The Benefits & Costs of Tide Gate Upgrades on the Oregon Coast

Introduction

Lacking sufficient data for a traditional benefit-cost analysis, this report combines qualitative data from case studies, interviews, and existing literature with quantitative data fromagency contacts and publicly available sources. The aim is to provide landowners and the public with a comprehensive understanding of the tide gate restoration process and its anticipated impacts, benefits, and costs.

This analysis includes an overview of agriculture on the Oregon Coast and the history of related water management and fish passage regulations. A detailed literature review in Section 3 covers the biological, ecological, social, and economic impacts of tide gates, alongside the potential benefits and costs of their modernization. To deepen this understanding and gauge perceptions of tide gates among public officials and private landowners, ECOnorthwest conducted a series of focused stakeholder interviews. These interviews were designed to gather and validate information on the current condition of tide gate infrastructure, the nature and scale of impacts on land use and environmental health, and the anticipated benefits of upgrades.

ECOnorthwest also analyzed two distinct case studies of tide gate improvements. In partnership with TNC, two sites were selected for this examination: the Winter Lake Tide Gate Project and the North Bank Tide Gate Project. The first case study focuses on the wetland restoration project at Winter Lake, which was designed to improve habitat for juvenile salmon, lamprey, and migratory birds while enhancing water control for local ranchers. This project involved installing an upgraded tide gate system, constructing 40,000 feet of channels, removing three miles of levees, improving four miles of levees, and planting of 120,000 trees and shrubs. Early estimates suggest that the project allows ranchers to extend the grazing season by several weeks and could result in an additional 300,000 juvenile salmon returning annually.

The second case study focuses on the North Bank Tide Gate Project, a 7-foot diameter side-hinge aluminum tide gate with a muted tidal regulator installed in 2023 at mile 7.5 of the Coquille River near the settlement of Randolph. The project site encompasses approximately 40 acres of field and 120 acres of forest. Initiated to improve pasture productivity while enhancing habitat quality for coho salmon, the project balances agricultural productivity with ecological restoration efforts.

Collectively, information gathered through interviews, case studies, and literature reviews, is harnessed towards the development of a framework for assessing the benefits and costs of tide gate upgrades.