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Question-Developing hydrographs from index floods & growth curves

Question-Developing hydrographs from index floods & growth curves

Question-Developing hydrographs from index floods & growth curves

I am undertaking a Hydrology study for a specific basin in my Province.  There is no Rain gauge data available in that area....but what I do have is flow data from other lakes/basins in areas nearby my area of study.

My boss has asked me to determine the associated hydrographs for the area based on the other flows from similar lakes/basins.

So far I have developed the index floods from the flow data of other basins, as well as the growth curves.

How do I proceed from here to turn this into the required hydrographs needed for my study?  It is required that I use the SCS Synthetic Unit hydrograph.


RE: Question-Developing hydrographs from index floods & growth curves

You will need a suitable program to generate runoff hydrographs using the SCS Unit Hydrograph procedure.  I suggest you try the free HydroCAD Sampler at www.hydrocad.net

For the SCS method (now NRCS) you will need to specify the appropriate rainfall distribution and rainfall depth, plus the curve number and time-of-concentration for each subcatchment area.  If some of this data is lacking, you may be able to make some estimates based on your "flow data" from nearby areas.  But these values are critical to the result.

If you need background on the runoff procedure see the "Hydrology" section at www.hydrocad.net/training

RE: Question-Developing hydrographs from index floods & growth curves

You might aLSo try the program SMADA.  It has built in utilities for regression analyses and probability distributions which would be very useful for you particular problem.

Also look at the National Flood Frequency program for an explanation of the procedure.  Although it only applicable to the U.S. the approach would be instructive.

Good luck

RE: Question-Developing hydrographs from index floods & growth curves

I am not sure if you understand what I am asking or if I am not getting your advice.  I am using the index flood method and I have generated 2 curves:
1. Qavg vs. Drainage Area (Q = 0.89DA^0.78)
2. Q/Qavg vs. Frequency (I have 1/2, 1/10, 1/100, 1/1000 and 1/10,000) - it is pretty much a straight line when plotted on log paper

What I am not sure on is how to take these 2 plots and turn them into a hydrograph.

Any more suggestions?


RE: Question-Developing hydrographs from index floods & growth curves

I think you're asking about two very different procedures:  The index flood method (for estimating the peak flow) and the SCS Unit Hydrograph procedure (for generating a complete runoff hydrograph, and estimating the peak).  If you want to use the SCS method (as stated in your first post) then you'll need to provide the SCS parameters I mentioned before.

For more info on the index flood procedure, google turned up a number of documents that might be helpful:

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