City Creek Nature Notes – Salt Lake City

March 14, 2017

March 14th

Flooding of City Creek’s Delta – Part V

1:30 p.m. An early spring arrives; the temperature is in the seventies. The canyon continues to be flooded with walkers, runners and bicyclists during the middle of a workday, and this may be driven in part by the fact that the local university is on spring break. Near mile 0.4, I watch a large raptor soaring next to the high cliff walls on the canyon’s west-side for several minutes, and then it dives into a nesting site in cliff wall. Raptors are known to nest there through mid-June. Although trees continue in their somnolence, insects respond instantly overnight. I estimate 500 Box Elder bugs are active in the first mile. Their abdominal segments are a bright red-orange, and this aids them in locating each other for their many mating orgies that I pass on the road. Gnats are in abundance, the first houseflies appear, and I see the first wasp of the season. I count five butterflies of four different types. The first is a large black butterfly with a white trailing edge, probably a Mourning Cloak (Nymphalis antiopa), and the second mid-size butterfly with black wings and a trailing red-orange band is probably an early Red Admiral butterfly (Vanessa atalanta). A White Cabbage butterfly is seen on the Pipeline Trail. The fourth is the inverse of the Red Admiral: orange-winged with a black trailing edge. These are early hatchlings. The annual butterfly explosion, in which up to one-thousand butterflies can be seen on the road, is several weeks away. One regret that I have from the winter is that despite my searches, I was unable to locate any butterfly or moth cocoons hanging from trees. That is where the butterflies hibernate through the winter.

Near mile 0.4 where the Gambel’s oak forest spreads up the western canyon slope, the oak thicket hides small birds, but I can hear about five distinct calls. Only a robin’s call can be definitely identified. Along the stream, a startled thrush runs under the tangle of a bush’s roots. I jog down the Pipeline Trail. In April and May and after the oaks renew their leafs, smaller migrating song birds can be seen perching on the electrical power lines that parallel the trail, but today, I see none. Below Shark Fin Rock near trail mile 0.5, a mid-sized bird, screened by the trees, calls with a loud “chirp-cheep”. I cannot see it, but from the changes of its calls’ levels, I can tell that the bird is standing in place and rotating around, probably advertising for a mate.

In Thoreau’s “Journal” on March 14th, 1854, he hears a large flock of song-sparrows in the trees. On March 14th, 1855, he sees sparrow tracks in the snow leading to blue curls, a plant that contains dried seeds.

The weather and increased ability to forecast flooding works against City residents’ tendency to forget extreme events. The National Weather Service, the National Soil Conservation Service and the U.S. Geological Survey maintain an extensive system of flood gauge monitors and a sophisticated national flood prediction system, the Advanced Hydrographic Prediction Service, the data from which is publicly available (U.S.G.S. 2017, NSCS 2017, NWS 2017b, 2017c). The NWS regularly publishes probability predictions of annual flooding whenever the snowpack is high (Salt Lake Tribune, April 29, 2011). For example, although 2017 has not resulted in flooding in City Creek, flooding in northern Utah towns like Tremonton fill the news.

When City Creek returns to flood its delta, the waters will find a much changed city. In the 2000s, when the North Temple shopping district was rebuilt at the cost of over $1 billion USD. Since 1983, the business district has seen construction of numerous large buildings on both sides or Main and State Streets, and pursuant with City policy, each has constructed many large underground parking lots. For example, between South Temple and 100 South and State and Main, the entire 10 acre block now contains a multi-level underground parking structure. The same is true between 200 South and 300 South between State and Main. The doors that close off entry to these underground cavities are simple thin roll-down affairs that will not keep flood water out. Although during the 1983 flood, sandbagging kept water out of the then only underground garage, when City Creek again floods the downtown, these underground lots will be susceptible to filling with water, and the economic cost of the next extreme flood – which still can overwhelm the post-1983 increased capacity of the storm water system – will be much higher.

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