HEC-1 in semi-arid regions

[mlridg]

Any suggestions regarding watershed models that include SINKS, typical of Nevada Basin and Range hydrologic area? I'm trying to determine the best parameters to use in HEC-1/HEC-HMS.

 

[cvg]

by "sinks" do you mean a dry lake? If so, cant you treat it as a reservoir and route using stage - storage - discharge relationship?

 

[mlridg]

Thanks for the response. I have thought of that. I could come up with a stage-storage curve but the discharge, if any, is still a question.

 

[queque]

I worked in Nevada (USGS 31 YEARS)and now work in Arizona.
I have found the Maricopa Flood Control District documentation on Hydrology the best yet (10 years) for arid zone application of HEC 1 methodology.
The publication is available for around $40. and includes the most sophisticated software for generatiing the HEC 1 input files.
They can be reached at 602-506-1501.

 

[sam74]

Depending on your application (are you developing pre vs post flow amounts off your site) we typically use the conservative approach and assume that in pre development any drainage area flowing to a sinkhole is completely ignored (no outflow). Therefore, you are lowering your pre developed flow offsite and this keeps your post developed allowable flow offsite to a minimum. If it truely is a sinkhole then infiltration rates are difficult to measure and will be at an ever changing rate as silt clogs the infiltration routes.

We have created storm water injection wells in sinkholes by excavating to the open throat and grouting in a vertical perforated large diameter HDPE pipe and backfilling with 1 foot layers of graded stone separated by a geosynthetic material. In the end the volume of the sinkhole had to be large enough to accomodate the 100-yr, 24-hr storm event runoff amount without overtopping while still assuming no outflow for the same reasons listed above.

An exception we have ran across is when the sinkhole was located close enough to a federally governed body of water such as a lake or river and this governing agency (TVA) had posted flood elevations around the sinkhole on FEMA maps. They had in the past performed dye tests to show that the sink was directly connected to the lake. This superceded the local governments authority and regulations on land improvements involving a sinkhole's watershed.

 

[cvg]

the manual recommended by queque is available in pdf format online at

http://www.fcd.maricopa.gov/Resources/DL/Hydrology Design Manual.pdf

 

[mlridg]

I did look into the Maricopa County Design Manual. I've only browsed through it but if we need to do any further analysis with an alternate method than it will be helpful. I was able to download the pdf, too. Thanks for the suggestions.