Tidegate Pipe Sizing Tool

The purpose of this tool is to assist landowners in calculating the size and elevation for replacement tidegated culverts in tidally influenced bays and rivers on the Oregon coast and lower Columbia River. The Tool uses hydraulic calculations to recommend a culvert configuration that best meets state and federal fish passage rules while also taking into account economic and field flooding considerations.

A brief overview of the Tool's intended use and key limitations along with high-level instructions for using the Tool is provided below. Please refer to the User Manual (found in the Docs page) for more information.

Tool use and limitations

This tool has been designed to work for the majority of tidegated culverts on the Oregon Coast and lower Columbia River. There are some situations where this tool should not be used, some of which are listed here. A complete listing of Tool limitations can be found in the User Manual.

Watershed Size The Tool is designed for use on small- to medium-size watersheds where a maximum pipe size of 8 feet will work. Tidegate design on larger watersheds will generally require more extensive engineering and analysis.
Discharge Point The Tool assumes that the tidegate is discharging into a bay, slough, or river channel that is much larger than the pipe diameter and directly connected to ocean tides. It should not be used if the tidegate is discharging into a small, shallow stream or if the tidegate discharges into a channel that has additional tidegates downstream.
Floodplain Landuse and Topography The Tool assumes that good drainage is required, keeping water in the ditches and not flooding adjacent fields. It is not appropriate for use where extensive field flooding is occurring or desired, for instance in a habitat restoration project. Consider using the Manual analysis method for more direct control over the Tool.

How to automatically size your pipe

Begin by starting the Analyze Pipe process and choosing your tidegate pipe location from the Site Selection page. If your tidegate is not shown you may create a new location on the interactive map.

Once a site is selected or created the Tool will take you to the Input page. The inputs needed for analysis at most existing tidegate locations have been precomputed. If your tidegate location is not present, or if not all of the required inputs have been precomputed, you can manually define the parameter values. You should also review all the precomputed inputs to ensure they accurately reflect true site conditions and change them if needed. At a minimum, the user is required to enter a location name and provide a culvert length and preferred material for the primary culvert.

The default option in the Input page Analysis Method section—Automated – Find my best pipe size and elevation—will automatically size your pipe. The tool will simulate a wide range of pipe configurations and will provide a recommended pipe diameter and elevation. Detailed results can be accessed from the Results page. The results can be saved and downloaded as a PDF file which can be used as a basis for a permit application or review by others.

How to analyze a specific pipe configuration

You may also use an additional Tool feature to analyze a single specific pipe configuration at a given site. To access this feature begin the same Analyze Pipe process used to automatically size a pipe. After selecting (or creating) a tidegate pipe location on the Site Selection page and arriving at the Input page, select Manual – Analyze specified pipe configuration from the Analysis Method section. Provide the properties for the specific pipe to be analyzed and continue entering/reviewing all remaining inputs. Note that the Manual analysis method does not perform tidegate sizing optimiation; it only runs the single configuration entered.


In case problems or questions arise, please contact Taylor Larson.

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