Article # 1:
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Summary:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on the alternatives considering the traditional and clustered development along with LID technique and with the LID technique. Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales). These alternatives were compared with the existing conditions i.e. without any land development. They have used different metrics to compare the effects of runoff – peak flow, flow duration, time to peak, and runoff volume. The paper focuses on the possible areas of hydrologic concerns with different land developments and storm management practices.
Article # 2:
E. Downey Brill, JR. John M. Flach, Lewis D. Hopkins, S. Ranjithan, MGA: A Decision Support System for Complex Incompletely Defined Problems, August 1990
Summary:
The paper focuses on how the infiltration types effect could be different depending on the type of land development. The study carried out evaluates combinations of different infiltration practices (i.e spread roof to lawn, rain garden, reduction on street width, green swales etc) and they have even carried out comparative analysis of different soil groups with these mentioned infiltration practices. The research proves that the land development which leaves most of the land unaltered i.e. leaving it in natural condition are the ones which have less effects on the urban runoff. With the strategic combinations of land development and corresponding infiltration practices it would be possible to deal with the hydrologic impacts caused due to the increased runoff.
Article # 3:
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Summary:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas. They have carried out different options of irrigation management plans and studied the water budget of the area. Cost comparison was carried out between these options. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit. Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options.
Article # 4:
Kristin L Gilroy, Richard H McCuen, Spatio-temporal effects of low impact development practices, 2009, Journal of hydrology
Summary:
The paper focuses the importance of the factors like optimal location, quantity of BMP and land use types which needs to be investigated to achieve the optimal effectiveness of the LID’s being used for the storm water management. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume. In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. The authors have carried out the study considering different land use patterns and modeled using 2 different storm events 1 yr and 2 yr. They have studied the effectiveness of each of the BMP used with respect to these scenarios. For the comparison of the results they have considered two metrics i.e. peak flow and runoff volume to measure the effectiveness of the scenarios and BMP used.
Article # 5:
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Summary:
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using these strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Article # 6:
Wolfram Schluter, Chris Jefferies, Modeling the outflow from a porous pavement, October 2001
Summary:
This paper focuses on modeling a 20 month old porous pavement in Edinburgh which was calibrated using 15 storm events. Storm water software package Erwin is used to simulate the outflow from these porous pavements. 16 events were recorded out of which one was recorded using the flow logger where as the rest were recorded with the V notch weir located at the outlet of the monitoring manhole. The porous pavement does not drain total inflow but it retains a certain amount which would be evaporated unless a future precipitation occurs. From the conclusion which they observed after running the simulation model for both single event and long term simulation is that the wetness of the porous pavement prior to the event will increase the outflow of the following event. Therefore studying the simulation for long term would be more advisable as it takes into consideration the wetness of the porous pavement. The study observed that Porosity of the filling material under the porous pavement has a little influence on the volume of the runoff but has an impact on the peak flow rate.
Article # 7:
James. W, James W.R.C, Von Langsdorff H, Computer Aided design of permeable concrete block pavement for reducing stressors and contaminants in an urban environment, October 2003
Summary:
This paper focuses on illustrating the new component which is linked up to EPA SWMM which is used to model the permeable pavements called as PCSWMM. The paper gives illustration of all the different components in the PCSWMM. Permeable pavement depends on design of storage capacity (which can store the storm water) and surface infiltration rate. PCSWMM addresses hydraulic and hydrologic aspects of permeable pavement. Two main concerns addressed by the software is the maximum depth of water that can be stored for the designed storm and the time taken to drain from the base layer of the pavement. This interface calculates the flow of runoff through different layers of the pavements i.e. pavers, base layer, and subgrade. The paper did not cover any examples of using this software. The authors mentioned about the groundwater and infiltration calculations need to be tested or verified.
Friday, August 28, 2009
Monday, August 3, 2009
Discussion # 6 (03 Aug 2009) : Common Paper
Article Reference
Zoong Woo Geem, Harmony search optimization to the pump included water distributed network design, Environmental Planning and management program, Sept 2009
Introduction
The paper focuses the optimization of the water distribution system along with the pumps which have not been included in the literature of hydrosystems optimization. Optimal solution obtained by the mathematical model is in terms of continuous pipe diameters and in the means of converting those to available commercial diameters might alter the quality of the solution. However meta heuristic optimization techniques like GA, tabu search etc have been used in optimizing distribution network , these algorithms resulted more discrete pipe diameters than the continuous diameters. This paper focuses applying harmony search in optimizing the cost of the water distribution system including the pumps.
Objective function: design cost function
Decision variable: pipe diameters or pump size
HS model most used parameters range: HM range 30-100, HMCR – 0.95-0.99, PAR – 0.05-0.2
Steps followed in HS method are:
1. Initialization of the HM by selecting the vectors randomly
2. Improvisation of the HM by random selection (randomly selecting the decision variable from HM), memory consideration (using the HMCR the next step HM would be choosen), Pitch adjustment (adjusting the pitch i.e selecting the neighboring value based on the given probability) and violated harmony consideration (the new HM is checked by hydraulic analysis to check the nodal pressure, if the nodal pressures are greater than the limit then penalty is added to the design cost)
3. New HM is replaced by the previous HM if the new HM is a better solution than the old HM
4. Stopping criteria is specified by maximum iterations, so the steps 2 and 3 are continued till it reached the maximum iterations
Problem formulation
• Objective function: Pipe capital cost + pump capital cost + pumping energy cost
• Penalty function: squared penalty value + constant penalty value, if the pressure at the nodes do not meet the minimum criteria
• This penalty function is added to the cost objective function
Model
• 10 commercial diameters considered
• L = 2500 m
• 9 commercial pump sizes considered
• Water demand specified at each node
• Minimum pressure at each node should be 30 m above GL
• No. of pipes = 11
• No. of nodes = 9
Conclusions and Discussion
This research explains using meta heuristic technique in distribution optimization along with four different search behaviors. The same problem was solved using Simulated annealing and the cost was identical to that of HS. However HS produced much lower average cost and within less number of function evaluations.
Zoong Woo Geem, Harmony search optimization to the pump included water distributed network design, Environmental Planning and management program, Sept 2009
Introduction
The paper focuses the optimization of the water distribution system along with the pumps which have not been included in the literature of hydrosystems optimization. Optimal solution obtained by the mathematical model is in terms of continuous pipe diameters and in the means of converting those to available commercial diameters might alter the quality of the solution. However meta heuristic optimization techniques like GA, tabu search etc have been used in optimizing distribution network , these algorithms resulted more discrete pipe diameters than the continuous diameters. This paper focuses applying harmony search in optimizing the cost of the water distribution system including the pumps.
Objective function: design cost function
Decision variable: pipe diameters or pump size
HS model most used parameters range: HM range 30-100, HMCR – 0.95-0.99, PAR – 0.05-0.2
Steps followed in HS method are:
1. Initialization of the HM by selecting the vectors randomly
2. Improvisation of the HM by random selection (randomly selecting the decision variable from HM), memory consideration (using the HMCR the next step HM would be choosen), Pitch adjustment (adjusting the pitch i.e selecting the neighboring value based on the given probability) and violated harmony consideration (the new HM is checked by hydraulic analysis to check the nodal pressure, if the nodal pressures are greater than the limit then penalty is added to the design cost)
3. New HM is replaced by the previous HM if the new HM is a better solution than the old HM
4. Stopping criteria is specified by maximum iterations, so the steps 2 and 3 are continued till it reached the maximum iterations
Problem formulation
• Objective function: Pipe capital cost + pump capital cost + pumping energy cost
• Penalty function: squared penalty value + constant penalty value, if the pressure at the nodes do not meet the minimum criteria
• This penalty function is added to the cost objective function
Model
• 10 commercial diameters considered
• L = 2500 m
• 9 commercial pump sizes considered
• Water demand specified at each node
• Minimum pressure at each node should be 30 m above GL
• No. of pipes = 11
• No. of nodes = 9
Conclusions and Discussion
This research explains using meta heuristic technique in distribution optimization along with four different search behaviors. The same problem was solved using Simulated annealing and the cost was identical to that of HS. However HS produced much lower average cost and within less number of function evaluations.
Friday, July 31, 2009
Discussion # 5 (22 July 2009) : Common Paper
Article Reference
Zoong Woo Geem, Joong Hoon Kim, G V Loganathan, A New heuristic Optimization Algorithm : Harmony Search
Introduction
The paper tries to focus on the new heuristic algorithm called “Harmony Search” (HS) which is explained using three examples – TSP, academic optimization problem and a least cost pipe network design problem. Authors explain the drawbacks of using the normal optimization methods i.e LP, NLP and DP. In LP there are considerable losses associated as the real world non linear model is being expressed as a linear model; In DP increased variable increase the evaluation of the recursive functions; in NLP if the functions are not differentiable then finding optimum is not possible and attention is required to select the initial values in order to guarantee global optima instead of local optima. To overcome the above mentioned drawbacks, heuristic method of optimization is developed which results in near optimum solution within reasonable computation time and within reasonable use of memory. Since 1970 there have been many heuristic algorithms which have been developed combining rules and randomness mimicking the natural processes. The techniques are:
• Simulated annealing (SA) – It is based on the analogy of physical annealing process. In physical annealing as the materials temperature increases the molecules mobility increases and gradually these molecules form the crystalline structure i.e. the optimal solution.
• Tabu search (TS) – it explores the search space of feasible solutions by sequence of moves. To escape from the local optima and to prevent cycling some moves are classified as tabu.
• Evolutionary algorithms (EA) – it is based on the principle of evolution. Consists of four heuristic algorithms- genetic algorithm, evolutionary strategies, evolutionary programming and genetic programming.
• Genetic Algorithm – based on the natural selection and the mechanism of population genetics. It has three operators – reproduction, crossover and mutation. Main advantage of GA when compared to other optimization techniques or heuristic techniques is that GA evaluates different solutions simultaneously unlike the other methods which evaluate on solution at a time.
• Evolutionary strategies
• Evolutionary programming
• Genetic programming
These simulation based heuristic search techniques have powerful search abilities which overcome the drawbacks of the traditional optimization techniques. The paper proposes a new heuristic search technique which produces better solution in less number of iterations than the other techniques.
New Heuristic technique (Harmony Search)
The steps to be followed in this new technique are:
• Step 1 – Initialize a Harmony memory (HM)
• Step 2 – Improvise a new harmony from HM
• Step 3 – If the new harmony is better than the minimum harmony in HM then include the new harmony in the HM and exclude the minimum harmony from HM
• Step 4 – if the stopping criteria are not met then repeat the Step 2.
To improve the solutions and escaping from the local optima there two methods which are introduced, they are:
• Harmony memory considering rate (HMCR): indicates the probability of the algorithm which selects the variable from the harmony memory onto the next step
• Pitch adjusting rate (PAR): shifting the values to nearby neighboring values in the specified range which is called as PAR. PAR 10% means the new value is selected in the probability of 10% (5% of higher value or lower value with 5%)
Major difference between HS and GA is that HS makes a new vector from the existing vectors (i.e from all harmonies in the Harmony memory) where as GA makes new vector only from the two existing vectors (parent).
Examples
1. Travel Salesman Problem – Harmony memory consists of the existing tour lengths, if the new tour length is shorter than the existing HM tour lengths then the new tour length is replaced in the HM. Different HMCR and PAR parameters are considered and the iterations are performed to avoid the local optima solution. For faster convergence two new operators have been introduced – Neighboring city (i.e salesman visiting the closest neighboring city) and city inverting (i.e inverting the city if the former is shorter than the later city).
2. Simple constrained minimization problem – Initially decision variable x1 and x2 have been selected randomly based on the given range later the range has been narrowed to the values in the HM. This problem was solved using generalized reduced gradient (GRG), EP and GA, HS has evolved much better solutions than the other methods.
3. Design of pipe network for water supply – The problem has 32 nodes, 32 links and 3 loops, no pumping station is considered. Minimum pressure requirement at all the nodes is specified. This problem was solved using Nonlinear programming gradient and GA. HS gave a minimum least cost of the pipe network when compared to the other heuristic methods.
Conclusions and Discussion
HS is advantageous than the other methods
- as it makes a new set of vectors based on all existing vectors instead of just two vectors (parent),
- it does not require initial values of the decision variables
- It outperformed the other heuristic techniques (GA, EP etc)
- Faster convergence
Zoong Woo Geem, Joong Hoon Kim, G V Loganathan, A New heuristic Optimization Algorithm : Harmony Search
Introduction
The paper tries to focus on the new heuristic algorithm called “Harmony Search” (HS) which is explained using three examples – TSP, academic optimization problem and a least cost pipe network design problem. Authors explain the drawbacks of using the normal optimization methods i.e LP, NLP and DP. In LP there are considerable losses associated as the real world non linear model is being expressed as a linear model; In DP increased variable increase the evaluation of the recursive functions; in NLP if the functions are not differentiable then finding optimum is not possible and attention is required to select the initial values in order to guarantee global optima instead of local optima. To overcome the above mentioned drawbacks, heuristic method of optimization is developed which results in near optimum solution within reasonable computation time and within reasonable use of memory. Since 1970 there have been many heuristic algorithms which have been developed combining rules and randomness mimicking the natural processes. The techniques are:
• Simulated annealing (SA) – It is based on the analogy of physical annealing process. In physical annealing as the materials temperature increases the molecules mobility increases and gradually these molecules form the crystalline structure i.e. the optimal solution.
• Tabu search (TS) – it explores the search space of feasible solutions by sequence of moves. To escape from the local optima and to prevent cycling some moves are classified as tabu.
• Evolutionary algorithms (EA) – it is based on the principle of evolution. Consists of four heuristic algorithms- genetic algorithm, evolutionary strategies, evolutionary programming and genetic programming.
• Genetic Algorithm – based on the natural selection and the mechanism of population genetics. It has three operators – reproduction, crossover and mutation. Main advantage of GA when compared to other optimization techniques or heuristic techniques is that GA evaluates different solutions simultaneously unlike the other methods which evaluate on solution at a time.
• Evolutionary strategies
• Evolutionary programming
• Genetic programming
These simulation based heuristic search techniques have powerful search abilities which overcome the drawbacks of the traditional optimization techniques. The paper proposes a new heuristic search technique which produces better solution in less number of iterations than the other techniques.
New Heuristic technique (Harmony Search)
The steps to be followed in this new technique are:
• Step 1 – Initialize a Harmony memory (HM)
• Step 2 – Improvise a new harmony from HM
• Step 3 – If the new harmony is better than the minimum harmony in HM then include the new harmony in the HM and exclude the minimum harmony from HM
• Step 4 – if the stopping criteria are not met then repeat the Step 2.
To improve the solutions and escaping from the local optima there two methods which are introduced, they are:
• Harmony memory considering rate (HMCR): indicates the probability of the algorithm which selects the variable from the harmony memory onto the next step
• Pitch adjusting rate (PAR): shifting the values to nearby neighboring values in the specified range which is called as PAR. PAR 10% means the new value is selected in the probability of 10% (5% of higher value or lower value with 5%)
Major difference between HS and GA is that HS makes a new vector from the existing vectors (i.e from all harmonies in the Harmony memory) where as GA makes new vector only from the two existing vectors (parent).
Examples
1. Travel Salesman Problem – Harmony memory consists of the existing tour lengths, if the new tour length is shorter than the existing HM tour lengths then the new tour length is replaced in the HM. Different HMCR and PAR parameters are considered and the iterations are performed to avoid the local optima solution. For faster convergence two new operators have been introduced – Neighboring city (i.e salesman visiting the closest neighboring city) and city inverting (i.e inverting the city if the former is shorter than the later city).
2. Simple constrained minimization problem – Initially decision variable x1 and x2 have been selected randomly based on the given range later the range has been narrowed to the values in the HM. This problem was solved using generalized reduced gradient (GRG), EP and GA, HS has evolved much better solutions than the other methods.
3. Design of pipe network for water supply – The problem has 32 nodes, 32 links and 3 loops, no pumping station is considered. Minimum pressure requirement at all the nodes is specified. This problem was solved using Nonlinear programming gradient and GA. HS gave a minimum least cost of the pipe network when compared to the other heuristic methods.
Conclusions and Discussion
HS is advantageous than the other methods
- as it makes a new set of vectors based on all existing vectors instead of just two vectors (parent),
- it does not require initial values of the decision variables
- It outperformed the other heuristic techniques (GA, EP etc)
- Faster convergence
Discussion # 5 (22 July 2009)
Article Reference
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Introduction
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. They modeled trying to replace the existing loam soil with clay soil and it was observed that annual runoff discharge to the street was increased by 63%. In this study they have considered the case study of Los Angeles which has the polluted runoff being flown into local watershed and thereby into the coastal recreation areas. LA experience sever summer deficit of water demand where they import almost 85% of the water to meet their demands. Author focuses on how the policy makes are considering the implementation of the decentralized approach in the urban watershed i.e creating a mini reservoir system which retains runoff and reducing the irrigation demand but they lack the quantitative data on the effectiveness of the usage of different BMP’s. Most of the urban hydrologic models focus on the water balance and not on the effects on the BMP’s on the hydrologic processes which are dependent on the land use.
Objective of the study:
Develop, calibrate and validate the physical model at the residential scale for simulating the runoff for both long term events and storm term storm events. The study is carried out to see the effectiveness of BMP and simulating the effects of retrofitting the control site with the BMP’s.
Methodology:
• Site: residential housing unit
• BMP’s considered: cistern, swale, rain gutter, lawn retention basin, driveway interceptor and drywell
• Designed for 50 yr storm event
• Runoff from rooftops flowed into cistern and lawn retention basin
• Runoff from driveway flowed into the interceptor and further into the drywell
The data was collected from Jan 2001 to Jan 2003 and the model was calibrated and modeled based on the measurements of land covers, hydrologic processes and micro climate data. The runoff from treatment Site Street was collected in the measurement system and then through the water outlet drainages where as the runoff from the control site was drained directly into the drive way and thereby into the street. Each land cover was considered as a individual modeling unit. The model was studied for both long term simulation and short term events. For the long term simulation the focus of study was taking into consideration the annual irrigation use and runoff to the street and for short term simulation the focus was on the storm runoff to the street and the storage of the BMP.
• Precipitation data taken as the input of the rainfall data
• Two strategies of irrigation (first using the annual ET and second one was based on the soil and water deficit) were used in the model to determine the timing and the amount of water to be applied.
• Interception losses are also taking into consideration in the model
• Surface flow is calculated using the manning’s equation
• Infiltration is estimated using Green Ampt’s equation
• Percolation
• Evapo-transpiration
• Lateral subsurface flow
• Cistern storage is based on the total amount of water entering the cistern and the cistern restricted area
Numerical simulation focused on the landscape irrigation, storm runoff, ET and percolationof runoff into the deep layers, sensitivity analysis of the landscape retrofit was simulated using the date of 2001 and the 50 yr storm event (1988). The purpose of the sensitivity analysis was to distinguish which BMP was more effective with respect to runoff reduction and conservation of landscape irrigation water use. For the control site there were not BMP retrofitted which was considered as the base condition and the treatment site was varied with 6 different BMP’s. Other type of sensitivity analysis was carried by replacing with the clay soil instead of sandy soil.
Results:
Both treatment site and control site had about 50% impervious cover. Field measurement revealed that both cistern and retention basin were more effective in conserving municipal water supplies and reducing the total storm runoff. Surface runoff was effectively reduced by the drive way interceptors and lawn retention basin.
Discussion:
It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using this strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Conclusions
• Most effective BMP is driveway interceptor
• Cistern provided 9% of the annual irrigation demand
• Annual irrigation demand was reduced by 53% by adjusting the irrigation efficiency and application rates based on the plant water demand
• Simulation studies concluded that infiltration and surface runoff is the function of the soil properties and its effective depth
• Selection of the BMP is based on testing the soil properties
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Introduction
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. They modeled trying to replace the existing loam soil with clay soil and it was observed that annual runoff discharge to the street was increased by 63%. In this study they have considered the case study of Los Angeles which has the polluted runoff being flown into local watershed and thereby into the coastal recreation areas. LA experience sever summer deficit of water demand where they import almost 85% of the water to meet their demands. Author focuses on how the policy makes are considering the implementation of the decentralized approach in the urban watershed i.e creating a mini reservoir system which retains runoff and reducing the irrigation demand but they lack the quantitative data on the effectiveness of the usage of different BMP’s. Most of the urban hydrologic models focus on the water balance and not on the effects on the BMP’s on the hydrologic processes which are dependent on the land use.
Objective of the study:
Develop, calibrate and validate the physical model at the residential scale for simulating the runoff for both long term events and storm term storm events. The study is carried out to see the effectiveness of BMP and simulating the effects of retrofitting the control site with the BMP’s.
Methodology:
• Site: residential housing unit
• BMP’s considered: cistern, swale, rain gutter, lawn retention basin, driveway interceptor and drywell
• Designed for 50 yr storm event
• Runoff from rooftops flowed into cistern and lawn retention basin
• Runoff from driveway flowed into the interceptor and further into the drywell
The data was collected from Jan 2001 to Jan 2003 and the model was calibrated and modeled based on the measurements of land covers, hydrologic processes and micro climate data. The runoff from treatment Site Street was collected in the measurement system and then through the water outlet drainages where as the runoff from the control site was drained directly into the drive way and thereby into the street. Each land cover was considered as a individual modeling unit. The model was studied for both long term simulation and short term events. For the long term simulation the focus of study was taking into consideration the annual irrigation use and runoff to the street and for short term simulation the focus was on the storm runoff to the street and the storage of the BMP.
• Precipitation data taken as the input of the rainfall data
• Two strategies of irrigation (first using the annual ET and second one was based on the soil and water deficit) were used in the model to determine the timing and the amount of water to be applied.
• Interception losses are also taking into consideration in the model
• Surface flow is calculated using the manning’s equation
• Infiltration is estimated using Green Ampt’s equation
• Percolation
• Evapo-transpiration
• Lateral subsurface flow
• Cistern storage is based on the total amount of water entering the cistern and the cistern restricted area
Numerical simulation focused on the landscape irrigation, storm runoff, ET and percolationof runoff into the deep layers, sensitivity analysis of the landscape retrofit was simulated using the date of 2001 and the 50 yr storm event (1988). The purpose of the sensitivity analysis was to distinguish which BMP was more effective with respect to runoff reduction and conservation of landscape irrigation water use. For the control site there were not BMP retrofitted which was considered as the base condition and the treatment site was varied with 6 different BMP’s. Other type of sensitivity analysis was carried by replacing with the clay soil instead of sandy soil.
Results:
Both treatment site and control site had about 50% impervious cover. Field measurement revealed that both cistern and retention basin were more effective in conserving municipal water supplies and reducing the total storm runoff. Surface runoff was effectively reduced by the drive way interceptors and lawn retention basin.
Discussion:
It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using this strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Conclusions
• Most effective BMP is driveway interceptor
• Cistern provided 9% of the annual irrigation demand
• Annual irrigation demand was reduced by 53% by adjusting the irrigation efficiency and application rates based on the plant water demand
• Simulation studies concluded that infiltration and surface runoff is the function of the soil properties and its effective depth
• Selection of the BMP is based on testing the soil properties
Friday, July 10, 2009
Discussion # 4 (10 July 2009)
Article Reference:
Kristin L Gilroy, Richard H McCuen, Spatio-temporatl effects of low impact development practices, 2009, Journal of hydrology
Introduction:
Many hydrologists are taking up the option of Best Management practices which is majorly coz of their cost effectiveness. As it is known that with the increase of urbanization, impervious surface increases which prevents water from infiltrating. This prevention of infiltration reduces the ground water recharge, lowers the water table, increasing the surface runoff and reducing the base flow during the dry periods. These add to degrading the stream channels and increasing the transport of pollutants. With storm management plans like detention pond, wet pond and infiltration basin which though they reduce the downstream peak discharge, issue of increased runoff into the stream continue which harms the aquatic life in the stream. Author points out as to the dependency of finding out the factors like optimal location, quantity of BMP and land use types needs to be investigated to achieve the optimal effectiveness of the LID’s. According to study carried out by Schneider et.al (2006) cisterns have showed to be more effective for the small storms when compared to large storms. Various studies concluded that infiltration technique is beneficial depending on the soil texture and the rainfall event size. According to Brander et. Al (2004) using numerous infiltration technique is more effective than few conventional practices with equivalent volume. Hood et. Al (2007) carried out the comparative study with LID development and traditional development which showed that the peak discharge, runoff volume and lag time is reduced and especially for smaller storms and shorter durations. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume.
Methodology:
Spatial Temporal micro watershed model was developed in Matlab taking into consideration both spatial and temporal characteristics of rainfall and runoff processes of any return period on the lot sized watershed. The study was carried out for 1 yr (2.2 cm) and 2 yr (3.6 cm) events and for 4 watershed layouts (i.e. forested and three varying development patterns – townhome with 35% impervious land, residential with 32.5% impervious cover, and commercial land use with 72% impervious cover). In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. From the long term precipitation records in Middle Atlantic region 50% of the storm events are 2 yr or less and of 1 hr duration.
Each lot was assumed to be of 0.1 ha. The model created grids of 20 x 12 cells. For the residential and townhome development, runoff from the roadways is directed onto the grass. Surface runoff of each cell is calculated differently which contained bio retention facility and with cisterns. Cisterns are used only to intercept the rooftop runoff. Outflow from the cistern is drained through the orifice. Once the storage of the cistern is reached, the outflow occurs through the cistern. In the bio retention cells once the depth of the stored water exceeds the storage it overflow where the overflow is equal to total volume of water in storage minus the maximum storage capacity of the facility and this is directed to the down gradient cell.
Results:
Onsite effects on the development
The comparison was made between the type of land pattern (forest, residential, townhome, and commercial) with respect to the two hydrologic metrics i.e. peak discharge and the total volume. It was observed that 1 yr storm was totally infiltrated in the forest pattern i.e. pre development condition. The development patterns have reduced the infiltration potential by increasing the impervious cover.
Effectiveness of cisterns
Effectiveness of cisterns was studied by analyzing the different land patterns with 1 and 2 yr storm events. It was observed that cisterns were more effective with smaller storm, there was about 30% reduction of peak discharge for single family lot for 1 yr storm where as it was only 10% reduction for 2 yr rainfall. If cistern is the only type of BMP in the site then they are ineffective for 2 yr storm, where as they provide some control for smaller events. Volume of cistern should be based on the volume of the runoff at the time of maximum rainfall intensity.
Effectiveness of bio retention location
For the study they have considered the location of bio retention near the cistern overflow, around the outlet of the micro watershed, along the roadway in residential/townhome lot and along the parking lot in commercial lot. There was effective reduction in the runoff volume when bio retention intercepted the roadway runoff and cisterns intercepted the rooftop runoff. But considering the bio retention at the overflow of the cisterns was more effective in reducing the peak discharge, as cisterns storage is reached before the highest storm intensity with bio retention facility there would be storage to control the peak. Location and volume of BMP is dependent on the time of distribution of the rainfall event. Location of bioretention did not make much of a reduction in the total runoff volume as the impervious land cover was greater when compared to the bio retention storage. Whereas peak discharge was decreased with the cisterns storing the runoff and overflow from the cisterns was drained to bio retention facilities.
Effect of storage volume
It was observed that effect of storage volume depends majorly on the land use type. For 1 yr storm event for commercial lot, it was noticed that when the facilities were doubled the peak discharge was reduced by 10% and volume to 30%. Author makes an observation that number of additional facilities is dependent on each watershed which might improve the hydrology.
Varying effects on hydrologic metrics
The two metrics considered to measure the effectiveness of the LID are peak discharge and total runoff volume. Effect of changing the volume of the storage on these two metrics vary as runoff volume can be controlled with the increased storage
Discussion:
I personally found this article interesting as they have tried to check the effectiveness of the LID’s considered, which would be similar to what I am trying to do in my thesis. Check the effectiveness of the RHS and PP in improving the hydrologic condition of the study area. This paper would be helpful when I take up the option of optimizing the location of the LID’s I am considering. For my thesis I would like to measure the two metrics they have mentioned and use Marcio’s HFR metric to analyze the impacts.
Kristin L Gilroy, Richard H McCuen, Spatio-temporatl effects of low impact development practices, 2009, Journal of hydrology
Introduction:
Many hydrologists are taking up the option of Best Management practices which is majorly coz of their cost effectiveness. As it is known that with the increase of urbanization, impervious surface increases which prevents water from infiltrating. This prevention of infiltration reduces the ground water recharge, lowers the water table, increasing the surface runoff and reducing the base flow during the dry periods. These add to degrading the stream channels and increasing the transport of pollutants. With storm management plans like detention pond, wet pond and infiltration basin which though they reduce the downstream peak discharge, issue of increased runoff into the stream continue which harms the aquatic life in the stream. Author points out as to the dependency of finding out the factors like optimal location, quantity of BMP and land use types needs to be investigated to achieve the optimal effectiveness of the LID’s. According to study carried out by Schneider et.al (2006) cisterns have showed to be more effective for the small storms when compared to large storms. Various studies concluded that infiltration technique is beneficial depending on the soil texture and the rainfall event size. According to Brander et. Al (2004) using numerous infiltration technique is more effective than few conventional practices with equivalent volume. Hood et. Al (2007) carried out the comparative study with LID development and traditional development which showed that the peak discharge, runoff volume and lag time is reduced and especially for smaller storms and shorter durations. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume.
Methodology:
Spatial Temporal micro watershed model was developed in Matlab taking into consideration both spatial and temporal characteristics of rainfall and runoff processes of any return period on the lot sized watershed. The study was carried out for 1 yr (2.2 cm) and 2 yr (3.6 cm) events and for 4 watershed layouts (i.e. forested and three varying development patterns – townhome with 35% impervious land, residential with 32.5% impervious cover, and commercial land use with 72% impervious cover). In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. From the long term precipitation records in Middle Atlantic region 50% of the storm events are 2 yr or less and of 1 hr duration.
Each lot was assumed to be of 0.1 ha. The model created grids of 20 x 12 cells. For the residential and townhome development, runoff from the roadways is directed onto the grass. Surface runoff of each cell is calculated differently which contained bio retention facility and with cisterns. Cisterns are used only to intercept the rooftop runoff. Outflow from the cistern is drained through the orifice. Once the storage of the cistern is reached, the outflow occurs through the cistern. In the bio retention cells once the depth of the stored water exceeds the storage it overflow where the overflow is equal to total volume of water in storage minus the maximum storage capacity of the facility and this is directed to the down gradient cell.
Results:
Onsite effects on the development
The comparison was made between the type of land pattern (forest, residential, townhome, and commercial) with respect to the two hydrologic metrics i.e. peak discharge and the total volume. It was observed that 1 yr storm was totally infiltrated in the forest pattern i.e. pre development condition. The development patterns have reduced the infiltration potential by increasing the impervious cover.
Effectiveness of cisterns
Effectiveness of cisterns was studied by analyzing the different land patterns with 1 and 2 yr storm events. It was observed that cisterns were more effective with smaller storm, there was about 30% reduction of peak discharge for single family lot for 1 yr storm where as it was only 10% reduction for 2 yr rainfall. If cistern is the only type of BMP in the site then they are ineffective for 2 yr storm, where as they provide some control for smaller events. Volume of cistern should be based on the volume of the runoff at the time of maximum rainfall intensity.
Effectiveness of bio retention location
For the study they have considered the location of bio retention near the cistern overflow, around the outlet of the micro watershed, along the roadway in residential/townhome lot and along the parking lot in commercial lot. There was effective reduction in the runoff volume when bio retention intercepted the roadway runoff and cisterns intercepted the rooftop runoff. But considering the bio retention at the overflow of the cisterns was more effective in reducing the peak discharge, as cisterns storage is reached before the highest storm intensity with bio retention facility there would be storage to control the peak. Location and volume of BMP is dependent on the time of distribution of the rainfall event. Location of bioretention did not make much of a reduction in the total runoff volume as the impervious land cover was greater when compared to the bio retention storage. Whereas peak discharge was decreased with the cisterns storing the runoff and overflow from the cisterns was drained to bio retention facilities.
Effect of storage volume
It was observed that effect of storage volume depends majorly on the land use type. For 1 yr storm event for commercial lot, it was noticed that when the facilities were doubled the peak discharge was reduced by 10% and volume to 30%. Author makes an observation that number of additional facilities is dependent on each watershed which might improve the hydrology.
Varying effects on hydrologic metrics
The two metrics considered to measure the effectiveness of the LID are peak discharge and total runoff volume. Effect of changing the volume of the storage on these two metrics vary as runoff volume can be controlled with the increased storage
Discussion:
I personally found this article interesting as they have tried to check the effectiveness of the LID’s considered, which would be similar to what I am trying to do in my thesis. Check the effectiveness of the RHS and PP in improving the hydrologic condition of the study area. This paper would be helpful when I take up the option of optimizing the location of the LID’s I am considering. For my thesis I would like to measure the two metrics they have mentioned and use Marcio’s HFR metric to analyze the impacts.
Monday, June 29, 2009
Discussion # 3 (26 June 2009)
Article Reference:
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Introduction:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas.
Methodology:
Study area: Sub-division of Boulder, CO
Area: 11 acres
Drainage: generally running downward to the swale to the south
Approach used in hydrologic analysis: simple water budget principles (setting a control volume around the soil column)
Method to determine Infiltration: Green Ampt Method (Parameters dependent are hydraulic conductivity, soil suction head and difference between the moisture content and porosity)
Network: Building runoff (impervious) is directed to the pervious areas and eventually drained into the conveyance channel.
First approach:
• They used the weather data to predict the PET (hourly)
• Infiltration, Runoff is calculated using Green Ampt method (5 min)
• Soil Moisture conditions assumed to be same over the hour
• Irrigation/rainfall (hourly)
• Total Water balance is estimated using (Infiltration, runoff, rainfall, soil moisture, and irrigation)
• Runoff from each impervious block is determined by routing through the drainage channel
Comparative approach:
• SCS method to estimate the rainfall-runoff response
• Model depends on CN and time of concentration
• Varying the CN with hydrologic conditions will adapt the model to different soil moisture conditions
Cost Estimating Procedure:
In order to evaluate different water management options we need to see the cost effectiveness of different approaches on micro level. From customers point of view the cost can be split into three categories- Water use, on site water management and water pollution control. Investments made on on-site water management typically reduce the water use costs. Water pollution control cost is mostly not borne by the customer unless there is substantial outdoor water demand.
Results:
They have carried out different options of irrigation management plans and studied the water budget of the area. Few of the options studied are mentioned below:
• No irrigation
• Irrigation 1in/week
• Irrigation 2in/week
• Irrigation = 70% of 24 h ET
• Irrigation = 1 in/week with soil moisture sensor which cuts off the irrigation once the soil is saturated
• Irrigation = 1 in/week with Rain water storage (50000L) which is 50% full therefore 50% is catered to peak flow control
Cost comparison was carried out between these options with respect to the three categories of the outdoor costs. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit.
Discussion:
Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options. I was not very sure about how they have calculated the cost components for the irrigation options they have considered. On a whole this paper was very informative about how the design and analysis of the combining water supply and storm water management is done. This paper will be very useful for my literature review and would be helpful if I further extend my research taking into consideration the irrigation plans for the rain water harvesting.
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Introduction:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas.
Methodology:
Study area: Sub-division of Boulder, CO
Area: 11 acres
Drainage: generally running downward to the swale to the south
Approach used in hydrologic analysis: simple water budget principles (setting a control volume around the soil column)
Method to determine Infiltration: Green Ampt Method (Parameters dependent are hydraulic conductivity, soil suction head and difference between the moisture content and porosity)
Network: Building runoff (impervious) is directed to the pervious areas and eventually drained into the conveyance channel.
First approach:
• They used the weather data to predict the PET (hourly)
• Infiltration, Runoff is calculated using Green Ampt method (5 min)
• Soil Moisture conditions assumed to be same over the hour
• Irrigation/rainfall (hourly)
• Total Water balance is estimated using (Infiltration, runoff, rainfall, soil moisture, and irrigation)
• Runoff from each impervious block is determined by routing through the drainage channel
Comparative approach:
• SCS method to estimate the rainfall-runoff response
• Model depends on CN and time of concentration
• Varying the CN with hydrologic conditions will adapt the model to different soil moisture conditions
Cost Estimating Procedure:
In order to evaluate different water management options we need to see the cost effectiveness of different approaches on micro level. From customers point of view the cost can be split into three categories- Water use, on site water management and water pollution control. Investments made on on-site water management typically reduce the water use costs. Water pollution control cost is mostly not borne by the customer unless there is substantial outdoor water demand.
Results:
They have carried out different options of irrigation management plans and studied the water budget of the area. Few of the options studied are mentioned below:
• No irrigation
• Irrigation 1in/week
• Irrigation 2in/week
• Irrigation = 70% of 24 h ET
• Irrigation = 1 in/week with soil moisture sensor which cuts off the irrigation once the soil is saturated
• Irrigation = 1 in/week with Rain water storage (50000L) which is 50% full therefore 50% is catered to peak flow control
Cost comparison was carried out between these options with respect to the three categories of the outdoor costs. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit.
Discussion:
Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options. I was not very sure about how they have calculated the cost components for the irrigation options they have considered. On a whole this paper was very informative about how the design and analysis of the combining water supply and storm water management is done. This paper will be very useful for my literature review and would be helpful if I further extend my research taking into consideration the irrigation plans for the rain water harvesting.
Friday, June 12, 2009
Discussion # 1 (12 June 2009)
Article Reference:
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Introduction:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on four alternatives-
1. Traditional land development (full lot size as specified by county rules) with conventional (i.e. pond) storm management system
2. Cluster development i.e. reducing the lot size to half with conventional (i.e. pond) storm management system
3. Traditional land development with LID technique i.e. emphasizing on vertical storage
4. Cluster land development with LID technique i.e. emphasizing on vertical storage
Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales).
Above mentioned different alternatives were compared with the existing conditions i.e. without the land development.
Results:
Peak flow: Scenarios studied- Existing, without depression storage and with depressions storage. It was observed that two year peak timing change was minimal when compared to 25 yr storm event. LID designs could not meet the peak flow control without the depression storage.
Runoff Volume: Reduction in the runoff volume was observed when the footprint was reduced and using the directly connecting systems. Further reduction of volume was noticed with the usage of infiltration.
The results show that when they ran a continuous model (4 months data) which showed that LID did not perform as expected especially during tropical storms as the soil moisture content is greater than the average condition.
Conclusion:
Infiltration based storm management might perform worse when the soil moisture are above the average value thereby reducing the infiltration or percolation rate. Author mentions about using LID to control the peak upto a certain event beyond which depression storage need to used to control the larger events with this both the quality and quantity concerns are met. This study basically illustrates the impact of using connect and disconnected impervious cover, different types of developments (traditional and clustered type) and usage of conventional pond in addition to infiltration media.
Discussion:
There have been many limitations associated with the study such as using lumped modeling approach, but then this study gives a idea of how the different land developments and different storm management techniques could affect the hydrology of the watershed. This study illustrates how conventional pond system would be required even along with LID (infiltration based) to meet the peak flow control requirement for larger storms.
This paper though doesnot speak about different types of LID’s which could be used, it explains about how the hydrology is differed with different planning methods. In the similar grounds I would like to compare the behavior of the catchment hydrology based on the LID strategies I am going to consider. Through this paper I got the idea of what are all the components of comparison I can make between the scenarios or alternatives I run.
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Introduction:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on four alternatives-
1. Traditional land development (full lot size as specified by county rules) with conventional (i.e. pond) storm management system
2. Cluster development i.e. reducing the lot size to half with conventional (i.e. pond) storm management system
3. Traditional land development with LID technique i.e. emphasizing on vertical storage
4. Cluster land development with LID technique i.e. emphasizing on vertical storage
Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales).
Above mentioned different alternatives were compared with the existing conditions i.e. without the land development.
Results:
Peak flow: Scenarios studied- Existing, without depression storage and with depressions storage. It was observed that two year peak timing change was minimal when compared to 25 yr storm event. LID designs could not meet the peak flow control without the depression storage.
Runoff Volume: Reduction in the runoff volume was observed when the footprint was reduced and using the directly connecting systems. Further reduction of volume was noticed with the usage of infiltration.
The results show that when they ran a continuous model (4 months data) which showed that LID did not perform as expected especially during tropical storms as the soil moisture content is greater than the average condition.
Conclusion:
Infiltration based storm management might perform worse when the soil moisture are above the average value thereby reducing the infiltration or percolation rate. Author mentions about using LID to control the peak upto a certain event beyond which depression storage need to used to control the larger events with this both the quality and quantity concerns are met. This study basically illustrates the impact of using connect and disconnected impervious cover, different types of developments (traditional and clustered type) and usage of conventional pond in addition to infiltration media.
Discussion:
There have been many limitations associated with the study such as using lumped modeling approach, but then this study gives a idea of how the different land developments and different storm management techniques could affect the hydrology of the watershed. This study illustrates how conventional pond system would be required even along with LID (infiltration based) to meet the peak flow control requirement for larger storms.
This paper though doesnot speak about different types of LID’s which could be used, it explains about how the hydrology is differed with different planning methods. In the similar grounds I would like to compare the behavior of the catchment hydrology based on the LID strategies I am going to consider. Through this paper I got the idea of what are all the components of comparison I can make between the scenarios or alternatives I run.
Subscribe to:
Posts (Atom)
