floods, rivers and a vivid analogy

This is the third in a series of posts from Elizabeth Conner, artist in residency on the Tolt River. Elizabeth is working with scientists who are monitoring the Tolt during flood stage and formulating ways to share the scientific information with the public.


On Sunday Dectoltember 12th 2010, only a few days after I met with two of King County staff members to do some initial planning regarding how I might “shadow” their monitoring work, the Tolt River reached flood stage 4. Since the waters began to rise on Saturday and I knew I would not be able to get in touch with my contacts at King County, I went on-line in an attempt to understand what was going on. It was fascinating to look at numbers and graphs on the King County website, but it also made me realize how much I still do not understand about how rivers work.

While fretting over whether or not I should just leap into my car and head for Carnation, I realized the gutters on my small old house were backing up. Donning rain gear, I climbed a ladder in the pouring rain to remove my personal microcosm of “woody debris” that was channeling water under my already leaky roof. The irony of my gutter-clearing efforts did not escape me. I thought about how much larger an issue heavy rains can be for people who live and work near rivers and pondered how much energy we humans spend trying to keep water from destroying the large and small things we create.

Descending from the ladder, I decided (wisely, in retrospect) to stay out of the way of road crews and continue “watching” the flood situation from a distance. Josh Latterell, an Environmental Scientist with King County’s Watershed and Ecological Assessment Team, explained that staff tasked with monitoring pay attention to what happens at flood stage using “lots of photos from the ground and helicopters, in order to map inundated areas.” However, “it is not safe or feasible to be on and in the river at flood stage.” Additional monitoring efforts take place after flood waters recede and other types of changes can be measured.

 

tolt graph

Following the somewhat disorienting experience of interpreting high water flows on-line, I signed up to receive text message flood alerts from a new automated system provided by the King County Flood Warning Center. On January 13th, I received a text message at 12:17 PM: “the Tolt River is at flood phase 2.” Boots and rain gear now permanently lodged in the back of my car, I was able to catch a ferry from Vashon and arrive in Carnation within 2 hours, just after the Tolt crested, at 2650 feet per second of discharge. Flood phase 2 (out of a total of 4 phases) is already quite impressive. Observing the river from the north bank, I had a fleeting thought that I should add a personal flotation device to the collection of equipment in the back of my car. At the same time, since the Tolt was only at Stage 2 that day, I could see evidence of some expansion of “pilot channels” along the north bank. These channels were constructed as part of the restoration project, to gently encourage the river to expand its floodplain. I made a note to ask about the composition of the sediments deposited during recent floods, since they appeared quite sandy. Josh enlightened me: “The size of sediment tells you about how energy was distributed during the flood. Small particles = low energy = low velocity/fairly quiet water.”

 

tolt graph_2

 

My cell phone chimes, often in the middle of the night, and frequently in series, since I made the decision to receive flood alerts for both the Tolt and the Snoqualmie Rivers, which meet at Tolt-MacDonald Park in Carnation. On January 16th,
1:16 AM – The Snoqualmie River is at flood phase 2…
1:17 AM – The Tolt River is at flood phase 2…
3:45 AM – The Snoqualmie River is at flood phase 3…
11:04 AM – The Tolt River is at flood phase 3.

 

channel_round

 

I asked Josh if this string of text messages might tell a story about why these two rivers sometimes arrive at a particular flood stage simultaneously and then, within a 24-hour period, experience a seven-hour lag. He replied that there are “a number of different possible explanations. The particular hydrology of a watershed is almost as unique as a fingerprint. You could dump the same amount of rain on two basins of the same size, but the floods could be different in size and timing according to differences in the density and branching of the drainage/channel network.” Josh, whose descriptions are vivid and poetic, introduced me to the concept of flood routing by asking me to think of “two different Rube Goldberg devices. The timing of when the marble reaches the end depends on what happens to it along the way.”

 

All photos by Elizabeth Conner