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URBAN STORMWATER GUIDELINES AND
BEST MANAGEMENT PRACTICES FOR PROTECTION OF
FISH AND FISH HABITAT
DRAFT DISCUSSION DOCUMENT
Contacts: Barry Chilibeck (666-3765) or Megan Sterling (666-2322)
Revision 4
DRAFT
04/09/01 1
Overview
This paper provides a description of the best management practices (BMP) that
are proposed, as well as implementation criteria to describe the development
situations they could potentially be applied to. The BMPs are general
descriptions specific to the implementation plan. The last section provides
information on the hydrological design criteria best suited for determining
impacts of development and implementation of mitigation through application of
BMPs and for watershed hydrological studies. The references attached provide
many sources for additional detailed examples, design criteria, and construction
details.
Rationale
Since 1993, Fisheries and Oceans Canada has been promoting the protection of
fish and fish habitat through detention of stormwater flows from urban
development areas. Broadly stated, these goals were to limit the 1-in-2 year
post-development runoff to rates equal to the pre-development levels and to
maintain, as closely as possible, the pre-development hydrology and water
quality.
Application, monitoring and research of best management practices, stormwater
modelling and planning processes in the past years have increased our
fundamental knowledge about impacts to aquatic systems from stormwater and
urban development. More focus has been placed on minimizing the effects of
impervious area, management of more frequent runoff events and emphasizing
on runoff reduction through infiltration. Systems that incorporate physical and
biological systems, including soil-water contact, have been shown to have
significant capacity to remove contaminants and pollutants from runoff.
In light of this information and other research, the requirements for what is best,
practically, to protect fish and fish habitat must be updated. An initial priority will
be placed on source control and runoff reduction. This is accomplished by
reducing impervious areas and retention of runoff by infiltration or long-term
storage. Second, greater volumes of total runoff must be afforded treatment to
remove contaminants and pollutants that degrade water and habitat quality.
Smaller, frequently occurring runoff events must be routed to areas where
combined biological and physical processes work to improve runoff water quality.
Third, rates of runoff from events less than 1-in-5 year return periods must be
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detained at greater levels to reduce hydraulic and hydrological impacts to stream
systems and habitats. Given the state of knowledge, these guidelines and BMPs
represent what best protects fish and fish habitat from the impacts of stormwater
runoff.
Description of Best Management Practices
Volume Reduction BMP (VR)
Purpose:
Reduce and mitigate the total runoff volume caused by increased urban
development and subsequent increasing impervious areas, as well as to
maximize the amount of runoff returned to shallow groundwater via recharge.
Guideline:
Volumes from the post-development 6 month/24 hour events from impervious
areas are not discharged and are infiltrated to ground. If infiltration to ground
has been determined by an engineer not to be possible, the rate-of-discharge
from VR BMPs will **be equal to the calculated release rate of the infiltration
system.
Suitable BMPs:
Ground infiltration systems, biofiltration swales or burrows, long-term storage in
constructed wetlands or ponds or through EIA reduction.
Water Quality BMP (WQ)
Purpose:
Mitigate water quality impacts to fish habitat by collecting and treating “first flush”
events of smaller storms and more frequent runoff events from impervious areas.
Guidelines:
Collect and treat the volume of the 24-hour precipitation event equalling 90% of
the total rainfall from impervious areas with suitable BMPs. Rate-of-discharge
will not be greater than required to provide suitable hydraulic retention time as to
maximize the effectiveness of the specific BMP.
Suitable BMPs:
Biofiltration swales or burrows, constructed wetlands, exfiltrating dry detention
pond systems.
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Detention or Rate Control BMP (RC)
Purpose:
To restrict the post-development peak runoff flow rate to that of the pre-
development peak runoff flow rate for selected design return periods.
Guidelines:
Design BMPs so the post-development flows match the volume, shape and peak
instantaneous rates of pre-development flows for the 6 month/24 hour, 1-in-2
year/24 hour and 1-in-5 year/24 hour precipitation events.
Suitable BMPs:
Suitable BMPs include extended dry detention ponds, constructed wetlands or
wet ponds, storage swales.
Implementation
These are general criteria for development and application of best management
practices (BMP):
• BMPs should be based on site and watershed planning processes with
appropriate application based on resource values, site suitability, basin size
and type of development
• BMPs should be ecosystem-based utilizing both physical and biological
processes providing both water quality and quantity benefits
• BMP design is based on existing predevelopment conditions, but should
address cumulative development impacts or societal requirements for
enhancement or restoration of aquatic conditions within a watershed
• BMPs should not be sited or designed with footprint impacts to existing fish
habitat
Unless otherwise determined on a site-specific basis, BMPs should be designed
and implemented in the following priority:
1. Volume Reduction (VR)
2. Water Quality (WQ)
3. Runoff Control (RC)
Below is a guide for selection and targeting of BMPs on a watershed or
catchment level, acknowledging space and infrastructure limitations in
redevelopment scenarios:
Redevelopment BMP Potential Watershed
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Scenario Implementation Coding
Rural Residential to Urban
Residential
(0 - 10 units/ha and IA* < 30%)
VR, WQ, RC
Residential Densification to
Multifamily
(10 - 20 units/ha and IA* < 60%)
VR, WQ
Multifamily to Urban
(> 20 units/ha and IA* > 60%)
VR or WQ
* - impervious area
Due to the wide range of site-specific conditions encountered prior to
implementation of stormwater BMPs, it is important to determine the best BMP
investment for the site characteristics, past and future development history. Note
that the use of volume reduction or water quality BMPs can be functionally
interchangeable, and may be dependent on factors such as location within the
watershed, hydrogeology, topography and proximity to large areas of impervious
area. Use of site specific or local BMPs may be part of a catchment or sub-
watershed plan resulting in layering of BMP types. For example, VR could be
implemented at the lot level (e.g., roof top infiltration via swales) requiring
specific WQ controls at EIA sources (e.g., biofiltration, pocket wetlands at
parking lots, road systems) and RC BMPs at sub-catchment scales (e.g., wet
detention/wetlands at neighbourhood level).
Hydrological Design
• Pre-development rates of runoff from developed and undeveloped sites will
be modelled using public-domain hydrological analysis programs with
continuous simulation (e.g., HSPF or SWMM) or third-party programs based
on these models. The model shall be calibrated in saturated and non-
saturated conditions using 6 months continuous flow data.
• A minimum of 12 month period of site hydrological data will be required
unless acceptable regional data is available (e.g., comparable AES data).
• Single event models are acceptable for preliminary sizing of BMPs,
conveyance systems and post-development conditions if representative
multiple event scenarios are modelled.
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• Without hydrological data or a calibrated continuous simulation model,
assumed peak pre-development runoff flows for the 6 month/24 hour
precipitation event will be 4.0 l/s per hectare areas in the Lower Mainland.
• Volumes and rate-of-discharge for the BMP criteria must be detailed in both
reports, and construction and as-built plans.
References
Best Management Practices Guide for Stormwater, Prepared by A. Gibb, H.
Kelly, T. Schueler, R. Horner, J. Simmler and J. Knutson for Greater
Vancouver Sewerage and Drainage District, 1999.
Continuous Simulation Modelling of Streamflow for Urbanized Mountain Creek,
Canadian Water Resources Association 1995 Mountain Hydrology
Conference, M. Currie, C. Johnston, C. Baisley, J. Friesen, Kerr Wood Leidal
Assoc. Ltd. and T. Barber, City of North Vancouver, 1995.
Effects of Surrey's Storm Water Management Policy on Channel Erosion, K. Lee
and P. Ham, 1985.
Land Development Guidelines: Discussion Paper on Wet Detention Ponds -
Draft, Prepared by Sigma Engineering Ltd. for Habitat Management,
Department of Fisheries and Oceans, 1994.
Monitoring Guidelines to Evaluate Effects of Forestry Activities on Streams in the
Pacific Northwest and Alaska, U.S. EPA, Water Division, EPA/910/9-91-001,
L. Mac Donald, 1991.
Performance of Detention Ponds Designed According to Current Standards, B.
Barker, R. Nelson and M. Wigmosta, 1991.
Stormwater Management Manual for the Puget Sound Basin, State of
Washington, Department of Ecology, 1991.
The Role of Stormwater in Sustainable Urban Development, Proceedings of the
Canadian Hydrology Symposium No. 19-1992, Hydrology: Its Contribution to
Sustainable Development, C. MacRae and J. Marsalek, pp. 372-389, 1992.
Urbanization and the Natural Drainage System-Impacts, Solutions and
Prognoses, The Northwest Environmental Journal, D. Booth, King County
Surface Water Management, 1991.
Urban Runoff Quality Control Guideline for British Columbia, Prepared by Waste
Management Group, B.C. Research Corp. for Municipal Waste Branch,
Environmental Protection Division, Ministry of Environment, Lands and Parks,
1992.