road/rail networks, industries, townships, bridges, airports as well as major/minor ports to serve the need of waterborne transport in the country. Rapid modernisation and globalisation of the world in last few decades has necessitated India to carry out these infrastructural developments at speedy rate to fulfill the present requirements and cope up with the demands of future. In order to boost the economy, government has adopted policy of liberalisation and globalisation. Many private companies as well as joint venture organisations are coming up in the country to support Govt. policy of building power plants, minor port facilities, bridges, road networks etc. Waterborne transport facilities being the cheapest mode of transport, many coastal structures are being built in the country to explore the benefits of its resources. Presently, thirteen major ports and hundreds of minor ports are serving the country to cater the needs of waterborne transport. However, existing port facilities are not sufficient to cater future demands. In view of above, majority of new waterfront developments in the form of berths/jetties, docks etc. are being built either along the coastline or in estuarine/riverine areas. These developments require reclamations to stack material, bridges/approaches etc. Many townships are also being built in nearby area by reclaiming water area. Hence it is likely that it will alter the flow field at existing waterfront facilities, which may have adverse impact from hydro-morphodynamic consideration. Amongst the existing major ports in India, ports such as Mumbai, Jawaharlal Nehru (JN), Haldia, Kolkata and Kandla are natural/estuarine ports and are situated well inside the estuary/creek or are in the gulf region, while remaining ports are on open coast with breakwaters to achieve tranquility at berths for safe loading/unloading of ships. Mumbai and JN Ports are on West Coast of India and their locations in Arabian Sea are shown in Fig.1. Fig. 1. Location Plan of Mumbai & JN Port area Mumbai is a mega city of India and is not only the capital of Maharashtra state but also financial capital of the country. The city is well equipped with various infrastructures and connected to the rest of the country with transport facilities like rail/road networks and also to other countries with air and waterborne transport connectivity. Due to rapid industrialisation and Mumbai being traditionally the epicentre of India’s commerce, this narrow stretch of land (Mumbai Island) has seen a steady increase in population in the last three decades despite obvious spatial constraints. Hence, development of Navi Mumbai has been identified as an urgent requirement for easing pressure on the island city. Also many suburbs are being developed on the eastern side of Mumbai City in Thane, Panvel and Dharamtar creek areas either by various Governmental or Non-Governmental organisations. However lack of easy A.A. Purohit et al. / Aquatic Procedia 4 ( 2015 ) 341 – 348 343 connectivity to the mainland (Navi Mumbai), has stunted the growth and pressure on the island’s infrastructure continues to mount (2012). In order to cater the need of road traffic and avoid traffic Jams, Maharashtra Govt. has constructed number of flyovers in Mumbai city and still more are being built. However they are not sufficient and hence the problem of traffic jams right from Fort area in Mumbai up to Vashi city and beyond exists. All vehicles have to pass Sion/Chembur area to reach Vashi Bridge, which takes considerable time of about 2-3 hours during peak hours of traffic. Hence in order to connect the Island of Mumbai (west side) to main land (east side) there is a great need to have Mega Bridge (MTHL) crossing the entire Thane creek. The Government intends to provide a road and metro-link between Sewri on the island city of Mumbai with Chirle in Navi Mumbai on the mainland side, which passes through the harbour area of Mumbai & JN port as shown in Fig.2. Fig. 2. Location plan of proposed Mumbai Trans Harbour Link (MTHL) The peculiarity of Mumbai/JN harbour is that, it has ultra-wide estuarine entrance of about 10 km and it extends in Thane creek having water spread up to 30-40 km north. Also type of tide prevailing being macro semi-diurnal in nature with spring tidal range of about 5.0 m, large volume of tidal flux gets exchanged in and out of Thane creek during tidal cycle. This results in strong tide induced currents during flood/ebb tide and also significant sediment transport. The harbour areas of these ports are well protected from waves due to Salsette/Mumbai Island on the west and mainland on the east. The infrastructure developments in Navi Mumbai area are in the form of real estates, road/rail networks and waterfront structures in the form of Jetties, Wharfs etc. These developments are carried out mainly by reclaiming low lying areas. Major port like JN is also developing rapidly by planning a couple of kilometre long mega container terminal and reclamation in few hundred Hectares for stacking the containers. These developments will have some effect on siltation in the Harbour area. At present, the rate of siltation is not alarming, but it cannot be ignored also. Development of any facility/infrastructure may have detrimental effect on existing waterfront facilities and as such in order to have new development as a sustainable development, it is essential to study its impact on hydro- morphodynamics of entire harbour region. In Mumbai harbour tidal action is dominant than waves and it creates movement of large water mass to fill and empty the creeks, resulting in movement of sediment. Bed material in the harbour is very fine in nature and is brought in suspension by disturbance and is transported to and fro depending on direction and speed of tidal current. Tidal current plays an important role in transportation and redistribution of bed material within the harbour. In view of Mega Bridge (MTHL) being planned entirely crossing the Thane creek, wherein many piers are to be constructed; it may affect flow field and hence assessing effect of proposed development on existing waterfront structures in Thane creek from tidal hydrodynamic considerations is essential. 344 A.A. Purohit et al. / Aquatic Procedia 4 ( 2015 ) 341 – 348 2. Existing berthing Facilities in Mumbai harbour and Oceanographic phenomena The berthing facilities available in Thane/Panvel Creeks near Mumbai are mainly for berthing of either large container/crude/ bulk carriers, which are operated by Mumbai & JN Port Authorities. However, many small berthing facilities/waterfront structures in the form of wharfs, piled jetties, ferry terminals also exist in this region, which are owned either by private companies or government undertakings to cater the need of passenger transport or material handling.