Last week the whole city was submerged after a rainfall that lasted only a few hours. Has anybody given it a thought that why the entire city got inundated during the recent rains. All this is due to the lack of public awareness and lack of civic sense among the people. The drainage system can never be designed for “Zero Submergence”. It’s beyond the design norms. As such there are some areas which come under submergence during heavy downpour due to their topography, but this phenomenon is purely temporary as the situation normalizes within few hours after the rains stop. It clearly indicates that there is no defect in the drainage system. This kind of phenomenon is observed in the metropolitan and cosmopolitan cities like Delhi, Mumbai, Kolkata & Chenai. However some submergences take a serious turn due to blockade of drains which is due to the users of the drainage system i.e. the population of that particular area. It has been observed that whatever the rubbish is generated in homes either in the form of faecal matter or polythene bags or any other organic or inorganic refuse, is dumped into the drains which every now and then result in the blockade of drains. Even the Green Sewer which has been designed for huge discharge and has a big enough section of waterway, gets choked occasionally and it requires to spend a considerable amount of money & manpower for removal of such blockades and making the drainage and sewerage system functional. Such situations can easily be avoided if the people in general become aware about their civic duties and the Government in particular takes stringent measures to stop such reckless use of drains. An important measure to be taken up is to impose a whole hearted ban on the use of polythene which has become an environmental hazard and being non-biodegradable often lead to chocking of drains thereby rendering drainage system non-functional. Also emphasis needs to be laid for the construction of a separate sewerage system in all the areas in order to meet the requirement of people on this account and to provide proper hygienic conditions. Moreover in order to avoid prolonged submergences it is essential to augment the existing dewatering stations in order to enhance their functionality due to increased demands also it will be necessary to replace the worn out machinery at these pump stations.
Before discussing the present scenario of drainage system in the Srinagar city in particular and that of the valley in general, we must understand the function of a drainage system and differentiate it from that of a sewerage system. The essential principle of any type of land drainage is to provide an open, adequate, and readily accessible channel through which the surface or subsoil water can flow. For this purpose open ditches are sometimes used, but these are not always satisfactory because they may become choked with sediment and vegetation. Underground drains are thus usually employed to overcome this problem.
Drainage means removal of surface or subsurface water from a given area by natural or artificial means. The term is commonly applied to the removal of excess water by canals, drains, ditches, culverts, and other structures designed to collect and transport water either by gravity or by pumping. A drainage project may involve large-scale reclamation and protection of marshes, underwater lands, or lands subject to frequent flooding. Such a project usually involves a system of drainage ditches and dikes; often pumps are required to raise the water into the drainage network.
In cases of large-scale drainage it is essential to improve the discharge capacity of natural channels to protect adjacent properties and to upgrade the ditches and channels that convey the runoff from drainage systems to the improved channels. Such connecting drains commonly follow the natural surface drainage pattern of the area, intercepting the normal surface runoff that takes place during periods of excessive rainfall.
In draining comparatively flat land, common practice is to lay along one side of the plot a main drain to which a number of transverse laterals are connected. The laterals are often set parallel to the main drain, coming together to join it at the lower end of the field. Local conditions of soil and terrain govern the spacing of laterals and the depth at which they are placed. To prevent water from higher ground from reaching lower areas, catchment or interception drains are frequently built. They consist of ditches or underground drains, placed across the slope, that catch water and carry it away before it reaches the low ground.
The drainage in the Srinagar city poses a particular problem, since parts of the city are lower than the river and adjacent lake area thus to drain out the area, the system needs to be provided with the dewatering stations having effective and adequate pumping equipment with proper backup in order to meet the power failure which is frequently experienced in the valley. The drainage system constructed already in the city of Srinagar envisaged the disposal of drainage water in to the natural drainage channels & wetlands identified by the flood control department for the purpose. The disposal of the drainage water thus has to be into the natural drainage channels or wet lands as is done in many other countries and even in United States. Where gravity flow is impossible, the water from the drainage system is pumped away into streams or canals, the level of which is often higher than that of the drained land.
Though, as reported in the news item, it is a fact that only 20-30% of the city is covered by the drainage system, yet it is far from reality that the drainage system where it exists is inadequate being constructed during Bakshi era. The drainage system of any area is designed on the basis of catchment area of that particular system with an assumption of a rainfall intensity of 8-10mm per hour taking appropriate runoff coefficient depending upon the topography of the area. Since the land use at most of places has changed in the city outskirts the runoff coefficient adopted for designing any drainage system is likely to change thus there always remains scope for up gradation of the drainage system. However it does not hold good for the city centre area such as the area from Tagore Hall to Kaka Saria including HSH Street Sahheed Gunj etc and from Maulana Azad Bridge to Budshah chowk including Residency Road and Lal chowk, as the topography of this area has not changed much since the construction of drainage system in this area. The area has an effective drainage system with sufficient number of dewatering stations and network of drains sufficient enough to cater to the surface runoff for which it has been designed.
Then what went wrong that entire city came under submergence and remained water logged for hours together which created panic among the business community and the inhabitants of these areas? All this is experienced due to choking of drains and large scale siltation of the drainage system which has reduced the carrying capacity of these drains. During the devastating deluge of the city in September 2014, the water remains stagnant in most of the area for more than twenty five days and the entire silt load transported by the flood water from the mountainous region got accumulated in the drains thereby rendering the entire drainage system dysfunctional which resulted in the inundation of city due to rain water on 29/03/2015. and many times thereafter including on 24/07/2019 the drainage system been rehabilitated and cleaned properly by way of de-silting of the network of the drains and if the worn out and damaged machinery during floods been replaced the storm water of the rains on would not have worried the populace as the entire storm water could have been discharged into the outfalls through the effective network of drains.
After the devolution of municipal functions to Municipal Corporation, Urban Environmental Engineering Department has been reduced to one Sewerage Division in Srinagar and one Sewerage Sub Division in Jammu. The other Divisions which were taking care of the Drainage sector have since been given under the Administrative control of either the Municipal corporations or urban local bodies of Srinagar and Jammu Divisions. However some areas like Buchwara and Khanyar which were previously looked after by the Drainage Divisions were transferred to the Sewerage Sector. Since no sewerage system existed in these areas, the existing Drains are being used as sewers. As indicated earlier these drains transport with them a huge amount of trash which not only overloads the only existing treatment plant but also results in the frequent blockades in the trunk sewers in which these drains culminate. Though the drainage and the sewerage system have different functions to perform yet it has been observed that both the Drainage and the sewerage system of the city perform same functions, otherwise the drainage system meant for taking care of the storm water would have been dry during the dry weather and the sewerage system meant to take care of the sewage would not overflow during the rains. The ground reality is that the area under the administrative control of UEED is named as Sewerage and that under the administrative control of Municipal Corporations is given the name as drainage though both the systems perform identically the only difference is that the discharge taken care of by UEED is first taken to STP Brari Numbal for treatment which makes the treatment plant overloaded owing to its capacity for treating Sewage flow only. As a result, there is always a dual control on the drainage as well as sewerage system.
To overcome this problem, there seems to be only solution and that is to provide a separate sewerage system so that the people open the house connections into the sewers in order to dispose the night soil and kitchen waste which contains the chemicals due to excessive use of soap. The sewage needs to be treated before its disposal into water bodies. It needs to be borne in mind that the urbanization has had profound effect on aquatic environment of the city of Srinagar. During urban development vegetation is removed and replaced by roads, car parks, drive ways and roof tops that are impervious to rainfall. Unable to percolate into soil, rainfall becomes completely converted into runoff. Furthermore the impermeable surfaces associated with urban development are often contaminated by a variety of gross pollutants such as detergents, trace metals, hydrocarbons, nutrients, pesticides and herbicides. Due to the topography of the vale of Kashmir in general and that of Srinagar city in particular the storm water while flowing down the streets or the road on its way picks up gross pollutants like dirt lawn clippings, pet waste, salt, lawn chemicals, field fertilizers, oil grease etc. This water and the pollution load it carries generally go into the storm water drains of the area and from there to the nearest stream, river or the water bodies without treatment. Studies have determined that up to 70% of our surface pollution is carried along by the storm water. This pollution load not only results in the siltation of these water bodies but also cause the eutrophication of the water quality of these water bodies. Thus keeping in view this fact the concept of discharging the storm water discharge directly into the water bodies without any treatment is mediocre and thus not perceptible.
The concept of a separate system for the storm water drainage keeping in view the huge operational cost of the treatment plants, can prove a success only if both the system i.e. Drainage system and the Sewerage system coexist so that the storm water, grey water and the black water is taken care of simultaneously. Otherwise as experienced form the present scenario of the existing utilities on this account the sewerage system is being used as drainage system as well which results in its overloading of sewers and treatment plant and thus the desired results are not achieved. Similarly where sewerage system does not exist, the existing drains are being used for the disposal of sewage as well and since the drainage discharge is disposed in existing water bodies without treatment, it results in large scale eutrophication of these water bodies thereby making their condition abominable.
In most of the areas topography does not permit a separate system thus in these areas it will not be possible to segregate sewage from the storm water/drainage owing to the congested population and closely built houses, narrow lanes and by-lanes. As indicated earlier the city of Srinagar has observed a yawning sprawl in its limits and a number of new colonies have come up in an unscientific and haphazard manner. The service roads in these colonies are so narrow and do not have sufficient width to accommodate the basic utilities like water supply distribution pipes, electric poles, telephone cables etc. thus it will not be possible in these colonies to have a separate system as the width of these lanes and by lanes do not permit to lay sewers as well as drains separately. To overcome this problem it is suggested to convert the existing drainage system where ever it exists into the combined system as the dry weather flow is almost negligible as compared to the storm water flow and can always be taken care of by the storm water drains. This can be achieved by employing the technique of Trench less rehabilitation of existing system. This technique is the modern technique and has many advantages. Also it is suggested to adopt a combined system in all existing colonies which have come up in unscientific way. However in new areas which shall be strictly developed on scientific grounds, separate system can be adopted.
This can be achieved by making for the people at helm accountable and for which the Environmental Engineering Department (UEED) needs to be revived for the effective management of sewerage and drainage system which needs to reverse the decision of transferring drainage Divisions both civil and Mechanical into the control of Srinagar Municipal Corporation after devolution of municipal functions. Thereby transferring these Drainage Divisions both Civil and Mechanical back under the administrative control Urban Environmental Engineering Department (UEED) after reorganizing the Department as there is need of one Sewerage and Drainage Division in every District keeping in view the urban agglomeration.
1. Urban Environmental Engineering Department (UEED) needs to be restored to pre devolution position of 2005 by way of immediate transfer of Drainage Divisions both Civil and Mechanical in Srinagr and Jammu to Urban Environmental Engineering Department with the creation of one new drainage and sewerage Division in each District.
2. Topography of the entire area for which the drainage system is being proposed need to be surveyed, its slope and terrain need to be accurately mapped by using latest mapping technologies.
3. Available hydraulic head in the system up to highest flood level of the river or water body which will serve as disposal need to be established.
4. Geotechnical survey of the area need to be conducted so that the details of ground water depth and its seasonal fluctuations affecting construction of the drainage system form infiltration, and structural design (uplift considerations) point of view are established. Also the soil bearing capacity and type of soil strata expected to be met during construction need to be evaluated for each basin /area. The concept report lacks this part. It is, thus suggested that the consultants should conduct the geotechnical surveys and incorporate this part in the final DPR and all the structures should be designed in accordance with these survey reports.
5. In order to ameliorate the situation and to reprieve the public from the sordid atmosphere due to water logging, the existing drainage net work needs to be extended to all the new colonies with proper dewatering stations where ever required with the pumping equipment of fuller capacity and sufficient enough to cater the design discharge of these areas. Consultants should as such include the grey water content while calculating the design discharge.
6. The existing system needs to be revamped by way rehabilitating the damaged/non-functional portion of the system. Moreover The sewer appurtenances such as manholes, lamp holes, street inlets, catch basins, flushing tanks, storm-relief chambers, grease- traps etc should be proposed to be introduced at required place in the existing system, proposed to be rehabilitated as the present system lacks these devices which are otherwise necessary to assist in the efficient operation of the system.
7. The worn out machinery need to be replaced in all the existing dewatering stations wherever required. Also the existing under capacity dewatering stations need to be augmented by supplementing them with the additional pumping equipment. All the dewatering stations need to be fed from the essential service feeder of the power supply for their uninterrupted functioning. Also arrangements need to be made for the backup in case of power failure which is frequently observed in the valley. Such provisions need to be incorporated in the project cost.
8. Since the storm water and both black water and the grey water need to be treated before their discharge into the water bodies in absence of the separate system for Drainage and sewerage, it will be expedient to have a combined system with CSO mechanism for its treatment in order to reduce the operational cost of the treatment plants during the heavy downpours/Storms. It will be important to mention here that as per the available rainfall data it has been observed that the Srinagar city experiences 55 numbers of rainy days on an average during the year. This implies that for more than ten months of the year the combined system will carry dry weather flow only. For rest of period the storm water combined with the waste water will be regulated to a combined treatment facility. This method will not overload the dry weather treatment facility which will have to work for about ten months of the year thus saving energy and running cost.
9. As the storm water and the grey water need minor treatment and break more quickly than the black water, Possibility of adopting sustainable drainage system need to be explored where ever wherever applicable in order to reduce the number of conventional treatment plants and thus the operational cost on account of treatment of the drainage discharge.
10. Wherever possible construction of retention basins and detention basins need to be proposed to remove the pollutant load from the drainage discharge before its disposal into water bodies in order to avoid eutrophication and siltation of these water bodies.
11. The sewage collection (House connections) should be made through the closed pipes instead of open surface drains to avoid entry of garbage into the sewer lines which otherwise may result in the blockade of the sewers.
12. As far as possible all proposed drains need to be kept covered with RCC slab to avoid their misuse by way of dumping garbage and other household waste into these drains as has been observed commonly. This will also keep the drainage system in a better state of hygiene.
13. All designs shall have to be in accordance with the norms as laid down in the manual of sewerage and sewerage treatment prepared by Central Public Health and Environment Engineering Organization (CPHEEO).
(Er. Mehraj -u- Din Bhat is Executive Engineerster Water Supply Mas Plan Division Srinagar