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After the Blaze: How Will Rain Affect the High Park Fire Burn Zone?

Larry Selzel

Fire managers working the High Park fire west of Ft. Collins have said Mother Nature is the only one who can truly put this fire out. While many are hoping the state’s monsoon rains will arrive early – others are worried about the problem the rains can bring – flooding and erosion.

KUNC’s Jackie Fortier spoke with Lee MacDonald, a senior research scientist in Watershed science at Colorado State University, to find out how the summer storms will impact the large burn area of the High Park Fire.

Fortier - What is going to happen in the area of the High Park fire when it does rain?

MacDonald - So what is going to happen when you have relatively high intensity rainstorm in high severity areas, that is where all the ground cover has been burned, rainfall rates of even just half an inch an hour are enough to start causing substantial surface runoff and erosion. After high severity fires we see runoff and erosion rates increasing by 10 hundred, even 1,000 times. More so for erosion than for runoff. And then this has a very severe affect on runoff rates and particularly surface erosion and then water quality.

Fortier - Is flooding a concern because of the lack of ground cover in the burn area?

MacDonald - What we’re talking about really is a risk factor, so it’s the combination of high severity fire so you’ve reduced the ground cover and then high intensity rainfalls and nobody can predict what kinds of rainstorms we’re going to get after the fire. If we’re lucky, we’ll have a series of small, gentle storms that will encourage the regrowth and then we won’t have these dramatic flooding events. If we’re unlucky especially in the first one or two years if we get a very high severity rainfall event, then we’re going to get very severe flooding and very severe erosion events. These downstream areas located in or adjacent to the floodplain, that is the areas that are already at risk of flooding are at much much greater risk because of the fire. 

Fortier - Dr. MacDonald, could you give me an idea of a time period as to when we no longer have to worry about erosion.

MacDonald - Typically the first year is often a very dry year, the second year again we have very high runoff and erosion rates and by the third summer after burning usually there starts to be enough cover so the risk of runoff and erosion rate greatly decreases.

Fortier - What can the state do to prevent erosion in the fire area?

MacDonald - Mulching, that is the application of some kind of ground cover, either straw mulch, wood chips, we need to try and maintain as much ground cover on these severely burned areas as possible.

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