The FP Minimum Canopy Cover layer provides the minimum percentage of Canopy Cover Required as outlined in FP Board Manual 1 for use when timber harvest is proposed within 75 feet of the bankfull width (BFW) or channel migration zone (CMZ) on flowing S or F streams or, in the case of exempt 20-acre parcel, harvest proposed within the maximum width Riparian Management Zone as described in WAC 222-30-023. The data in the layer is based on the temperature method which is described in Board Manual 1 and uses location (Eastern or Western WA), the water quality stream temperature classification 16 or 18 degrees Celsius, elevation and equations derived from the nomographs included in the Board Manual. The results provided for Minimum Canopy Cover GIS layer, also referred to as Minimum Required Shade, will produce the same results as using the method described in the Board Manual.   The layer provides the Minimum Canopy Cover only on managed timber land.  The layer excludes federal and tribal lands, as well as some land in the Columbia Plateau which does not support commercial timber.  The layer also excludes lands in the Bull Trout Overlay (BTO) because, as outlined in WAC and the Board Manual, all available shade must be retained with 75 feet of the bankfull width or channel migration zone (CMZ) in the BTO.  Additional information on shade requirements can be found in the following WACs: WAC 222-30-021, 222-30-022, 222-30-023 and 222-30-040.  The information in this layer can be used to ensure post-harvest conditions are in compliance with rules ensuring adequate shade on flowing F and S streams.  The Minimum Shade Required percentage is required, under certain circumstances, to be added to FPA questions 23 and 25, as applicable. 

Information on Methods Used to Develop the Minimum Required Shade values:

A 30 meter LiDAR derived digital elevation model (DEM) was used for the elevations. A coverage for the layer was developed by masking out land that does not fall under Forest Practices jurisdiction (e.g. federal land, reservation land), land that is not suitable for commercial timber production in the Columbia Plateau and land in the Bull Trout Overlay. Minimum Shade percentage values were calculated on all other lands.

The nomograph equations used to derived the Minimum Shade percentage values are as follows:

Western Washington Canopy Cover

16 degrees C (Class AA Water)

x(min. shade %) = (elevation - 3766.9804)/-37.95399

18 degrees C (Class A Water)

x(min. shade %) = (elevation - 2304.3335)/-26.53815

Eastern Washington Canopy Cover

16 degrees C (Class AA Water)

x(min. shade %) = (elevation - 4449.4816)/-21.3118

18 degrees C (Class A Water)

x(min. shade %) = (elevation - 3897.4904)/-21.2454

Since we were unable to obtain the original equations for the nomograph plots found in Board Manual Section M-1, these were “reverse-engineered” directly from the plots themselves. The plots were digitized, then placed over a digital graticule that matched the units of the graphs. X,Y coordinate pairs were collected for the major units of canopy cover (0%, 10%, 20%, 30%, etc) These coordinate pairs were then entered into Excel and a linear regression was utilized to determine the slope and y-intercept of the line. These values were then plugged into the script that generated the attribute data.

Constants used in script:

WEST

CONSTANTS_16 = ["Class AA Water - 16 deg C", 3766.98044293834, -37.9539905826727]

CONSTANTS_18 = ["Class AA Water - 18 deg C", 2304.33349890581, -26.5381464741806]

EAST

CONSTANTS_16 = ["Class AA Water - 16 deg C", 4449.48159090909, -21.3118318181818]

CONSTANTS_18 = ["Class AA Water - 18 deg C", 3897.49045454545, -21.2454545454545]

The FP Minimum Canopy Cover layer provides the minimum percentage of Canopy Cover Required as outlined in FP Board Manual 1 for use when timber harvest is proposed within 75 feet of the bankfull width (BFW) or channel migration zone (CMZ) on flowing S or F streams or, in the case of exempt 20-acre parcel, harvest proposed within the maximum width Riparian Management Zone as described in WAC 222-30-023. The data in the layer is based on the temperature method which is described in Board Manual 1 and uses location (Eastern or Western WA), the water quality stream temperature classification 16 or 18 degrees Celsius, elevation and equations derived from the nomographs included in the Board Manual. The results provided for Minimum Canopy Cover GIS layer, also referred to as Minimum Required Shade, will produce the same results as using the method described in the Board Manual.   The layer provides the Minimum Canopy Cover only on managed timber land.  The layer excludes federal and tribal lands, as well as some land in the Columbia Plateau which does not support commercial timber.  The layer also excludes lands in the Bull Trout Overlay (BTO) because, as outlined in WAC and the Board Manual, all available shade must be retained with 75 feet of the bankfull width or channel migration zone (CMZ) in the BTO.  Additional information on shade requirements can be found in the following WACs: WAC 222-30-021, 222-30-022, 222-30-023 and 222-30-040.  The information in this layer can be used to ensure post-harvest conditions are in compliance with rules ensuring adequate shade on flowing F and S streams.  The Minimum Shade Required percentage is required, under certain circumstances, to be added to FPA questions 23 and 25, as applicable. 

Information on Methods Used to Develop the Minimum Required Shade values:

A 30 meter LiDAR derived digital elevation model (DEM) was used for the elevations. A coverage for the layer was developed by masking out land that does not fall under Forest Practices jurisdiction (e.g. federal land, reservation land), land that is not suitable for commercial timber production in the Columbia Plateau and land in the Bull Trout Overlay. Minimum Shade percentage values were calculated on all other lands.

The nomograph equations used to derived the Minimum Shade percentage values are as follows:

Western Washington Canopy Cover

16 degrees C (Class AA Water)

x(min. shade %) = (elevation - 3766.9804)/-37.95399

18 degrees C (Class A Water)

x(min. shade %) = (elevation - 2304.3335)/-26.53815

Eastern Washington Canopy Cover

16 degrees C (Class AA Water)

x(min. shade %) = (elevation - 4449.4816)/-21.3118

18 degrees C (Class A Water)

x(min. shade %) = (elevation - 3897.4904)/-21.2454

Since we were unable to obtain the original equations for the nomograph plots found in Board Manual Section M-1, these were “reverse-engineered” directly from the plots themselves. The plots were digitized, then placed over a digital graticule that matched the units of the graphs. X,Y coordinate pairs were collected for the major units of canopy cover (0%, 10%, 20%, 30%, etc) These coordinate pairs were then entered into Excel and a linear regression was utilized to determine the slope and y-intercept of the line. These values were then plugged into the script that generated the attribute data.

Constants used in script:

WEST

CONSTANTS_16 = ["Class AA Water - 16 deg C", 3766.98044293834, -37.9539905826727]

CONSTANTS_18 = ["Class AA Water - 18 deg C", 2304.33349890581, -26.5381464741806]

EAST

CONSTANTS_16 = ["Class AA Water - 16 deg C", 4449.48159090909, -21.3118318181818]

CONSTANTS_18 = ["Class AA Water - 18 deg C", 3897.49045454545, -21.2454545454545]