Hi
I am sending a pdf file which has a Soil/Land use Curve Number that are a little bit different with the library into the software.
1-Please let me know how can I add a new library based on those
2-In the attached file there is a graph for Antecedent Mosisture condition.
3-where can I find the time to peak calculated in the software?
I will send a design example based on that, could you please show me how can I model that example into the SewerGems?
Thanks
Hamid
I put some part of the guideline from Ministry of Transportation-Canada:
SCS CN Procedure:
The SCS method uses a parameter called the curve number (CN). CN is a measure of a watershed's hydrologic response potential.
The CN is related to the land use and the hydrologic soil groups, A,B,C, and D, with A being for low runoff potential soils, and D being for high runoff potential soils. The higher the CN, the higher the runoff potential. CN is given in tables in "Modern Sewer Design" or the "National Engineering Handbook". In this procedure, there are also three levels of antecedent moisture conditions (AMC). AMC I is when the soils are dry. AMC II is the average case. AMC III is used to model saturated soil conditions. AMC III conditions are assumed when modeling the final 12 hours of the Hurricane Hazel event. AMCII conditions are assumed when modeling for the Timmins Storm event. The CN is modified according to the antecedent moisture conditions.
S is related to the curve number CN by:
S=25400/CN- 254
In the CN procedure, the initial abstraction Ia is calculated by 0.2 S.
For small rainfall events, the runoff volumes may be underestimated as the Ia value can be high for some CN values. Therefore in OTTHYMO the Ia value can be directly specified (i.e. 1.5 mm) as a more realistic estimate. The corresponding modified CN that result in the same runoff volume are called CN*. Charts can be plotted to compare CN and CN*. For different values of Ia, there would be different charts. Where available, use the calibrated CN’s used in watershed plans, sub-watershed plans or master drainage studies. Sources for all modeling approaches must be provided for the selection / calculation of Curve Numbers, Runoff Coefficients, Initial Abstraction, Time of Concentration, Overland Flow Lengths, Manning Roughness Coefficients, Infiltration Rates, Orifice and Weir Coefficients.
Not to mention, in Canada companies are using VisualOTTHYMO for the hydrological modelling and recently InfoWORKS ICM is coming to the market.
I have planing to present SewerGEMS to my co-workers to convince them it can do whatever they want, I will wonder if you say: I can't enter Ia manually!Because they want to model all the stuff automatically.
Thanks in advance and looking forward to hearing from you.
Regards
Answer Verified By: Sushma Choure