Flooding & Erosion - Steep Slopes

Is your slope eroding or hazardous? Every winter some slopes fail in Olympia when conditions cause the soil to move downhill. Sometimes there is only slight movement, other times an entire section of the slope slides downhill. Winter is the typical season for slopes to move because of rainfall saturating the slope. The rest of the year is the time to manage your slope to best protect your property.

Is Your Slope in Danger?

Steep slopes with grades of over 40% are most vulnerable to failure.

Moderate slopes with grades over 10% can fail when impacted by features such as impervious soil layers, springs, seeping groundwater, or past movement.
Slopes with only low-growing, shallow-rooted vegetation are more likely to slump, collapse, or slide when rainfall or other water saturates the ground.

The good news is that slope failure can be minimized by:

Managing your stormwater;
Establishing deep-rooted vegetation; and
Removing excess weight.

Fact Sheet Available:

Review or download our attached "Homeowner's Guide to Protecting Your Slopes" (PDF) and learn more about protecting and stabilizing your slopes.

DVD Available:

For a free DVD on Managing Your Steep Slope with presentations by Ben Alexander of Sound Native Plants; Susan Messegee, Senior Planner, City of Olympia; Craig Tosomeen, Engineer, City of Olympia; and Steve Wise, Code Enforcement Officer, City of Olympia, contact Patricia Pyle at 360.570.5841 or send us an e-mail.

Steep Sloping and Erosion Questions:

If you have additional questions, please email publicworks@ci.olympia.wa.us, or call Craig Tosomeen at 360.709.2737.

Contacting Public Works

Physical Address: 924 7th Ave. SE, Suite A
Mailing Address: PO Box 1967, Olympia, WA 98507-1967 (directions)
Hours: M - F from 8 a.m. to 5 p.m. (except for City-recognized holidays)
360.753.8588, TTY 360.753.8005
publicworks@ci.olympia.wa.us