Skip to Content


Willamette & Columbia Confluence

A cache by Seal Rock George Send Message to Owner Message this owner
Hidden : 10/27/2008
1.5 out of 5
2.5 out of 5

Size: Size: not chosen (not chosen)

Join now to view geocache location details. It's free!


How Geocaching Works

Please note Use of services is subject to the terms and conditions in our disclaimer.

Geocache Description:

This is a city park at the point of land that faces the confluence of the Willamette & Columbia Rivers. A paved path is available for most of the walk. A stunning beach walk is necessary for the last few hundred feet.

You are standing just east of the confluence of the great Columbia River and Willamette River. These two rivers meet at this point and sweep towards the Pacific Ocean with an enormous force of nature.

A confluence, in geography, describes the meeting of two or more bodies of water, such as these two rivers. In this case it is the tributary river, the Willamette, joining the major river, the Columbia River.

Your task is:
(1) Read the information below before or during your visit to the site
(2) Post a PICTURE of you, your GPS and the point of confluence behind you!
(3) EMAIL answers for numbers 4 - 7 (below) to the cache owner.
(4) PARK AT N 45 38.781 W 122 45.706 and walk along the paved path to the waypoint listed for this cache. At this main waypoint look at the point of confluence just west of you. ESTIMATE how much wider the Columbia River is at this point than the Willamette.
(5) Look across the river and identify at least ONE way in which man has attempted to hold back the erosion of the riverbanks. EMAIL this to the cache owner.
(6) Walk to waypoint N45 39.033 W 122 45.867 and look for the trees. What has happened to the trees over time? What force has caused this to happen?
(7) Look at the beach and explain why you think the water levels change so much on the beach. What causes the water levels to change enough to leave large debris all over the beach?


The Willamette River is no shrinking violet! It is the 13th largest river by volume in the US. It drains the Willamette River basin, an area that is over 11,500 square miles in area. Where the Willamette River flows into the Colombia, right in front of where you are standing, the average flow is 32,000 cubic feet per second (CFS).

For a sense of natural power, during the peak floods in February of 1996, the Willamette River was flowing at an estimated 460,000 cfs. Look around the area and guess what would have been covered up with raging water!

The Willamette River has been tamed by man through some of the 13 US Army Corp of Engineers dams on its tributaries. Of these 13 dams, 11 produce hydropower! Before the dams were installed, great areas of the Willamette Valley had enormous floods!


The Columbia River is to your North. This immense river drains the Columbia River basin, an area that is made up of over 260,000 square miles. It starts in its headwaters in British Columbia, Canada and rushes to the Pacific Ocean in Astoria, Oregon. Where you are standing now you can see both the Oregon side to the South and North (the island belongs to Oregon) and the Washington side to the North.

The Columbia River’s annual flow rate is around 190,000 cubic feet per second. It actually ranges from 120,000 cfs in a low water year to over 260,000 cfs in a high water year.

The Columbia is also ‘controled’ by humans through dams and erosion control. Dams help prevent flooding, produce power, and have slowed down the velocity of the Columbia River.

The Pacific Ocean:

To learn more about the dams on the Columbia, visit this map showing the dams: (visit link)

To see what different dams look like and view historical photos, visit this site: (visit link)

Information was obtained from:

The Willamette River-Keepers web site at: (visit link)

The Department of Ecology for the State of Washington: (visit link)

Please be sure NOT to post the answers to the trees to the website. You MUST post a picture of yourself at the site or the posting is at risk of being removed.

Additional Hints (Decrypt)

Jrne fubrf sbe jnyxvat, oevat n PNZREN naq gnxr n cvpgher bs lbhefrys!

Decryption Key


(letter above equals below, and vice versa)



278 Logged Visits

Found it 271     Didn't find it 1     Write note 5     Publish Listing 1     

View Logbook | View the Image Gallery of 274 images

**Warning! Spoilers may be included in the descriptions or links.

Current Time:
Last Updated:
Rendered From:Unknown
Coordinates are in the WGS84 datum

Return to the Top of the Page

Reviewer notes

Use this space to describe your geocache location, container, and how it's hidden to your reviewer. If you've made changes, tell the reviewer what changes you made. The more they know, the easier it is for them to publish your geocache. This note will not be visible to the public when your geocache is published.