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- Lower North Creek SWMA Open House: 2020
Lower North Creek Surface Water Management Area
Open House Recap
City of Bothell held a virtual open house from November 16 through December 31, 2020, as well as a community meeting through Zoom on December 17, to share information with the Bothell community about the Lower North Creek Surface Water Management Area (SWMA). The City's Surface Water staff invited feedback about potential strategies for existing, future, and programmatic efforts and activities within the area that would help protect natural resources.
Response to Community Feedback
Thank you to all who shared feedback with us, either through the online feedback form or during the December 17, 2020 Zoom meeting. Staff appreciate your thoughtful comments and questions. Surface Water staff thoroughly reviewed your feedback and have included responses to those comments and questions that are relevant to this early stage of the planning process.
Recording of December 17 Community Meeting
Surface Water staff held a one-hour community meeting through Zoom to provide background information about Bothell's Surface Water Management Areas and to answer questions about proposed strategies and activities aimed at helping protect water quality. Click here to watch a YouTube recording of the December 17, 2020 meeting.
- About Lower North Creek
- Possible Efforts and Activities
- Data Table for Lower North Creek
- Data Dictionary
General and Physical Character
The Lower North Creek SWMA makes up 3.64 square miles with 65.79 percent (2.40 square miles) within City limits.
Very severely erosive soils also classified on steep slopes (>40%) make up 2.53 percent of the SWMA. Compared to other SWMAs, 2.53 percent is the fourth lowest.
The City had a detailed study of this area performed in 2006, titled the North Creek Fish and Wildlife Critical Habitat Protection Area Study. This study delineated and assessed the importance of wetlands, streams, and other critical areas and their contribution to the quality of cool groundwater inputs to North, Palm, and Woods/Cole Creeks.
Land Use and Development
The prominent land use feature of this SWMA is residential with 36.7% of total parcel area with the second highest land use being commercial with 26.6% parcel area.
Thirty-three percent of the area is covered by impervious surfaces. Of the impervious area, approximately one-fourth of the area is road surface (pollutant generating).
Natural Environment
The area includes two streams (Palm Creek and Woods/Cole Creek) and an area that drains directly to North Creek. The total stream length within the SWMA is 16.96 miles. Twenty-two percent of the SWMA is mapped as wetlands and associated buffers.
The City has assessed habitat and biologic conditions for Lower North Creek at Palm Creek and found it to have the least impaired biological community of all streams in the city, though the creeks are still severely to moderately impaired. All streams in the SWMA are known to have low dissolved oxygen levels and high temperatures and are on Ecology’s 303(d) list for impaired water bodies for fecal coliform.
Stormwater Infrastructure
The amount of total stormwater conveyance is 107 miles (29.39 miles/square mile) with 4,009 catch basins within the SWMA. The SWMA has 26.7 control structures per square mile and 114.4 water quality treatment facilities per square mile.
Surface Water Management Strategies
This SWMA has some of the higher quality basins that support North Creek in Bothell. Staff has selected Lower North Creek as its SMAP high-priority basin. Surface Water efforts will focus on protecting and preserving stream buffers and enhancing stormwater controls to the relatively higher quality creeks in this area.
Existing Development Strategies
- Address any flooding or fish passable issues through project identification and planning
- Seek funding for retrofitting existing systems or creating new regional facilities to enhance flow control and water quality benefits
- Inspect and enforce existing stormwater system maintenance at a higher frequency
Land Management and Future Development Strategies
- Require level three flow control for all new and redevelopment
- Require enhanced water quality treatment for new and redevelopment
- Encourage clustering to reduce impervious surfaces and protect native vegetation
- Map wildlife corridors and work to ensure these are protected
- Reserve green space or identify impervious surfaces that can be converted to green space
- Review for transfer of development rights or zoning changes to protect critical areas
- Review existing codes for ways to encourage preservation of open space
Programmatic Management Strategies
- Identify potential parcels that would benefit from restoration efforts within buffer areas
- Increase monitoring of creeks within area to increase knowledge concerning existing conditions
- Increase water quality sampling within storm system corresponding to creek monitoring to assure early detection of issues
- Focus outreach on residential activities that are impacting water quality such as:
- pet waste
- low impact development installation
- streamside landowners
- Prioritize illicit discharge inspections in this area to protect streams
- Increase business inspection frequency to inspect and enforce best management practices based on use
Lower North Creek Data Table
Click here to view this table as a PDF.
Area | ||
Total Area | sqmi | 3.64 |
Bothell City Portion | sqmi | 2.40 |
Bothell City Portion | % | 65.79 |
Land Use | ||
Single Family Residential | % | 29.67 |
Multi-Family Residential | % | 6.98 |
Total Residential | % | 36.65 |
High Use Commercial | % | 0.00 |
General Use Commercial | % | 21.28 |
Industrial | % | 5.32 |
Total Commercial | % | 26.60 |
Mixed Use (Residential and Commercial) | % | 0.23 |
Active Use Parks | % | 0.00 |
Passive Use Parks | % | 3.18 |
Total Parks and Open Space | % | 3.18 |
Natural Areas (Streams, wetlands, and buffers) | % | 16.13 |
Undeveloped | % | 3.32 |
Right-of-Way | % | 13.90 |
Land Cover | ||
Impervious | % | 33.13 |
Limited Access Roads | % | 3.16 |
Arterial Roads | % | 1.99 |
Local Roads | % | 3.66 |
Total Road Surface | % | 8.81 |
Tree Canopy | % | 46.53 |
Physical Geography | ||
Very Severely Erosive Soils (Class V) on Slopes over 40% | % | 2.53 |
Natural Areas | ||
Wetland Areas | % | 12.51 |
Wetland Area + Buffers | % | 22.39 |
Rivers and Streams | mi/sqmi | 4.66 |
Storm Infrastructure | ||
Pipes and Culverts | mi/sqmi | 22.57 |
Ditches | mi/sqmi | 5.80 |
Bioswales | mi/sqmi | 0.49 |
Trenches | mi/sqmi | 0.53 |
Total Conveyance | mi/sqmi | 29.39 |
Catch Basins | #/sqmi | 1101.38 |
Control Structures (some in vaults, detention ponds, etc.) | #/sqmi | 26.71 |
Detention Pipes | #/sqmi | 9.60 |
Detention Ponds | #/sqmi | 13.36 |
Vaults | #/sqmi | 25.04 |
Filters | #/sqmi | 66.36 |
Total Number of Water Quality Treatment Facilities | #/sqmi | 114.35 |
Pervious Pavement | #/sqmi | 0.00 |
Bioretention | #/sqmi | 1.25 |
Tree Boxes | #/sqmi | 0.00 |
Total Number of LID Facilities | #/sqmi | 1.25 |
Population | ||
Population Density | people/sqmi | 2391.73 |
Data Dictionary for City of Bothell's Watershed Analysis
This guide describes the data values in the results spreadsheet of City of Bothell's watershed (monitoring basin) analysis. The goal is for this analysis to assist in the prioritization of surface water infrastructure improvements among these monitoring basins. This guide briefly describes each value. For a more complete explanation of how each value was derived using ArcGIS Desktop 10.6.1 (advanced license), please refer to the workflow guide at www.bothellwa.gov/swmaworkflow..
It's also important to note that this data dictionary is based on GIS data at coarse scale and is NOT intended to represent a scientific or survey-grade study of drainage or other phenomena. GIS data (maps) are produced by the City of Bothell for internal purposes. No representation or guarantee is made concerning the accuracy, currency, or completeness of the information provided.
Click here to view this table as a PDF.
Data Value | Units | Description |
Area | ||
Total Area | sqmi | The total area of the monitoring basin that is covered by the catchments of tributaries that intersect Bothell's city limits. |
Bothell City Portion | sqmi | The area of the monitoring basin that is within Bothell's city limits. |
Bothell City Portion | % | The percentage of the monitoring basin that is within Bothell's city limits. |
Land Use | ||
Single Family Residential | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Single Family Residential" land use. Single Family Residential: includes houses, townhomes, mobile homes, and manufactured homes. |
Multi-Family Residential | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Multi-Family Residential" land use. Multi-Family Residential: includes apartments and condos where no commercial use on ground floor exists. |
Total Residential | % | Sum of the above two percentages. |
High Use Commercial | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "High Use Commercial" land use. High Use Commercial: includes areas with oil/water separators such as restaurants, gas stations, etc. Oil/water separators are in storm site layers. |
General Use Commercial | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "General Use Commercial" land use. General Commerical: includes office, retail, public facilities, schools, churches, etc. |
Industrial | % | The percentage of the monitoring basin that is within Bothell's city limits that is covered by "Industrial" land use. Industrial: includes sites such as Romac, Philips Healthcare, Seattle Times Printing Plant, etc. |
Total Commercial | % | Sum of the above three percentages. |
Mixed Use (Residential and Commercial) | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Mixed Use (Residential and Commerical)" land use. Mixed Use: includes areas where residential buildings are on top of commercial buildings such as SHAG. |
Active Use Parks | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Active Use Parks" land use. Active Use: includes ballfields, areas with restrooms, playgrounds, etc. |
Passive Use Parks | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Passive Use Parks" land use. Passive Use: includes areas of passive recreation. |
Total Parks and Open Space | % | Sum of the above two percentages. |
Natural Areas (Streams, Wetlands, and Buffers) | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Natural Areas (Streams, Wetlands, and Buffers)" land use. Natural Areas: includes streams, wetlands, and buffers. |
Undeveloped | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Undeveloped" land use. Undeveloped: Use the vacant layer for this category to find areas with potential of future development. |
Right-of-Way | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "Right-of-Way" land use. Right-of-Way: As land use was defined at the parcel level, the "right-of-way" land use fills in the gaps between parcels within the Bothell city limits. |
Land Cover | ||
Impervious | % | The percentage of the monitoring basin within Bothell's city limits that is covered by an impervious surface. This includes all impervious surfaces of roadways (below), buildings, parking lots, driveways, walkways, patios, decks, and miscellaneous. |
Limited Access Roads | % | The percentage of the monitoring basin within Bothell's city limits that is covered by impervious road surface that is part of a limited access highway. This includes I-405, the eastern portion of SR 522, and all associated on-ramps and off-ramps. |
Arterial Roads | % | The percentage of the monitoring basin within Bothell's city limits that is covered by impervious road surface that is part of an arterial roadway. This includes all major, minor, and collector arterials that aren't classified as limited access highways. |
Local Roads | % | The percentage of the monitoring basin within Bothell's city limits that is covered by impervious road surface that is not part of a local roadway. This includes every road that is not classified as either a limited access highway or arterial roadway. |
Total Road Surface | % | Sum of the above three percentages |
Tree Canopy | % | The percentage of the monitoring basin within Bothell's city limits that is covered by tree canopy. This may overlap with impervious surface in some areas. |
Physical Geography | ||
Very Severely Erosive Soils (Class V) on Slopes over 40% | % | The percentage of the monitoring basin within Bothell's city limits that is covered by "very severely erosive" soil (Class V) and is on a steep slope over 40%. |
Natural Areas | ||
Wetland Area | % | The percentage of the monitoring basin within Bothell's city limits that is covered by wetlands. |
Wetland Area + Buffers | % | The percentage of the monitoring basin within Bothell's city limits that is covered by wetlands or their associated buffers. |
Rivers and Streams | mi/sqmi | The density of rivers and streams (including piped streams) within the portion of the monitoring basin within Bothell's city limits. |
Storm Infrastructure | ||
Pipes and Culverts | mi/sqmi | The density of pipes and culverts (including piped streams and detention pipes, but not piped trenches) within the portion of the monitoring basin within Bothell's city limits. |
Ditches | mi/sqmi | The density of stormwater ditches (not bioswales) within the portion of the monitoring basin within Bothell's city limits. |
Bioswales | mi/sqmi | The density of bioswales within the portion of the monitoring basin within Bothell's city limits. |
Trenches | mi/sqmi | The density of trenches (including infiltration, dispersion, and interceptor trenches, and trenches with pipes) within the portion of the monitoring basin within Bothell's city limits. |
Total Conveyance | mi/sqmi | Sum of the above four densities. |
Catch Basins | #/sqmi | The density of catch basins within the portion of the monitoring basin within Bothell's city limits. |
Control Structures (some in vaults, detention ponds, etc.) | #/sqmi | The density of control structures (including those in vaults, detention ponds, etc.) within the portion of the monitoring basin within Bothell's city limits. |
Detention Pipes | #/sqmi | The density of detention pipes within the portion of the monitoring basin within Bothell's city limits. |
Detention Ponds | #/sqmi | The density of detention ponds within the portion of the monitoring basin within Bothell's city limits. |
Vaults | #/sqmi | The density of vaults within the portion of the monitoring basin within Bothell's city limits. |
Filters | #/sqmi | The density of filters (in catch basins, control structures, and vaults) within the portion of the monitoring basin within Bothell's city limits. Filters include oil/water separators. |
Total Number of Water Quality Treatment Facilities | #/sqmi | Sum of the above four densities. |
Pervious Pavement | #/sqmi | The density of pervious pavement installations within the portion of the monitoring basin within Bothell's city limits. |
Bioretention | #/sqmi | The density of bioretention (or rain garden) installations within the portion of the monitoring basin within Bothell's city limits. |
Tree Boxes | #/sqmi | The density of tree box (or Filterra) installations within the portion of the monitoring basin within Bothell's city limits. |
Total Number of LID Facilities | #/sqmi | Sum of the above three densities. |
Population | ||
Population Density | people/sqmi | An estimate of population density within the portion of the monitoring basin within Bothell's city limits. Washington State Office of Financial Management estimates of average household size based on the number of units within a building were combined with the City of Bothell's building and address layers to estimate the population on each address point. Address points that were likely residences were then intersected with the monitoring basins. |