Indian Creek Drainage Analysis

Client—City of Longview, Washington

Indian Creek is a perennial stream located within the City of Longview’s city limits. An existing road on private property crosses the creek north of Indian Creek Drive with a 24-inch culvert allowing for the passage of normal creek flows. During larger storm events, the road crossing serves as a dam with water backing up in the valley behind the roadway. Gibbs & Olson performed a topographic survey and hydrological/hydraulic analysis to evaluate the capacity of the stream to determine if potential impacts for fish passage and property flooding resulted from removal of the road and culvert. The final evaluation determined that removing the access road and culvert would have significant impacts on the downstream reaches of Indian Creek. Potential flooding was identified at various segments along Indian Creek, and removing the access road and culvert will require additional mitigation strategies to improve the conveyance and capacity of Indian Creek. These strategies include upgrades to the existing driveway and culvert crossings, widening of the existing creek cross sections, and stream bank cleaning to aid in improving conveyance and capacity. The final evaluation recommended two alternative solutions, however, both alternatives will require additional analysis, design and evaluation.