Has anyone conducted a comprehensive experiment or literature review assessing the curve numbers for different green infrastructure practices (in other words, not just green roofs)? I want to apply the urban runoff methodology from USDA's TR-55 to the entire city of Philadelphia, PA, but I am not sure how to account for the green infrastructure.
It should be fairly simple to use the USEPA SWM model to work out what the equivalent CN values are for different LIDs from a purely modelling perspective. The trick would then be to monitor the performance of real systems and see how different designs would be presented as LIDs.
For example, we've just completed the Functional Design of an LID that uses no pipes, no pond, to provide water quality and quantity treatment for an 85 ha development (cost is slightly more than conventional, not considering the cost of a pond). We are recommending building a test section to answer the questions we can't answer as part of the Conceptual Design - in about 3 years we should have some data. We know how it models, but we need the test sections to have it calibrated.
Data Identification of rainwater harvesting sites using SCS CN me...
https://www.irbnet.de/daten/iconda/CIB8120.pdf
Dear Charlotte, I agree Douglas and Somnath. If you have any observed data it will be useful to calibrate de NCs and adapt their values for these green infrastructures. I suggest you too, to take into account rainfall considerations (determination of number of storms, minimum rainfall depth to be considered in the analysis, minimum inter-storm time, etc), most of the times, the results could change much more than by modifying the NCs. Do have any specific legislation/guide/manual to follow?
Regards, Alvaro
Dear Charlotte,
In my paper 'Estimation of Direct Runoff and inflow Hydro-graphs in Small Un-gauged Catchments' , I have explained how to select appropriate 'Curve Number' based on Catchment Characteristics. You may rifer into that and follow the procedure to estimate excess rainfall (direct runoff) and also the inflow hydro-graph if necessary. If you have observed runoff hydro-graphs with respect to few events, you can verify the estimated CN with the real data.
Prema
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