Run-off and landuse change

For my parcel maps that I created, the parcels are number 1-5 from the left to the right.

To make my calculations I first had to set out the percentages of each type of surface that was on my maps. The curve number of grass is .39, for paved areas it is .98, and for impermeable areas like rooves it is 1.00. I multiplied each of these numbers first by the amount of rainfall in each storm, and then by the total percentage that they took up in a given parcel. For example, my formula for the 2 year return 24 hour storm my formula was (r * .39 * g) + ( r * .98 * p) + (r * 1 * i). This gave me an output in total inches of runoff per parcel, per storm.

r = rainfall per storm

p = percentage of parcel that is paved

g = percent of parcel that is grass

i = percent of parcel that is impermeable

All of the land use infiltration rates for my location have gotten worse for each specific parcel over this 19 year period. This is large in part due to an expansion of parking areas. In 1999 my parcels had a bit less paved areas, and a lot fewer people that were parking on grass that would compact it (at least as far as I could tell) One thing to note is that in 2018 on one of my parcels it appeared as though there was more compaction due to frequent walking on. All of the grass was dead, and upon further google earth searching, it was an area that received frequent foot traffic.

In the 1600s when there was lots of forest cover the amount of water runoff would have been a lot lower. Assuming it is all forested the runoff rate would have been steady at .39. Just to compare one of my parcels I will put this number into the formula for one of my parcels. (.39 * 2.3) which equals .897. This is .897 in comparison to the 1.3816 inches that it would be now. Getting rid of our grass, for pavement or packed dirt parking lots is really impacting the infiltration rate of the parcels in Burlington.

Above is all 4 of my graphs displaying the difference in rainfall infiltration for each type of storm.

More runoff from these properties could essentially mean more pollution getting into our larger water sources. Many things can be picked up by the water, like lawn chemicals, garbage, and other things. Those polluters would likely then be transported to a large body of water, in this case Lake Champlain. We are heading towards more and more run off, because We are paving driveways, or just packing them down very tightly with our cars. If these parcels had more grass, there would be more groundwater infiltration and less runoff. Water quality in Lake Champlain will go down, since our runoff numbers will likely continue to go up unless the city of Burlington decides to make some changes.