Snow Melt Modeling
Snow Melt Modeling
(OP)
Do any of you have tips to better model Rain on Snow Events for far northern climates? I'll be using probably modified rational or SCS Runoff. Thanks!
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RE: Snow Melt Modeling
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Snow Melt Modeling
RE: Snow Melt Modeling
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Snow Melt Modeling
RE: Snow Melt Modeling
RE: Snow Melt Modeling
RE: Snow Melt Modeling
RE: Snow Melt Modeling
RE: Snow Melt Modeling
Teck Cominco built a 2000 ton per day mine about 80 miles out of Resolute in the mid 70s, so a hospital would be no big deal. From memory , right now I think they make do with a nursing station.
RE: Snow Melt Modeling
The scholars that I have spoken with state it's nearly impossible to try to predict snowmelt flow, mostly due to having too many varying factors. Along with the difficulty of predicting the travel path, travel time, conveyance, etc. under the snowpack there are also a lot of factors that effect the rate of snowmelt:
Current air temperature
Prior air temperatures for last seven days (did it get below freezing at night?)
Ground temperature
Snow pack thickness
Moisture content and density of snowpack
Sun Exposure
Precipitation
So try dumping all of these factors into the already ambiguous calculations to predict basic rainfall and runoff and you might as well throw darts.
I've been trying to figure out how to predict which bridges and culverts may have issues with scour and overtopping during snowmelt and spring runoff by paying attention to the snowpack levels in the adjacent upper drainage basins but it's not even that simple. During particularly warmer weeks in the spring I've seen larger flows in streams when there was less snowpack in the tributary basins than previous years. So rather than concentrating on snowpack I've learned to pay attention to successive daily high and low air temperatures and then react accordingly.
Definitely far from an exact science and not something we can "put in a box" like most engineers like to do.
RE: Snow Melt Modeling
Thanks!
RE: Snow Melt Modeling
The answer to your question depends on the exact purposes of your study (i.e. meeting stormwater regulations, designing a bridge, sizing a culvert, building a detention pond, etc.) and the consequences of system overflow.
From a computational standpoint, you could do something very basic like this:
Assuming that the snowpack contains 10 inches of water content, and the peak snowmelt is 20% in 24 hours, you can estimate a 24-hour smowmelt flow rate based on the snow-covered area. (2" water x snow area / 24 hours, with appropriate units conversions) Add this to your runoff from the superimposed rainfall event to estimate the total flow.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Snow Melt Modeling
RE: Snow Melt Modeling
The general consensus among design engineers is that storm drainage conveyance facilities on the Front Range (Denver, Fort Collins, Colorado Springs - elev. about 5,000 to 6,000 feet) should still be designed based on rainfall and that snowmelt should not be a design factor. But there is also a basic understanding that the higher you go in the mountains the more of a chance that snowmelt becomes the design parameter for predicting runoff, but there are simply not enough studies to reference to even start some sort of snowmelt runoff calculation.
From what I've seen over the last 20 years the storm conveyance facilities in my region that are designed with sufficient capacity to handle flows from a standard 100-year design storm (based on rainfall) have not had any major issues with peak runoff from snowmelt. But I'm also convinced that a snowmelt event that has the probability to occur once every 100 years (a 100-year snowmelt event) will generate a larger flow than the flows from a 100-year rainfall event; again this is specific to my region.
I would think that the UP is more like the Front Range than the Rocky Mountain drainage patterns that I'm observing, so I would be surprised if you really need to worry about snow melt for any conveyance design (but I find it an intriguing challenge to discuss regardless).
RE: Snow Melt Modeling
http://www.fcgov.com/utilities/what-we-do/stormwat...
http://www.wecsa.com/FCClimate/ClimHist.pdf
RE: Snow Melt Modeling
RE: Snow Melt Modeling
There are probably more specific resources, but if you look up RAINFALL FREQUENCY ATLAS OF THE MIDWEST by Floyd A. Huff and James R. Angel. (http://www.isws.illinois.edu/pubdoc/b/iswsb-71.pdf), they look at seasonal distributions of rainfall (not runoff), and Michigan typically receives most of its large storms and precip in the summer. Figure 11 regarding top-ranked 10-day storms by season is pretty interesting. Final thought, maybe someone at the agency regulating stormwater has a "design storm" for a rain on snow event, if that is a criteria they look at.
RE: Snow Melt Modeling
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Snow Melt Modeling
While there may be a "concern" with snowmelt in some Front Range cities, it still has not changed the fact that no engineers on the Front Range design their conveyance systems based on runoff from snowmelt. We can conclude that it's because snowmelt does not generate as much runoff as a rainfall event in most locations along the Front Range, or it may be because it is too difficult to calculate and predict. The recent flooding that took place last fall near Boulder and Fort Collins would probably verify the first conclusion.
But back to the OP's question, I would be very surprised if conveyance systems in the UP are designed with snowmelt in mind.