 Namaste and welcome back to the video course on Watershed Management. In module number 8, lecture number 32, we will discuss today urban drainage system. So, some of the important topics covered in this lecture includes urban flooding, disaster risk management, urban drainage system, design requirements, roadside drainage design. Some of the keywords for today's lecture urban flooding, drainage system design, risk management and roadside drain. So, as we were discussing earlier, so when we discuss about watershed management, so we are taking it as a holistic way. So, we have to see the urban areas also and then we have to see the storm water management within the watersheds and then we have to see the say later flooding and overall say the storm water management within the system. So, as we discussed in the last lecture, say the storm water system we have to we can design as separate system or combined system and then say whenever the urbanization takes place there is lot of changes to the to the watershed and the time of concentration reduces and the peak to the hydrograph, the peak of the hydrograph increases. So, like that a number of hydrological changes takes place with respect to the runoff taking place within the watershed due to the urbanization. So, due to all this as we discussed there is good chance of say increase the chance of flooding within the watershed. So, that way we have to we should appropriate flood management say planning as far as the watershed is concerned. So, somehow the the the causes of urban flooding say here I have mentioned. So, it can be as we discussed a large increase in concrete or impervious surfaces or unplanned usage of urban lands or lack of proper drainage or loss of wetlands or it can be less ground water usage or recharge, tidal effects or very heavy storms or cloud cloud burst or say like a climate change effect. So, there can be number of such causes as far as urban flooding is concerned. So, say lot of changes takes place due to the urbanization to the considered watershed. So, that way the impervious surface area increases and then wetlands will be lost many locations and then if there is no sufficient drainage or the drainage is not proper then the chances of flooding increases. So, that way we can see that in most of the urbanized watershed say there is problems of flooding. So, the problems of flooding are increasing and then we have to we should appropriate plans when we deal with the watershed management. So, now let us look into what are the things which we can do to deal with these kinds of urban flooding say on a watershed basis. So, in this slide some of the important points related to urban flood disastrous management are mentioned. So, as we discussed say to deal with these kinds of urban flooding we have to develop appropriate coping strategies and disaster reduction plans along with the greater awareness of how to reduce risk. So, that is the high priority as far as watershed development and plan circumstances. So, there can be number of strategies. So, strategies like we can go for enhanced national stage and local scale advocacy partnerships and knowledge management. So, we can get to say all the data and then come up with certain decision support systems which can say clearly say that what are the possible ways to reduce the flood say urban flooding. And then standardizing hazard risk management tools so, we can say come up with some standard management tools and methodologies and practices to reduce the risk of urban flooding. Then developing integrated and coordinated approaches so, same as far as the flooding is concerned say as we discussed in the previous lecture also it is not only simply the storm water drainage which we have to manage, but we should have look into holistic same watershed management including LID schemes or low infrastructure developments or the integrated storm water management schemes. So, like that as we discussed in the previous lecture. So, that way we have to standardize the management tools and then we can have a we can develop integrated and coordinated approaches. And then also we can incorporate learning by doing mode of operations. So, we can see that in many cities say there may be number of floods that happens earlier times. So, from that we can learn a number of lessons. Say for example, in Mumbai and July 26 2005 there was a severe flooding. So, from that we can learn many lessons and then we can implement many changes many things to the to the area considered so, that to this flood risk can be reduced. So, that way this the learning by doing mode of operations are very helpful. Then we can promote the diffusion or the documentation of best practices. So, as we discussed in the previous lecture also so, there are a number of best practices are possible. So, we can say say come up with specific documents say how we can reduce the risk as far as the urban flood flood is concerned. So, that we can go for better management practices and then this can be say communicated to various the stakeholders in going common public schools and public enterprises or the private institutions. And then also we can build appropriate communication protocols facilitating multi-platform and multilingual dissemination. So, as far as flooding is concerned say if there is any area say due to heavy rainfall or any other reason if there is an area which is flood prone then we need to have appropriate communication protocols we can develop and then the people can be want say just like advanced flood warning systems and that will be very useful to the to reduce the risk as far as the urban flood is concerned. So, whenever deal whenever we talk about the disaster risk management as far as urban flooding is concerned we have to come up with appropriate plans and then we have to come up with appropriate guidelines with previous experiences and then also we have to disseminate this information to the stakeholders and various agencies. So, that the appropriate flood warning system can be made and so, people lives and money can be saved this way. So, that way when we discuss about the urban flood disaster risk management say we have to analyze and present information in an easily understandable form for wider use by decision makers. So, whatever we are making as far as the guidelines or as far as the management plans so, it should be analyzed and presented in such a way that it is easily understandable to the decision makers or the politicians or the district authorities like that. And then we have we can encourage integrated approaches of projective mitigation based on master plan. So, each urban urbanized watershed is concerned we can come up with certain master plans and then we can have integrated approaches as far as the projective mitigation is concerned. So, that the flood risk can be reduced and then also we can encourage states to accord top priority to deal with recurring urban flooding. Say for example, government of India say as central government so, government of India can encourage states governments to give top priority as far as to deal with the urban flooding. Since when urban flooding happens say the economical loss will be very high the human loss will be very high. So, that way we should have integrated flood risk assessment plans and we have to go for disaster risk management as far as the urban flooding is concerned. So, whenever we deal with the urban flooding number of difficulties are there. So, some of the difficulties I have listed here like a comprehensive risk assessment then factoring risk in development planning coordination among different institutions lack of information sharing disintegrated investment decisions lack of consultation with stakeholders etcetera. So, like that when we look into urban flood management like whenever we look into disaster risk management say number of problems are there. So, say most of time number of agencies will be working as far as the urban flood risk assessment and management is concerned. So, we have to coordinate these agencies and then most of the time the stakeholders those who are affected by these floods they will not have sufficient information. So, we have to consult with them and then we have to disseminate the knowledge and then we have to we should have comprehensive risk assessment plan covering all the aspects with respect to the master plans as far as the urbanized water shed is concerned for the disaster risk management. So, now say we were discussing say when we deal with the urban flooding say it is always better to deal with on a water shed scale or on a catchment scale. So, that is hydrological unit is considered in the in the plans as far as the urban flooding is concerned. So, now let us discuss the urban flood management within the perspective of water shed management. So, as we discussed any planning for effective urban flood management has to take into the consideration of entire water shed. So, since a water shed is defined in such a way that it is hydrological unit wherever the we can have a single outlet where the all the runoff will be coming through a single outlet. So, that way the water shed is the best unit to look into the urban flood management. So, then that way on water shed basis we can identify the problems, causes and we can go for various remedial measures. And then also on water shed basis we can go for the preparedness and then mitigation as far as the flooding is concerned what kind of mitigation measures to be undertaken. And then also since a water shed is a hydrologic unit. So, when we look into early warning system and then communication it is always better to be on water shed basis. And then the response action also it is better to be on water shed basis since the response is concerned it is with respect to deal with the discharges taking place within a water shed or the depth of flow taking place. And then also we can go for awareness generation within the various stakeholders and that way we can develop the community capacity to deal with such kind of flood problems. And then also we can develop vulnerability maps and then risk assessment maps. So, that the total the risk or the vulnerability due to the urban flooding can be reduced very much. So, that way like a hazard mapping or flood level mapping and then we can identify the damages and then as a if any specific locations are there then we can go for insurance and risk transfer. So, that way various things are possible when we deal with the urban flood management on a water shed basis. So, it is not just like an administrative unit just like a district or a taluk or a village, but it is always better to go on a water shed basis as far as urban flood management is concerned. So, that way when we deal with the urban flood management on a water shed basis if we can develop a special decision support system which we discussed in one of the earlier lecture. So, we can develop appropriate special decision support system which we can show say the vulnerability to flooding or say the flood risk areas and then we can easily predict which of the area will be affected whenever say the water level raises to a certain level. And then so that way the decision makers can easily understand what will be happening due to say certain specified intensity of rainfall or the predicted rainfall. So, that appropriate measures management measures can be taken to save lives or to save properties. So, that way we can have an urban information system say for example, in Mumbai city after the 26th July 2005 rainfall say disaster management cell has been opened and then this cell is monitoring say with respect to the during the monsoon season how the very rainfall pattern changes or with respect to heavy rainfall what are the possibilities of flooding or what are the which are the areas which may be affected due to flooding. So, that way this disaster management cell gives information to the public media and that will be disseminated and then that way we can have appropriate managing plans. So, that way it is always better to develop an urban information system so that we can come up with appropriate plans to deal with the urban flooding problems. So, now whatever we have discussed is say the urban flooding and related courses and then what are the risk involved and then how we can manage. So, now let us discuss about the urban drainage system since drainage pattern or appropriate drainage is given then to a bigger stance the urban flooding can be reduced. So, appropriate urban drainage system is very important as far as the urban management is concerned. So, urban drainage system so drainage system generally we can categorized into major drainage systems and minor drainage systems. So, major drainage systems generally say to this comprises of open NALAs or streams and channels and natural surface drain. So, say whenever rainfall takes place in the urbanized area then this the immediately the runoff starts especially from the interior surfaces and this will be collected through minor drainage systems just like a network of underground pipes and channels. So, that is so called a minor systems and this minor system will be joining the major drainage systems just like streams, NALAs say small channels or rivers. So, this finally it will be taken to larger wells or the to the ocean directly depending upon the area. So, minor system generally we can categorize into two types like a separate and combined storm water drainage system. So, this also we have discussed in the last lecture. So, in the separate drainage system generally there is one system to convey the the storm water and another system to convey the sewage or the say as a separate sanitary sewage. So, the sanitary sewage usually underground pipes convey the wastewater from homes and business to discharge point while the storm drains which is the underground pipes or channels collect the storm water from the rainfall runoff and convey to the discharge point. So, depending upon the city or depending upon the location there may be separate systems or the combined system. So, the advantage and limitations of separate system and combined system we have discussed earlier. So, as far as urban drainage system is concerned there can be major drainage systems or the minor drainage system. So, when we look into the urban drainage processes so, we can put it in a flowchart like this. So, the the urban runoff is coming from precipitation or snow say precipitation as rain or snow and then if you consider the watershed area there some area will be same pervious area and some area will be say urbanized or impervious area. So, we should have a say using hydrologic models so, we can model this rainfall runoff by considering various processes like evaporation, infiltration, overland flow like that and then say by by using hydrologic models we can get the hydrographs so, which is the say overland flow as far as the considered hydraulic unit is concerned and then this the hydrographs which we consider that will be further this overland flow will be joined to the channels or the big drains or small drains depending upon the conditions and this say we can model through hydraulic models. So, we can be either say the the flow through on the roads or say pipe flow and so, that can be various say there can be some storage as far as road is concerned or this we were to routes and then most of time we have to identify how much will be the depth of flow and how much is their discharge passing or flooding taking place and then of course as far as the main roads are concerned number of opportunities will be there roads and drains will be there and then say the culverts will be there then inlet will be there. So, like that number of opportunities will be there roads and opportunities will be there. So, this overland flow will be passed through the the road to this to the opportunities to the major drains like drain channel or pipe and then that will be routed as drain flow and that will be the discharge which is coming to a major channel stream or river and that will be further routed. So, that way when we discuss with the urban drainage processes. So, we have to say deal with the hydrological aspects and the hydraulic aspects. So, had we we need to have a hydrological models so, which converts the precipitation to runoff. So, that can be mainly for overland flow conditions and then we should have hydraulic models which will be routing this runoff through the roads through the roadside drains through various opportunities and then through drainage channels or pipes and to the to the main drainage system or the main mahala or the streams or river. So, that is the way we have to model the urban drainage system say starting from the precipitation to the runoff to the main river or channel say through various say overland flow conditions or roads road flow on the road or the small drains pipes like that. So, this flow chart shows a typical hydraulic process as far as urban hydrology is concerned. So, now let us look into various aspects as far as stormwater drainage system is concerned. So, as we discussed say this total stormwater system can be major stormwater system or minor stormwater system major system include the small channels, mahalas and rivers minor mainly consist pipe drains or small drains open down drains. So, we should have an inventory of all this drainage system within the area which we consider. So, most of the time we can do this through a GIS platform. So, that we can identify the locations easily where is the major drainage system where are the minor systems so, like that. So, we can we should have an inventory so, as far as with respect to the watershed to enable proper hydrologic and hydraulic analysis and what so, what are say particular local locality based to enable coordinated administrative management. So, most of time administration is concerned it is administrative area will not be most of time the watershed based. So, that way say many of this local administration have to coordinate together. So, it is always better to have an inventory of the drainage system the major drainage system as well as the minor drainage system. So, as far as minor drainage systems concerned we should map this minor drainage systems clearly showing the interconnections with the major systems besides the cross connection with the sewer lines. So, say if there is any cross connection with the sewer lines for the minor storm water drainage system that should be also clearly shown and all the interconnections should be shown and then where this minor systems join the major systems also should be clearly shown. And then as far as major system is concerned we should map clearly with delineation demarcation and details of cross sections then slopes drain crossings including natural formations and manmade structures. So, all this say we should have appropriate inventory within a GIS platform. So, that say whenever we are having a flooding warning systems a flood warning system which a flooding. So, that we can easily identify which area will be flooded and what kind of appropriate measures to be taken so that we can save lives and property. So, that when appropriate inventory in a GIS platform helps to reduce the flood related problems. So, now let us look so we were discussing about the urban drainage systems. So, whenever we are going to design an appropriate urban drainage design say we have to meet with certain requirements. So, let us look into various aspects as far as the urban drainage design requirements are concerned. So, the development of an adequate and functioning drainage system based on sound hydrologic and hydrologic design principle we should have. So, we have to see the hydrologic principles. So, like rain fart runoff and then how the flood routing all takes place so that we have to get through a hydraulic design. Then design of an urban drainage system requires knowledge of the catchment area and topography, then urbanization details rainfall intensity, hydrology, hydrologics etcetera. So, the number of factors number of things we have to consider when we go for urban drainage designs like the catchment area its topography, then the rainfall details, then the hydrologics details etcetera. Then as we discussed most of the time it is always better to go for watershed or catchment as basis as far as urban drainage design is concerned. So, that way we should have the conduces of the watershed so that we can easily determine the boundaries of the watershed or the catchments for computing the directions of flow. So, as we discussed earlier based upon the conduces and then the topography details we can come up with a digital elevation model. So, this digital elevation model as shown here that indicates the flow directions and then how the if a flood type space how it will be affecting the watershed. Then say as far as rainfall is concerned another important data. So, for design of a drainage system the conventional practice is to choose an appropriate statistically relevant design storm to establish the storm water flows to be conveyed based on existing national and international practices. So, certain codes are there Indian standard codes or international standard codes. So, accordingly we should consider say how much rainfall intensity or intensity duration frequency curve say for example, depending upon the importance of the areas just like airport we need a say maximum consideration or say roads or say specified installations. So, like that we have to consider. Then we can also come up with the design storms which are generally estimated from rainfall data records for a long time and then we can come up with the intensity duration frequency curves. So, which shows the relationships between the rainfall intensity and then its possibility of occurrence. And this idea of curves need to be used to maintain design standards for new systems and then also retrofitting and replacement of all the urban drainage systems. So, that way say we have to keep on updating the idea of curves and then come up with the appropriate rainfall intensity while designing the new urban drainage systems or when we are going for retrofitting or replacement. So, idea of curves should be developed for each city based on extraction of data from the road data charts and this can be say minimum 15 minutes resolutions. So, that we can easily identify which are the locations of possible locations of flooding or what kind of say how the discharge or the flow depth will be varying within the watershed which we consider. So, now let us look into some of the important design consideration as far as urban drainage is concerned. So, some of the important say considerations like a frequency of thunderstorms. So, we should also look into additional considerations for planning future urban drainage systems and then as far as say discharge flow or design flow is concerned to protect urban areas safe management and passage of water resulting from frequent storm events like say we have to look into hydrologic design and then corresponding hydrologic design. So, we have there should be adequate capacity as far as the drainage system is concerned. So, we have to consider this design flow. Then urban drainage design most of the time our main objectives include hydrologic analysis and design to estimate the peak flow rates and the flow hydrograph for the adequate sizing and design of conveyance and quantity of control facilities. So, as I mentioned earlier we had two components one is a hydraulic design, second one is the hydraulic design. So, accordingly say the main objective is to do a hydrologic analysis and design. So, that gives the peak flow rate time to peak and all those details and then accordingly we design the drainage section and then its conveyance and then the control facilities as far as the flood movement is concerned. So, to estimate the peak flow rates say the nuance of the rainfall intensity is duration and frequency is required. So, this we can consider the historical rainfall events say for example, at least 10 years and you always say always if you can have more data like 50 years or 100 years of data we can analyze and then come up with say appropriate levels of say as far as design flow is concerned depending upon the area which we consider. Then say when we look into urban drainage design say we have to deal with the number of problems. So, like say some of the important problems are listed here like increase in rainfall intensities. So, in the last few decades you can see that many cities like Mumbai, Kolkata, then Chennai etcetera are affected by high intensity short duration rainfalls and this rainfall causes heavy flooding and large losses as far as the human life and property are consensed. So, this can be due to various reasons like cloud burst or the urban heat islands problems or climate change impacts. So, that way we have to deal with increasing rainfall intensities induced by climate change, urban heat islands or other factors which will possibly result in varying return periods for a given intensity of rainfall. And then rainfall intensity to be used for design will also depend upon the time of concentration. We have to identify how much is the time of concentration as far as the considered water shade by considering the various parameters and then if higher the catchment area higher will be the time of concentration and lower will be the design rainfall intensity. Other factors remaining the same, but we have also how to see the effects like a tidal effects say for example, in cities like Costa cities like Mumbai or Chennai are affected by the tidal effects also. So, we have to see simultaneously not only related to the rainfall runoff pattern, but also the tidal effects. As far as peak flow rates are considered we can simply use methods like rational method which is q is equal to c into i into a where a is the area of the catchment, i is the intensity of rainfall, c is the coefficient of runoff. So, this is this symbol formula we can utilize for hydrologic analysis. And then say we can say as far as this rational formula is concerned approximations based on runoff coefficient and rainfall intensity and area of catchment. So, that way we can easily do calculations and designs as far as hydrology is concerned. And then hydrology design say just like the cross section of the drainage system we can use simple equations like manning's equations or chassis equations for simple design. But whenever we are looking for the flat routing is concerned we have to go for numerical techniques and softwares like HEC, HMS or HEC RAS type of modeling tools. So, for a simple channel design we can use manning's equation like q is equal to a into r to the power 2 by 3 s to the power 1 by 2 divided by n, where n is the manning's reference coefficient, a is the area of cross section, r is the hydraulic radius and s is the slope. For computation of water level profiles in the drainage systems or channel rivers say we can go for suitable softwares for flat routing just like public domain softwares like HEC, HMS for hydrologic modeling of the watershed and then HEC RAS for river modeling or we can go for software like SWMM storm water management model for sewer drainage design. So, that way we can either go for a simple modeling models just like a rational formula or manning's equations or we can go for somewhat complex models like HEC, HMS or HEC RAS which you consider most of the physical parameters as far as the rainfall runoff is considered. So, all future storm water drainage system may be designed to taking into consideration a runoff coefficient up to C is equal to 0.95 for estimating peak discharge using the rational method. If you are using rational method, so maximum possible generally we can consider 0.95 and then say urban drainage system is concerned we also should be we should deal with the operation and maintenance. So, it is not only appropriate design and then implementation, but the operation and maintenance also very important. So, let us look into some of the important aspects as far as the operation and maintenance of the urban drainage system. So, proper operations and maintenance are crucial for any urban drainage system to be functional to the design capacity and for its durability as well. So, you can see that say whenever heavy rainfall or the monsoon takes place say for example, in India during the monsoon period of 4 to 5 months starting from June to September or October. So, we cannot do many of this maintenance during that time. So, we have to do this maintenance work before the monsoon starts. So, that way pre-monsoon desiliting a major operation maintenance activity in most of the cities and watersheds. Then a periodicity of cleaning of drains should be worked out based on the local conditions. So, as I mentioned local conditions like if there is effect of tides or other kinds of parameters which you have to consider, then we have to see whether we have to do before monsoon only or periodically we have to do and then other issues like say removal of solid base. So, you can see that many locations say the drains will be clogged due to the solid base. So, there should be suitable interventions in the drainage system like traps, trash tracks which will reduce the amount of solid base going into the storm sewers. And then also in many of the same storm drainage systems we can see that a sedimentation is a problem, silting is a problem in channels or even pipes. So, we have to see various arrangement like removal of sediments within the say drainage systems. So, sometimes hydrology also we can do this through maintaining certain minimum velocity within the drainage system or say we can also remove it manually. And then also we have to see the inlet connectivity between the major drains and then minor drains and then we have to see how the system to be worked out. And then also as far as urban drainage system is concerned some of the special considerations which we have to see as far as the watershed is concerned like low lying areas should be reserved for parks and other low important impact human activities should be only done. Then wherever unavoidable buildings in low lying areas should be constructed on steels above the high flood level or full tank level. Then for chronic flooding spots alternative locations may be explored for accommodating people staying there. And then a building should be constructed on steels after taking into account the stability of slopes and then storm water drainage system for coastal cities have to be designed taking into account the tidal variations. So, when we look into urban drainage system we have to see all these considerations like a tidal effects then low lying areas and then if any specific areas always flood prone then what kind of measures we can consider like that. So, various special considerations we have to see as far as urban drainage system design is concerned. So, now say what we are discussing is the important aspects as far as urban drainage system its considerations is designed and its requirements so that is what we are discussing. So, now say one of the important urban drainage system generally in urban areas is the roadside drainage system. So, say if we have appropriate roadside drainage system we can see that in most of the urban areas we can reduce the flooding problems to certain extent. So, as I mentioned earlier there was a heavy flooding in on 26 July 2005 in Mumbai due to cloud based effects of rainfall of about more than 940 mm in a time span of 24 hours and then also high tidal effects. So, due to this there were heavy flooding in many locations of Mumbai city and number of people died and then there was huge economic loss. So, that when then we were asked to look into the roadside drainage system as far as the Mumbai city is concerned most of the important roads of Mumbai cities are concerned. So, then we looked into various design aspects of various existing conditions as far as this Mumbai roads are concerned and then we went through all the design procedures as far as roadside drainage design is concerned and then we come up with certain guidelines. So, I will just discuss this roadside drainage design within this context of Mumbai roads which we which we redesigned few years back by considering the various rainfall conditions tidal conditions and then the the road conditions and the side conditions. So, some of the important aspects are listed here. So, as I mentioned roadside drainage integral part of urban drainage systems. So, this is actually storm drainage. So, whatever the the storm water from the nearby areas it will be mainly coming through these roadside drains and then it will be going to the to these larger drainage systems or the Nalas or Stannels. So, the storm drainage here what is happening we collect the storm water runoff then this should be away from structures and through roadway or the waterway or right of way. So, you can see that if this is a the road then we have to collect all this the the storm water coming from adjacent areas and then generally the drainage system storm water drains will be on the sides of the roads and then we have to see appropriate design as far as the roadside drainage system is concerned. So, some of the important objectives for such a design is hydrologic we have to see the hydrologic aspects like in part runoff then we have to see the hydraulic considerations like what kind of section to be given what kind of drain open drain or pipe drain so what kind of drain is to be given. So, the main objective will be minimize the flooding and then erosion to properties and then safe traffic. So, in an urban area if there is the if we can reduce the flood risk through all the roads then most of the inconveniences of course, due to urban flooding can be reduced to a larger extension. So, that way we have to see say when we design the the the roadside drain we have to see the the road layout and then various junctions, various flyovers and various natural drains coming and then wherever say the the cross drainage systems and then the directions then in the slope all these important aspects we have to consider when we look into roadside drainage design. So, as I mentioned say we have formulated the design steps so some of the important design steps we will discuss here. So, design problem and design criteria specification so we should see what kind of design we are looking for then what kind of locality whether just like a crowded place like Mumbai or a small city where not much crowd is there so accordingly we have to see the roadside drainage design. Then the system drainage area definition and preliminary layout so we should get the road layout accordingly we should go for the the drainage and then the drainage area. Then we should get the street layout total drainage then a field and office data collection so we should go to the field and then see the specific problems like the width the say whether in trees are there outcrops, utility locations etcetera then we should come up with the system layout. So, the final layout we should have then like all ditches, waterways, inlets, manholes, mains, laterals, culverts, flow direction etcetera so we have to go systematically. Then next step is hydrologic calculations so we have to identify as far as roadside road is concerned so how much water will be coming from both sides so we have to see that area and then how much is a rainfall possible and then we should go for hydrologic calculations so we may have to go for a hydrologic modeling rainfall runoff. So, flow estimations for the design frequency we have to consider so we have to see the intensity duration frequency curve or return periods which we have to consider 2 years return period or 5 years return period or 50 years return period like that. Then we have to see the street flow like a flow and spread calculations then a maximum spread gutters flow like that. Then inlet spacing and layout so like location and type of inlets, size, extra inlets etcetera then we have to see the hydraulic calculations like size of the drain, permissible velocity, slopes etcetera then various design checks like discharge, fruit number, velocity, slope like this all these parameters we have to consider as far as the roadside drainage design is concerned. So, it is not only hydrologic aspects, but also the hydraulic aspects like size of the drain, velocity, slope etcetera. So, some of the important factors which we have to consider when we go for roadside drainage design is listed here like return period of flow like 2 years return period or 5 years return period or 50 years return period. So, this depends upon the city area and then the importance of the area. Then the water spread area say like when we consider the road both sides how much area whether it is the on a watershed basis or only a strip wise both sides like a 50 meter or 100 meter both sides of the roadside. Then inlet types and spacing so how these flow is coming to the roadside drains so and then what is the spacing for that. Then longitudinal slope we have to see then cross slope then curves and gutter sections so how the curves and how the gutters how this is considered. Then roadside and median channels bridge decks flyover, shoulder gutter, median barriers, storm drains, detention storage, erosion and then what is the cost how much cost say what are the financial layout as far as whether we have to go for very expensive drainage system. So, how we can reduce the cost so all those issues we have to consider. So, these are some of the important factors which we have to consider when we deal with the drainage design. So, some of the important design considerations I have listed here like how much area should be considered for a reach. So, if this is the in the mounts which we consider then both sides how much area we have to consider. So, actual length is in between hydraulic mount to the drainage point so this is the drainage point. So, this is the hydraulic mount so how much area we have to consider. Then second issue is how much width should be considered on other side of the road drainage. Internationally roadside drain are designed to cater only road runoff, but in highly populated area like Mumbai we have to consider the runoff coming from nearby areas also. So, nearby properties or this runoff will be coming to the roadside drains. So, we have to deal that also. So, then actual width should be based on topographical survey and then the roads in Mumbai say for example, we have to see the actual area contributing to roadside since it is heavily populated and then roads are very narrow. So, that way we have to consider. Then third issue which we have to consider is designed rainfall intensity. Generally rainfall intensity with 10 year return period is considered say for important roads it should be about 50 year return period say like a roads connected to airport area like that. Then it should be based on time of concentration and then intensity duration frequency curve. So, Indian road congrats say for example, recommends time of concentration as made of two time periods. One is a time required for the rain water to flow over the road surface and enter into the drain and then time of flow in the drains. So, this is the most stated. So, this is say this is central line of the road this is the road. So, this is T 1 the time of this flow to enter to the roadside drain and then T 2 is say this say how to how much time to reach the main drain or NALA or the channel. So, that way we have to consider the time of concentration is equal to T 1 plus T 2. So, some of the important design considerations say for example, if you consider Indian road congrats in a manual number 50 say for example, Mumbai they suggest say minimum 50 mm per hour rainfall. Then the values are worked out assuming time of concentration of 30 minutes. Then rate of rainfall is 62.5 mm per hour with a return period of 2 years and then average runoff coefficient to be considered 0.6. So, these are the details as given for given in IRC 50 and then like type of surface like bituminous the runoff coefficient can be 0.8 to 0.9, impervious soil 0.44 to 0.65. So, like that depending upon the area and we can consider the runoff coefficients. Then say as far as hydraulic design is concerned if we use the Manning's equations then Manning's coefficient value we have to consider. So, if it is con gate channel then it can vary from 0.0132 to 0.017. For various surface characteristics range of N is given here this we can get from standard literature. Then next important design concerns permissible velocity in the road drains say as far as RCC drains if we consider allowable maximum velocity 6 meter per second and minimum velocity say up to say 0.30 centimeter per second and, but even the 6 meter per maximum is allowed, but restrict it is generally to 3 meter per second as per Indian Road Congress courts. Then another important aspect is width and depth. So, the width is as per the local width available for the construction of the drains. Then depth should be estimated based on Manning's formula as far as possible we can go for rectangular drains. Then economical section is the width is equal to 2 times depth and some places we may have to if we are going for open drains some places we may have to go for further pipe drains. Then as per IRCA50 minimum width of drain should not be less than 250 mm and in case of pipe the minimum diameter should not be less than 450 mm. This is as per Indian Road Congress manual number 50. Then 8th point is slope of the drains like longitudinal slope generally slope should not be less than 0.3 percent, but in flat terrain it can go up to 0.2 percent and slope is designed such a way that the flow is always in subcritical flow. So, there should not be any supercritical flow conditions so that there is any hydraulic jump can take place within the channel that may create further flooding problems. So, as per IRCA50 code minimum longitudinal gradient is 0.3 percent. Then freeboard also we have to when we go for open channel type design 0.3 meter is the in the prescribed freeboard, but say for example in a city like Mumbai flat terrain and does not allow to have more freeboards then IRCA recommends like if the bed width is less than 300 mm freeboard minimum should be 10 centimeter 300 to 900 mm 15 centimeter 900 to 1500 mm 30 centimeter and for larger size it should be 90 centimeter so like that. Then say design concentration like a type of inlet to drains so we can have either curbing lead or we can have greater inlet or we can have combined inlet. So, we should have say depending upon the terrain depending upon the location we should go for the best possible type of inlet to the drains. Then like a junction box size this should be designed as per the velocity of the water crossing the crossing or joining each other. Then as far as the NALA is concerned NALA this all these small drains what will be taking into the NALAs or the streams. So, level difference between the invert level of the maximum water level in the NALA we have to see the invert level of the drain is lower than the maximum water level in NALA then NALA water starts entering to the drains. So, then slope has to be modified and designed in such that the invert level of drains is above the maximum water level of NALA. Then connection between the main drain or either side of the road we have to see. Then points important points like design of drain draining to the creek or NALA having tidal effect. So, as I mentioned in a city like Mumbai tide is an important factor as far as spreading is concerned. So, we have to see that whether the outlet of the drain is to a creek or to a NALA whose water level rises according to the tidal level and the invert level of the drain should be above the high tidal level as seawater may enter to the drain. If possible a large size drain may be constructed which you can act as holding a pond until the high tide level. Then same we need a large quantity of data when we go for the road side drainage system design or the urban drainage design. So, some of the important data like your infalling density and runoff coefficient, area contributing to drains, then cross sectional parameters, the reduced level of the hydraulic mounts, then reduced level of the ground level, invert level of the drains. So, like this all this data required as far as the drainage design is concerned. Then key plan of the work the area like the length location of the NALA size invert level of drains at starting point and draining point, slope between the sections, other major drainage work nearby or river nearby. So, all these key plan should be available. Then detailed plan of the road like a length, location of point sources and their discharges, hydraulic mounts, reduced level of ground levels, then arrows showing the flow direction of storm water in the drains, location of draining NALA, location and size of cross drainage work, location of manholes and their sizes and any other data size specific. So, all this data detailed plan of the road and all the data should be available. Then longitudinal section drawing like a finished road level, reduced level of existing ground level, invert level of drains, wet levels, water levels of NALA, location of curbing inlet points, location and size of other point source joining the drain. So, like this. So, all this data should be available. So, when we go for integrated urban drainage system design, so including the roadside drains and then the NALA system or the channel system. So, we should have integrated drainage design plan. So, that the flood effect if any possibilities that can be reduced and then we can have a better management plans and better design, so that there is no flood problems as far as areas concerned. For today's lecture some of the important references are shown here. Then says before closing the lecture, some tutorial questions and assignment questions. Critically study the urban drainage design methodology adopted in India. Some details you can see in this websites. What are the urban drainage design practices in US, UK and India and propose better management practices for Indian cities? Then few self evaluation questions. What are the important causes of urban flooding? What are the difficulties in urban flood management? Discuss watershed based urban flood management. Describe the inventories to be taken for storm water drainage system. What are the important design consideration for urban drainage systems? What are the important data to be considered for roadside drainage design? So, all these questions you can easily answer by going through today's lecture. Then few assignment questions. What are the important strategies for urban flood disaster risk management? Illustrate various urban drainage systems. What are the important design requirements for urban drainage systems? Discuss the important design considerations for roadside drainage design. What are the important factors to be considered for roadside drainage design? So, these questions also you can answer by going through today's lecture. So, what we discussed today is urban drainage design and then say an integrated design system by considering all the aspects including the roadside drains, NALA system or the channel system. So, that we can have an effective drainage design. Thank you very much.