Data Description
Vashon Island Water Type And Stream Mouth Assessment

Base Data

Water Type Data

Supplemental Data Point Attributes

1. Instream Photograph Points
2. Culvert Points
3. Bulkhead Points
4. Withdrawal Points
5. In-Stream Feature Points
6. Last Fish Points
7. Sediment Source Points
8. Stream Mouth Points

Base Data

Geographic base data for this map set includes the following features: shoreline, roads and water bodies. All of these features were acquired from King County GIS, and were issued in April, 1999. One modification has been made to these sources: the roads layer has been clipped to the extent of the shoreline. This was done so that roads do not appear to extend into Puget Sound, and was done solely for presentation purposes.

Water Type Data

The water type information illustrated in this map set represents data collected in the field by Washington Trout surveyors. All Water Type Data presented in this map set are complete and comprehensive. Streams were typed using the water typing protocol outlined by the Washington State Department of Natural Resources in WAC 222-16-030. Western Washington type designations have the following definitions:

Type

Biological

Physical

Ponds

Human

1

 

Shorelines of the State, rivers with defined channel greater than 20 ft.

 

 

2

Used by substantial numbers of fish for spawning, rearing, or migration.

Defined channel at least 20 ft. wide, with a gradient less than 4%. Or, is used by salmonids for off-channel habitat.

Ponds with surface area greater than 1 acre.

Diverted for use to serve more than 100 residential or camping units, or diverted for a fish hatchery.

3

Used by significant numbers of fish for spawning, rearing, or migration.

Defined channel at least 2 ft. wide, with a gradient less than 16%. If the contributing basin size is greater than 50 acres, gradient may be up to 20%.

Ponds having surface area less than 1 acre at seasonal low water and having an outlet to a fish stream. Or, ponds with a surface area greater than 0.5 acres at seasonal low water.

Diverted for use to serve more than 10 residential or camping units.

4

Waters not used by fish.

Perennial flow, defined channel less than 2 ft. wide.

 

 

5

Waters not used by fish.

Seasonal flow.

 

 

9

Unclassified.

 

 

 

Supplemental Data Point Attributes

1. Instream Photograph Points

Instream Photograph Points represent locations where photographs were taken during the water type survey. The points have been generalized to prevent overlap, and are positioned to reflect the location of what is seen in the photograph, not the location of the photographer. Several photographs can be represented by a single point. These points are hyperlinks and can be clicked to see the photographs that were taken at the specified location.

2. Culvert Points (provisional)

Culvert Points represent locations of culverts on type-2 or type-3 water. Culverts are grouped into two categories. The first category contains culverts that present definite barriers to fish migration. The second category represents all other culverts, including: culverts deemed possible barriers, but not fully surveyed; culverts known to exist, but not surveyed at all (mostly due to access restrictions); culverts that do not present any barrier to fish migration. These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified culvert, where such information is available. All culvert data presented is provisional. No watersheds on the Island were systematically surveyed for culvert information, and the scope of Culvert Points presented in this map set is not intended to be comprehensive.

3. Bulkhead Points (provisional)

Bulkhead Points represent the locations of tidal zone structures that control stream flow. All bulkheads included on these maps represent complete or partial barriers to fish migration. Most of these structures were installed to prevent beach erosion at the mouths of streams. These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified bulkhead, where such information is available. All bulkhead data presented is provisional. No watersheds on the Island were systematically surveyed for bulkhead information, and the scope of Bulkhead Points presented in this map set is not intended to be comprehensive.

4. Withdrawal Points (provisional)

Withdrawal Points represent locations at which water is being removed from a stream. Most of these points represent withdrawals for water supply, either private or public. All of these points are believed to be active withdrawals, and inactive withdrawals have been excluded. Withdrawals can have a dramatic effect on fish distribution by reducing stream flow. Withdrawals and associated structures may also physically block fish migration. These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified withdrawal, where such information is available. All withdrawal data presented is provisional. No watersheds on the Island were systematically surveyed for withdrawal information, and the scope of Withdrawal Points presented in this map set is not intended to be comprehensive.

5. In-Stream Feature Points (provisional)

For this survey, in-stream features are defined as structures, either man-made or naturally occurring, that affect the flow of a stream and/or may present a barrier to fish migration. This definition includes diversions, derelict water withdrawals, controlled channels, and logjams. These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified in-stream feature, where such information is available. All in-stream feature data presented is provisional. No watersheds on the Island were systematically surveyed for in-stream feature information, and the scope of In-Stream Feature Points presented in this map set is not intended to be comprehensive.

6. Last Fish Points

Last Fish Points represent the last fish observed by Washington Trout surveyors while moving upstream. These points are not intended to represent the upstream extent of fish distribution; a water-type survey does not require the continual sampling for fish presence. On Vashon Island, all fish observed at Last Fish Points were coastal cutthroat trout (Oncorhynchus clarki). These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified Last Fish Point, where such information is available.

7. Sediment Source Points (provisional)

Sediment Source Points represent the locations at which sediment or pollutants are being introduced into any given drainage. Most of these points represent landslides, although sewage treatment plants and hazardous waste sites have been included. These points are hyperlinks and can be clicked to see information (including photographs) regarding the specified sediment source, where such information is available. All sediment-source data presented is provisional. No watersheds on the Island were systematically surveyed for sediment-source information, and the scope of Sediment Source Points presented in this map set is not intended to be comprehensive.

8. Stream Mouth Points (provisional)

Stream Mouth Points represent the locations at which streams enter salt water. Each point was evaluated for fish passage, categorizing each as unobstructed, obstructed, or undetermined. Stream mouths that were either fully or partially obstructed, and likely impeded or prevented access to the stream by anadromous fish were identified as obstructed. The nature of each obstructed stream mouth was further characterized as anthropogenic (impassable culvert at the mouth, for example), natural (channel gradients exceeds 20% at the mouth, for example), or both anthropogenic and natural.