Assignment #7 - Infiltration Based BMP Optimization

Review Article

1) Article Reference
Perez-Pedini C, Limbrunner JF, Vogel RM (2005) “Optimal location of infiltration-based best management practices for storm water management,” JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT, 131(6) pp. 441-448

2) Summary
This paper presents an approach to optimize the location of infiltration based best management practices to reduce peak flow during storm events. According to the author many optimization applications were previously developed to find optimal location, design and operation of detention ponds in a watershed to reduce peak flow.
The infiltration based best management practices considered are infiltration basins, rain gardens and pervious pavements. The approach to integrate a wide variety of distributed storage and infiltration storm water controls acting in combination have been called as low impact development (LID).
According to the author the major goal of this study is to introduce a methodology to determine the optimal number and location of infiltration based practices to reduce peak flow. It was used a fully distributed model based on the SCS curve number approach. The model was applied to the Aberjona River watershed. This model was programmed in excel and VBA with a system of 4533 square HRUs that have a side length of 120 m. It was used the D8 algorithm for runoff routing. A detailed description of all mathematical formulas used to model the water movement within the distributed model was presented. This model was then calibrated for a storm event using 15 min storm data from two rain gages and compared with a flow gage at the watershed outlet.
The optimization routines were developed using excel and a commercial available Genetic Algorithm optimizer called Evolver. The overall goal of the optimization was to locate the HRUs which if BMPs were applied, would lead to a maximum reduction of peak flow. Some restrictions were applied in order to reduce the feasible space. The author also provided some details of the constraints used in the Genetic Algorithm programming.
As the main results the authors showed a Trade off curve between the reduction of peak flow and the number of best management practices to be implemented. The optimum locations were also presented in maps showing its location within the watershed. The authors concluded that a GA algorithm with a distributed hydrologic model presented satisfactory results for finding the optimal locations and quantity of BMPs to reduce peak flow.

3) Discussion
These papers are getting better and better to read. This one was especially nice as it is easy to understand and I am more familiar with the concepts used throughout the research. I think the authors had a good idea developing this application as it seems a new approach using consolidated methods. This is quite encouraging as I am feeling that the amount of my understanding of the article is increasing significantly.

Assignment #6

Review Article
1) Article Reference
Behera, P, Papa, F., Adams, B (1999) “Optimization of Regional Storm-Water Management Systems” Journal of Water Resources Planning and Management, 125(2) pp. 107-114

2) Summary
The paper discusses the application of optimization methods for storm water management systems. As new lands are being occupied, land developers and municipalities have to deal with runoff quantity and quality control. One of the most common solutions adopted are the implementation of detention ponds followed by a number of Best Management Practices available nowadays. In this case, the detention ponds referred as storm water management (SWM) ponds are considered to control both quantity and quality for a given catchment.
To support finding the best alternative for this projects, optimization using dynamic programming is used to find the best design parameters such as storage volume, release rate and pond depth. The objective is to minimize the costs of implementing the SWM ponds in each of the catchments. The authors consider costs related to the value of land, construction, and operation, maintenance and repair. The decision variables are the active storage volume of the pond, controlled release rate of the pond, and pond depth.
The system constraints are based on two major categories: Runoff Control Performance and Pollution Control Performance. The runoff model inputs statistical meteorological data and transform to runoff considering catchment hydrology and control systems hydraulics. The pollution control is modeled considering the average annual fraction of suspended solids removed from the SWM pond.
The constrains and the conceptual models for the optimization of SWM pond design for single catchment are explained as well as the previous work done in the area and the assumptions made. For the multiple parallel catchments the authors also present an specific model, with a optimization function and constrains for pollution control and runoff. Some details about the computations are also provided.
The authors concludes that is possible to optimize SWM ponds using dynamic programming and to achieve optimal design criteria’s considering single catchment and multi-catchment systems with water quantity and quality aspects. They also suggest different uses such as planning activities, preliminary design and scenario analyses.

3) Discussion
I personally enjoyed more this paper than the other previous two. Maybe because I am more familiar with the conceptual models of storm water systems and I actually find this area more interesting. One thing that really surprised me was to realize that the first author of the paper is a graduate student of the civil engineering department like us. As this is the first of this kind we are dealing I still haven’t completely understood the paper. I´m hoping to clarify it better on the class discussion on Wednesday. See you guys there…