Design of Stormwater Drainage System Using Geomatics and Haestad Method : A Case of Gandhinagar City

Abstract

India's rapid economic growth in the last two decades has been accom- panied by increased levels of urbanization. This transition will make India's urban population close to 600 million by 2031 (i.e. 38% of total popula- tion from 27% of present population). Various reports also suggest that 70 percent of net new employment will be generated in cities. 91 million ur- ban households will be middle class, up from 22 million today (McKinsey Global Institute India's urban awakening: Building inclusive cities, sustain- ing economic growth). Above gures signi es that the urban sector will play a critical role in the structural transformation of the Indian economy and in sustaining the high rates of economic growth in coming decades. It becomes essential to ensure high quality public services for all the cities and towns of India so that it can facilitate the full realization of India's economic poten- tial and excellent quality of life to urban dwellers. India's economic growth momentum cannot be sustained if urbanization is not actively facilitated by basic infrastructure such as water supply, sewerage and sanitation facilities, roads and storm drains etc. Currently, the basic infrastructure facilities in Indian cities have not kept pace with the burgeoning population and physi- cal sprawl. They are visibly de cient in the quality of services they provide, even to the existing population. Only about 63 percentage of the urban population has access to sewerage and sanitation facilities as on 31 March 2004 (Eleventh ve year plan). Considering that there is an urgent need to strengthen basic infrastructure such as drinking water, sewerage, solid waste management, roads and storm drain of our cities. Government is playing its part to give basic infrastructure to cities by imple- menting various schemes (JNNURM is part of that initiative). The invest- ment for urban infrastructure over the 20-year period is estimated at Rs 39.2 lakh crore at 2009-10 prices. Of this, Sectors delivering urban services such as water supply, sewerage, solid waste management, and storm water drains will need Rs 8 lakh crore (or 20 per cent). It is estimated that Rs. 1.92 lakh crore rupees will be require to strengthen stormwater drain in all cities in India by 2032. [1]. As part of the ongoing endeavor to facilitate critical reforms in the urban sector, the Ministry of Urban Development has now adopted National Benchmarks in four key sectors-Water Supply, Sewerage, Solid Waste Management and Storm Water Drainage to monitor progress of basic infrastructure in various cities of India [2]. According to that, Coverage of storm water drainage network should be 100 percentage in all cities and no Incidence of water logging or ooding should be there. There are very few cities which have such kind of stormwater drainage systems built into their most basic structure. In Eleventh Five Year plan, Rs. 1,29,237 crore were al- located to strengthen urban basic services. Indian urban local bodies (ULBs) also need to get strengthened as local self-government with clear functions, independent nancial resources, and autonomy to take decisions on invest- ment and service delivery to make implementation process more e cient. They must also be made accountable to citizens (Report on Indian urban infrastructure and services). Above Elements has been taken into considera- tion in the 74th Constitutional Amendment, the Jawaharlal Nehru National Urban Renewal Mission (JNNURM), and the emphasis placed on the urban sector by the Thirteenth Central Finance Commission. ULBs are executing various schemes of central and state government to strengthen stormwater drainage system in their cities and towns It is necessary to understand various features of Stormwater drainage (SWD) system. SWD system is managed by installing a system of inlets and outlets, connected by a series of pipes. Lack of proper SWD system causes great inconvenience to public in terms of tra c congestion, route blockage and water diseases due water logging. It is typically designed to carry runo away from areas where it is unwanted (such as parking lots and roadways), and the design discharge is generally accomplished by the application of ra- tional method with the use of segregated database and excel spread sheets. This approach of design has certain limitations and not able to give properly optimized solution to our problem of stormwater drainage (100 percentage coverage and 0 incident of waterlogging). This system seems under-designed during peak events in monsoon but simultaneously looks not maintained during other seasons. There are various reasons behind this ooding such as improper slope or improper de nition of catchment area. It is caused by consultants limitation to design this system for one return period and not to consider any sensitivity analysis which is compulsion to check behavior of system during various rainfall events. They also don't consider future changes in land-use and other emergency situation respond scheme. The main reason behind consultants not doing is that SWD analysis is be- ing done in excel sheets using segregated database which makes process very lengthy and cumbersome because it involves much iteration process. These process plus segregated database don't allow us to experiment our design for various return period and scenarios. This problem can be overcome if we can prepare integrated database to reduce redundancy in data but e ciency in data handling as it will make analysis process much faster. Geomatics help us in creating integrated Geodatabase for SWD system which can be further integrated with Stormwater drainage design software to give us much possibility in design process. In this dissertation work , attempts has been made to integrated Geomatics and Haestad method to make design process more meaningful. It is possible to carry out sensitivity analysis and run model for various scenarios for identifying optimized design using Geo- matics and Haestad method. Gandhinagar- A capital city of Gujarat state, has been taken as study area which gets ooded every year during monsoon due to inadequate drainage system. This causes great inconvenience to the tra c, neighborhood resi- dents and damage to asphalt roads. Therefore it is essential to have a ef- cient system for disposal of the storm. State government has taken many initiative but they seems inadequate as this situation is continuously prevail- ing in many areas of both city. There is urgent need to update storm water system in Gandhinagar. In this dissertation work, integrated geodatabase was developed for SWD sys- tem with GPS survey of entire Gandhinagar city and various layer creations for contours for extracting general slope of the city, catchment de nition, land-use analysis, area calculation, primary layout. Developed geodatabase with rainfall analysis (I-D-F curve using extreme value analysis) was used to design SWD in StormCAD for sector-5 of Gandhinagar city. Later, Sensi- tivity analysis of SWD system for various return-periods (i.e. 5, 10 and 25 years) and their cost comparisons was executed. Project inventory in terms of pipe requirement of various diameters was prepared. Total calculated cost (excluding xed parameters) of 5, 10 and 25 year return period design ex- ecution came out to be Rs. 66.28 lacs, Rs. 97.28 lacs and Rs. 1.10 crore respectively. It has been observed that Geomatics with Haestad software can help in identifying most optimized design for SWD system. Further, sensi- tivity analysis and model building capability of this technology strengthen our design capability.