Case Study

Project Summary CIDCO Facilitates Design of New Stormwater Project: ® Analyzing complex stormwater Systems With CivilStorm systems with holding ponds below high tide levels in an archipelago of Well-Planned Tidal-Water Drainage System Protects Archipelago Navi Project Location: From Flooding During Monsoon Season Dronagiri, , Maharashtra, India Drainage System Proposed Topographic Challenges Organization: City and Industrial Development City and Industrial Development Corporation (CIDCO) of Dronagiri is located near , one of In- Corporation (CIDCO) Ltd. Maharashtra, India, is a planning authority for the Navi dia’s largest and most modern seaports. It spans residential Be Inspired Awards Category: Mumbai area. It is responsible for the Dronagiri project, and industrial zones as well as a warehousing zone. The Innovation in Water, Wastewater, one of 14 new nodal townships in the previously undevel- 2,700-hectare township borders the Arabian Sea on the and Stormwater Networks oped Dronagiri archipelago. The region typically experienc- north, the Dronagiri Hills on the west, and Karanja Creek Project Objective: es heavy rainfall from August through November that floods on the south. Ensuring proper drainage of the the area completely. To prevent this flooding from occurring Topographic data revealed that 99 percent of the area Dronagiri area by building a storm- once the area is fully developed, CIDCO deployed Bentley’s proposed for development was below RL 3.00 meters and water network model of Dronagiri CivilStorm stormwater modeling and analysis software. from the catchment to the tidal the high tide level was 3.25 meters. The ridge lines of outfalls and calculating the roads CIDCO used CivilStorm to plan a drainage system of Dronagiri Hills indicated that the catchment would drain level and land development related interconnected channels that would discharge the runoff storm runoff into planned residential areas and a market to the project from high-intensity storms into holding ponds. These ponds that would be below high tide. CIDCO adopted the Dutch Software Used: would be equipped with flap gates and outlet structures Method of reclamation, which consists of holding ponds • CivilStorm that would enable them to hold the runoff under the worst and retention ponds, to provide a stormwater disposal tidal conditions. With CivilStorm, CIDCO was able to evalu- system and avoid flooding. It found this approach to be the ate the Dronagiri archipelago for overland flows in different most cost-effective. Fast Facts regions, examine the channels and holding ponds, simulate water levels in each holding pond under different storm and Technical Challenges • Holding ponds need to accumulate water during high tides and heavy tidal conditions, and check the adequacy of outlet pipes CIDCO authorities determined that the high tide in this precipitation, and allow flow back from the holding ponds. region occurred at RL (reduced levels) 3.25 meters and low into the sea at low tide • CIDCO authorities determined that the high tide in this region occurred at RL 3.25 meters and low tide at -0.75 meters • The 2,700-hectare township borders the Arabian Sea on the north, the Dronagiri Hills on the west, and Karanja Creek on the south • CivilStorm software served as an accurate decision support tool for designing the stormwater system

Figure 1: Dronagiri stormwater model shown in CivilStorm. The dynamic profile from Pond 1 to Pond 2 is displayed at Hour 11:30. “The CivilStorm tide at -0.75 meters. The water in the holding ponds would be discharged into the sea at low tide. But CIDCO needed a software helped way to create the computations to predict the water levels in different holding ponds at different times – for any given CIDCO design tide level as the rainfall progressed – for each revision of and analyze the land use plan. In addition, the holding ponds had to allow water to ac- the stormwater cumulate during high tides and heavy precipitation, and to infrastructure to allow flow back into the sea at low tide. Moreover, CIDCO had to consider road levels and surround- protect the Dronagiri ing terrain that were directly related to the holding ponds. Figure 2: Holding pond’s hydraulic grade Engineers also needed to know the land use development archipelago during “The CivilStorm model helped a lot during the planning stage plans to determine how much runoff would enter the ponds of the project to update the alignment and capacity of vari- and calculate their capacity (the runoff will vary depending monsoon season ous channels and holding ponds according to the changes on land use). once it is inhabited.” in land use development plans,” said P.R. Natesh, executive Holding Ponds Solution Using CivilStorm engineer, CIDCO. “The same work would have consumed Approximations of water levels using manual calcula- heavy manpower and time, and getting the results in the Find out about Bentley tions or Excel spreadsheets were required, but getting the desired formats would have been hard to achieve.” at: www.bentley.com results, which were often inaccurate, was time consuming. Environmental and Community Impact Using CivilStorm software for stormwater conveyance Contact Bentley The CivilStorm software helped CIDCO design and analyze 1-800-BENTLEY (1-800-236-8539) dynamic modeling, CIDCO’s engineers were able to the stormwater infrastructure to protect the Dronagiri Outside the US +1 610-458-5000 calculate thousands of iterations in a few seconds and archipelago during monsoon season once it is inhabited. Global Office Listings build a stormwater network model of Dronagiri from the Since the start of the project, CIDCO has developed basic www.bentley.com/contact catchment to the tidal outfalls. Because the modelers infrastructure in the zone, and around 350 hectares (20 were able to test various scenarios for the modifications percent of the land) have been sold. In addition, around 90 of the drainage systems to find out if they were adequate, hectares are currently being used for commercial purposes. the model simulated the effects of various changes in the planned drainage system. The software’s dynamic calcu- Natesh concluded: “Thanks to the efficient and timely use lations also served as an accurate support tool for crucial of CivilStorm, which ensured accurate dynamic calculations, decisions regarding the road levels and land development CIDCO was able to handle complex hydraulic problems, ensur- in Dronagiri. ing Dronagiri would be flood free to the best of its capacity.”

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