Chilliwack Master Drainage Plan

Sep 26, 2012

by SCBC

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Contributors: Community Mapping Network, Glen L. Porter, Dipak Basu, Sara Muir Owen
Location: Lower Mainland, British Columbia
Land Use: Settlement
Habitat Type: Watercourse/Riparian
Project Timeline:

Highlights

The City of Chilliwack is developing a comprehensive Master Drainage Plan to ensure sustainable development and provide future infrastructure savings. Watercourses were mapped using SHIM techniques. By this means, accurate stream locations are now known, and useful stream cross-sections were derived.

Introduction
Challenges
Process
Actions
Results
Next Steps

The City of Chilliwack aims to become a leader in the province with a state-of-the-art integrated drainage system which is technically sound, fiscally responsible and environmentally commendable. To achieve this goal, the City requires a Master Drainage Plan (MDP).

The MDP is expected to provide flood protection, erosion control, water quality improvements, habitat enhancement and ground water protection. As well, it will facilitate prior approval of development projects from senior agencies and minimize costs of future storm infrastructure by economic design of drainage systems based on accurate hydraulic and hydrological data.

The MDP will contribute to the sustainable development of the Eastern Hillsides area of Chilliwack, where conventional drainage practices would be unaffordable and could lead to deleterious consequences for the agricultural lowlands downstream.

Project Objectives
The goals and objectives for the Chilliwack MDP are to:
1. route urban runoff from upland areas through the agricultural lowland to the Fraser River without impacting the low-land community
2. alleviate all existing and potential drainage, erosion and flooding concerns due to the past and future growth in the City of Chilliwack
3. protect streamside resources, including riparian and aquatic habitats, by policies and bylaws
4. remediate existing and potential stormwater quality and quantity problems prior to its discharge to a natural body of water
5. provide infrastructure savings in the future by superior hydrotechnical analysis and by adopting site specific modelling.
Sensitive Habitat Inventory and Mapping (SHIM) procedures using GPS technology cannot provide centimeter-level precision, a SHIM cross-section is not a hydraulic cross-section. Although SHIM procedures do not provide the level of accuracy of an engineering survey, useful stream cross-sections were interpreted from the SHIM data.
The standard Sensitive Habitat Inventory and Mapping (SHIM) procedure involves collection of stream channel wetted, bankfull and floodplain widths and depths. In terms of providing a general description of stream conditions at different points along the stream channel, this is considered sufficient. However, more detailed SHIM field procedures and accompanying mapping software tools have also been developed to capture greater details of stream channel complexity, to aid in development of hydraulic models used for regional flood planning.

Required cross-sectional measurements of stream channel widths, depths and elevations as well as upland riparian features are based on the survey points as shown in the ArcView Cross-Sectional tool. The Cross-Sectional tool is used to graphically display the collected data.
The objectives of the MDP are wide-ranging, so only those actions related to the use of Sensitive Habitat Inventory and Mapping (SHIM) are described here.

SHIM methods and standards were used to map watercourses in the City of Chilliwack. Working with the City, SHIM methods for stream profile cross-sections were refined to produce an acceptable level of detail. Mapping is still being carried out under contract to the City of Chilliwack.

SHIM provides:
- information regarding stream truthing, i.e. legally locating the streams
- stream cross-sections
- riparian forest information
- stream classification
- information on top of bank
- information on in-stream work that may be required
- water quality data — temperature, dissolved oxygen, suspended solids
- streambank condition information
- substrate information.
Council authorized the MDP in 1998. There will actually be three MDPs, the first of which is halfway done with completion expected by 2004. A Draft Action Plan has been completed, and a Policy and Design Criteria Manual for Surface Water Management will be completed in the spring of 2002. The MDP will be integrated into the Official Community Plan (OCP).

The MDP is halfway done. A Policy and Design Criteria Manual for Surface Water Management will be completed this spring.

SHIM mapping provided accurate stream locations, important because accurate knowledge of stream centrelines is essential. Useful stream cross-sections, used to model flow, were interpreted from the SHIM data.

Some endangered species were found and mapped (Pacific Giant Salamander).
Recommendations for the Community Mapping Network:
1. continue to involve all participants, maintain contact, and ensure common objectives by maintaining communication
2. ensure that biologists and engineers have the same understanding of the required watercourse parameters.
Any new SHIM mapping will require new sources of funding to be secured.

Acknowledgements

This case study was prepared by Glen L. Porter (G.L. Porter Consulting) with assistance from Dipak Basu, Peter O’Byrne and John Wiley (all of the City of Chilliwack) and Katrina Roger (Cascade Institute) for the ‘Planning Sustainable Communities Workshop’ sponsored by the Community Mapping Network (www.shim.bc.ca) and the Township of Langley. The workshop, held March 15, 2002, showcased examples of mapping as a tool for sustainable planning. These examples were compiled in the workshop’s summary document ‘Planning Sustainable Communities’ by Glen L. Porter with support from Brad Mason (Fisheries and Oceans Canada); Rob Knight (Ministry of Water, Land and Air Protection); Gretchen Harlow (Environment Canada); and, Kathleen Moore (Environment Canada). These case studies were later added to the BC Stewardship Centre Case Study Library by Sara Muir Owen with support from Rod Silver (Habitat Conservation Trust Fund).