# Simulating snow melt inundation in urban areas

I am trying to understand how melt water from snow in urban setting gets routed.

I understand that for routing rain water, one can create grid and then determine the flow direction for each cell by using the D8 model. In the D8 model, first the slope for each of the 8 adjacent cells is calculated and then the direction of outflow corresponds to the direction of maximum slope. One can also compute the velocities with some approximations of the St. Venant equation.

I was trying to understand if it makes sense to use this model when :

1. Runoff is because of snow melt in the absence of rainfall.
2. Runoff is generated because of a rain over snow event.

Using the D8 model would mean that, in both of these cases, the snow melts, water percolates down the snow pack, and when it touches the land or water mass, the routing happens according to the current slope values.

Is this a reasonable way to characterize the meltwater flow?

If not, is there any literature where this problem is solved using any alternate technique?

• Wouldn't the slope of the snow often tend to be the same even if it's not percolating all the way downward? Except with the added twist that at some spots windblown/accumulation/piling alterations shift things. But probably a small impact, except when it has been exceptionally windy? Not sure any of those added complexities would be all that easy to account for? Jan 3, 2023 at 21:51
• Why would water from melted snow be different from rain ? Jan 4, 2023 at 16:35
• @blacksmith37 I agree, it won't. What I am not sure if it would be reasonable to assume when snow melts the melt water first moves all the way to the land mass in a downward direction, and once it reaches the land mass then it moves laterally based on the slope? Or does the meltwater creates "paths" within the snowpack, and water moves along those paths laterally? In the later case, the melt water does not need to reach the ground, and flow direction may not be dependent on the ground slopes computed at cell level using the D8 model. Jan 4, 2023 at 16:46
• In an urban setting, there are artificial drainage (storm drains) that may be blocked by snow or slush. Will this affect your routing? Jan 6, 2023 at 14:59
• @SteveSaban I was hoping that if the assumption of melt water first percolating down the snow pack vertically and then moving horizontally is reasonable, then blocking of storm drains by either ice or snow will not lead to inundation. In this case melt water flow will exist beneath the snow pack, which is happening on the ground, and the flow is ultimately leading to the storm drain. Question is if this what really happens - can storm drain be covered on the top by ice or snow, but still carry out its function, of draining the available melt water? Jan 6, 2023 at 18:45