This is an earthcache. There is no physical container. To log the find, answer the questions at the bottom of the page. You do not need to leave the trail or do anything to the creek to log this earthcache. Please observe the posted park hours.
Balch Creek is a small stream that drains about 9 km2 of the West Hills, flowing from unincorporated Multnomah County through the canyon this earthcache brings you to, into a manmade tunnel under the Northwest Industrial area, and out into the Willamette River. This earthcache will bring you to a bridge on the Lower Macleay Trail crossing the creek right next to a scenic small waterfall.
The flow in Balch Creek varies significantly with the weather in its small drainage. Along with wide swings in flow rate, the turbidity of the creek also varies. Turbidity is a measure of how clear the water is, with clearer water being less turbid and cloudier water being more turbid.
Increased turbidity can come from several sources - biological material (such as algae), sediment (suspended mud, sand, etc.), pollution (oil, chemical runoff, etc.), and others. In rivers and streams, natural turbidity from sediment in the water will increase at higher flow rates because higher water levels and faster flow rates cause more erosion.
After storms or during strong snowmelt in the creek's watershed, the water of Balch Creek follows this pattern by becoming cloudier as it picks up more sediment - slowly widening and deepening the canyon over time and adding the sediment to the Willamette River where it will eventually come to rest somewhere along that river, near where it enters the Columbia (like Sauvie Island), or further downstream. Storms may also add sediment load by knocking down trees and large branches, exposing loose soil to the water which gets eroded. Trail maintenance and other construction along the creek may also increase turbidity.
When the water is lower, the sediment load is less and the creek is clearer - except in late summer when very slow flow rates may create nearly stagnant pools for plant life to grow.
To claim a find on this earthcache, observe the turbidity and flow of the creek during your visit and send the answers to the following questions to me in an email or message. Logs may be deleted if answers are not sent.
- How turbid is the creek on your visit? Remember that the cloudier the water, the more turbid it is. Wording like "very cloudy", "moderately turbid", and "clear" are some examples of how you can describe it.
- What is the flow rate of the creek on your visit? Not looking for a specific number, something like "strong flow" or "barely a trickle" is fine.
- What do you think is the relationship between the turbidity and flow rate today? Consider recent weather, erosion rates, the season, and other things you may find relevant.
Feel free to add a picture to your log and/or to discuss your observations in your log, but this is optional. The flow rate and turbidity will change from day to day.
Optional activity at this site:
For those who want to get really into it, at the west (upstream) end of the bridge is a spot where you can approach the water above the waterfall. If you are interested, you can take a sample of the water, let it sit for a while (on site or later at home) for the sediment to settle to the bottom, and then describe the size of the sediment in the sample as well as make an educated guess on how the sediment size you collected relates to the flow rate of the creek.
This activity is optional because while not steeply sloped, the approach to the water is on bare rock that some visitors may not be comfortable with. Rocks may be slippery when wet. Use your best judgement when approaching the water and keep a close eye on children.
Transit:
- TriMet routes 15, 26, and 77 have bus stops within 500 meters (0.3 mi) of the Lower Macleay Trailhead.
USGS resources: