Summer Summary

This post is a summary of the main ideas collected during the research period of summer. In total, I read completely 16 articles, and another number of incompletely readings. The research focused mainly in two topics: my present research, which is stormwater sustainability, and optimization techniques, mainly focused in multi-objective genetic algorithm.

For the first and more important topic of my research in this summer, the readings helped me to support the main ideas of the hydrologic footprint residence. HFR is a new metric used to assess the impacts of urbanization in the hydrologic flow regime. Many articles served as references to characterize the impact of urbanization in the hydrological regime. The transformation of natural land covers as forest and grassland to impervious covers alters most of the hydrological processes such as interception, evapotranspiration, infiltration and overland runoff.

In the revised literature, it was identified the main hydrologic metrics used to assess the impact of urbanization. Most of the metrics are based in time series of flow discharges. The main metrics found are: flow frequency curve, flow duration curve, TQmean, which is fraction of year that flow rate exceeds the mean flow rate of the entire flow time series, TQ0.5yr, which is the fraction of year that the flow rate exceeds the historical half-year peak flow rate, peak flow, storm flow duration, time-to-peak, ratio of time-to-peak to storm flow event duration, event-mean rise rate, event-mean fall rate, duration that the flow rate exceeds 75% of the peak flow rate in an event, ratio of event-peak-duration to total event duration, and IHA (indices of hydrological alteration). Those metrics can be used to evaluate different alternatives of development, Best Management Practices (BMPs) and Low Impact Development (LID).

Besides that, an interesting discussion about the effectiveness of BMPs was addressed in some articles. The argument is BMPs introduces a sustained flow for most of the storms which can harm downstream communities. BMPs are design to attenuate bigger storms. Besides that, urbanization increases the frequency of flow events. The combination of more frequent events with sustained flow is being questioned by recent researches.

Another topics explored during this research are the links between the hydrological flow regime and heath of instream ecosystems. Poff et al (1997) summarizes the knowledge about formation of habitats and the natural hydrological regime. Scientific community agrees that stream is a master variable for instream environments because it regulates most of biological and physicochemical processes in rivers. The natural variability of low and high flows plays a crucial role in the entire life cycle of instream and riverine species. Watershed management has been limited to water quality and one aspect of water quantity, which is minimum flow.

The second set of articles is related to optimization algorithms. Two interesting articles present a new heuristic optimization technique called Harmony Search (HS). HS is inspired the way musician improvise harmony searching for maximize the aesthetic estimation of music (objective function). The decision variables are the pitches (sounds) musicians play. Several problems are tested in the articles, and HS presented better performance when compared to other optimization techniques such as Generalized Reduced Gradient (GRC), Evolutionary Programming (EP), Genetic Algorithm (GA), and Nonlinear Programming Gradient (NLPG). This better efficiency, however, should be looked with attention, since performance of methods can be highly dependent of parameters and the problems itself.

The last group of articles is focused in Multi-objective optimization techniques, more specifically genetic algorithms. The objective here is to understand the main operators used in different techniques. Two methods have been studied in more details: MOGA and NSGA-II. One article combined the use of MOGA and Constrained Differential Dynamic Programming in a surface reservoir allocation problem.

In summary, important goals have been achieved during this summer period. The idea of reading two papers a week, one specific of my research and other more general, to discuss in the research group is really efficient. My reading and writing skills have improved a lot in period. I hope we can continue to do that with, hopefully, more students contributing to the discussion.

End of Summer I - List of articles

The summer is over... here is the list of articles that I read in this period:

1. Bertrand-Krajewski, J.-L., Barraud, S., and Chocat, B. (2000). "Need for improved methodologies and measurements for sustainable management of urban water systems." Environmental Impact Assessment Review, 20(3), 323-331.
2. Deb, K., Pratap, A., Agarwal, S., and Meyarivan, T. (2002). "A fast and elitist multiobjective genetic algorithm: NSGA-II." Evolutionary Computation, IEEE Transactions on, 6(2), 182-197.
3. Derek B. Booth, James R. Karr, Sally Schauman, Christopher P. Konrad, Sarah A. Morley, Marit G. Larson, and Stephen J. Burges. (2004). "Reviving Urban Streams: Land Use, Hydrology, Biology, and Human Behavior." Journal of the American Water Resources Association, 40(5), 1351-1364.
4. Egderly, J. L., Roesner, L. A., Rohrer, C. A., and Gironas, J. A. "Quantifying Urban-Induced Flow Regime Alteration and Evaluating Mitigation Alternatives Using Mathematical Models and Hydrologic Metrics." 425.
5. Fan, C., and Li, J. (2004). "A Modelling Analysis of Urban Stormwater Flow Regimes and their Implication for Stream Erosion." Water Quality Research Journal of Canada, 39(4), 356-61.
6. Geem, Z. W. (2009). "Harmony search optimisation to the pump-included water distribution network design." Civil Engineering and Environmental Systems, 26(3), 211 - 221.
7. Getter, K. L., Rowe, D. B., and Andresen, J. A. (2007). "Quantifying the effect of slope on extensive green roof stormwater retention." Ecological Engineering, 31(4), 225-231.
8. Graham, P., Maclean, L., and Medina, D. (2004). "The Role of Water Balance Modelling in the Transition to Low Impact Development." Water Quality Research Journal of Canada, 39(4), 331-42.
9. Konak, A., Coit, D. W., and Smith, A. E. (2006). "Multi-objective optimization using genetic algorithms: A tutorial." Reliability Engineering & System Safety, 91(9), 992-1007.
10. McCuen, R. H. (1979). "Downstream Effects of Stormwater Management Basins." Journal of the Hydraulics Division, 105(11), 1343-1356.
11. Nehrke, S. M., and Roesner, L. A. (2004). "Effects of Design Practice for Flood Control and Best Management Practices on the Flow-Frequency Curve." Journal of Water Resources Planning and Management, 130(2), 131-139.
12. Poff, N. L., Allan, J. D., Bain, M. B., Karr, J. R., Prestegaard, K. L., Richter, B. D., Sparks, R. E., and Stromberg, J. C. (1997). "The Natural Flow Regime." BioScience, 47(11), 769-784.
13. Reddy, M., and Kumar, D. (2006). "Optimal Reservoir Operation Using Multi-Objective Evolutionary Algorithm." Water Resources Management, 20(6), 861-878.
14. Roesner, L. A., Bledsoe, B. P., and Brashear, R. W. (2001). "Are Best-Management-Practice Criteria Really Environmentally Friendly?" Journal of Water Resources Planning and Management, 127(3), 150-154.
15. Yang, C.-C., Chang, L.-C., Yeh, C.-H., and Chen, C.-S. (2007). "Multiobjective Planning of Surface Water Resources by Multiobjective Genetic Algorithm with Constrained Differential Dynamic Programming." Journal of Water Resources Planning and Management, 133(6), 499-508.
16. Zong Woo Geem, Joong Hoon Kim, and Loganathan, G. V. (2001). "A New Heuristic Optimization Algorithm: Harmony Search." SIMULATION, 76(2), 60-68.