Navigable Rivers in Washington Completed

9722-DGZ - Estimating Physical River-Channel Features for Navigable Streams in Washington - Completed FY2009

Problem - The Washington State Constitution (Article XVII, Section 1) asserts “ownership to the beds and shores of all navigable waters in the state up to and including the line of ordinary high tide, in waters where the tide ebbs and flows, and up to and including the line of ordinary high water with the banks of all navigable rivers and lakes.” In light of this article of the constitution, the Washington Department of Natural Resources (DNR) is interested in a statewide method to begin the determination of whether streams are navigable or not. Currently, DNR has a provisional map of navigable waters based on current and historical documentation on whether navigation has been or not been possible. DNR has requested assistance from the USGS in developing a methodology to incorporate physical channel characteristics in a preliminary, statewide map of navigability.

Objectives - The objectives of this study are (1) to develop a method to estimate the physical channel characteristics related to navigability as defined by DNR from available statewide data; and (2) to apply the method to a statewide study to create a navigability map.

Relevance and Benefits - An important part of the USGS mission is to provide scientific information to manage the water resources of the Nation, and to enhance and protect our quality of life. The navigability issue is important because it helps establish State ownership of the "bed and shore" of rivers. Washington State law does not explicitly define what criteria should be used to determine whether a river reach is navigable or not. DNR has looked to other states for quantitative methods for determining navigability of river reaches and has not found any except for some general guidance for Alaska’s rivers. If the proposed methodology proves valid, it may become a model for other states in the Nation.

Approach

1. The USGS will determine relationships between the independent variables mean annual discharge, mean velocity, and cross-section area and the dependent variables associated with navigable streams.
2. A GIS will be used to extract the mean annual discharge, mean velocity, and cross-section area for stream reaches from an available statewide GIS coverage.
3. Department of Natural Resources will provide a GIS coverage with stream gradients for each of the stream reaches defined by the GIS used in task 2.
4. The USGS will apply the findings of tasks 1-3 and the navigability rating in table 1 to create a statewide navigability map of preliminary classifications of streams.
5. The USGS will verify the navigability map created in task 4 using data from previous studies in which channel widths, depths, and gradients were measured.
6. The USGS will write a report to document the methods used to derive the navigability map and the results of the method verification.