Best Management Practices - Land Development

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4. Water Management

4.1 Water Supply

Subdivisions that create privately owned lots for residential use should be serviced by:

• safe and secure individual supplies of potable water; or
• an approved community water supply and distribution system.

Problems with drinking water quality and quantity have occurred at existing subdivisions on Vancouver Island. Residents typically contact the various levels of government requesting a solution to these problems that are perceived as having been created at the time of subdivision.

Solutions to existing water supply and quality problems are usually expensive. Nearby alternative supplies may not be available. Water supply and treatment facilities may also be expensive to install, operate and maintain.

4.1.1 Water Sources

Best Management Practice - Groundwater

1. The long-term reliability of ground water supplies to a proposed subdivision should be certified by a suitably qualified professional engineer or geoscientist. These professionals should be members in good standing of the Association of Professional Engineers and Geoscientists of BC and have proven knowledge and experience in groundwater development. MELP recommends a hydrogeological impact assessment study be conducted to confirm potential impacts of the water source development on the water supplies of existing adjacent properties and on any nearby surface water resources.
   
   Note: local government may require a subdivision servicing bylaw to implement this BMP.

Best Management Practice - Surface Water

1. If the water supply to a proposed subdivision is to be provided from a surface water source such as a river, creek, lake or spring, then the long-term reliability of that supply should be certified by a suitably qualified professional engineer. The engineer should be a member in good standing of the Association of Professional Engineers and Geoscientists of BC and have a proven knowledge and experience of surface water hydrology and water supply engineering.
2. It is recommended that the water supply and hydrological report confirm that there is an adequate water supply available with detrimental effect on the water supply of other users of the water resource including instream fish flow requirements.
3. Supporting storage and flow control and regulation will be required on most sources of surface water supply, especially on the densely populated east side of Vancouver Island.
4. A licence pursuant to the Water Act is required for the storage, diversion and use of surface water.

4.1.2 Water Licence Requirements

Application for Water Licence

Processing a water licence application includes the evaluation of both water availability and demand. Applicants are required to submit water supply, demand and hydrologic reports that support their proposal and deal with the concerns of other downstream licensed water users, instream fish flow requirements and riparian landowners that may be impacted by flooding or erosion or works crossing their lands.

Many Vancouver Island streams are subject to low stream flows in the summer months. These stream flows are often critical requirements for fish and aquatic organisms. Any water use from these types of streams during low-flow periods must be fully supported by storage. Water may be collected during the high flow winter period and stored for later use during the summer. If the storage is to be developed on-stream, a water licence application should include details of the storage structure.

Existing Water Licences

It is important to note that, if a water licence is already appurtenant to the subject property, the quantities specified should not be used as proof of an adequate potable water supply. Particularly with older licences, there may be low streamflow situations where a water source cannot support regular withdrawal of the quantity of water stated in the licence. Water licences do not guarantee the quantity and quality of water for domestic use.

In many cases, the existing water licences do not reflect the water use requirements of the proposed subdivision. The existing water licence may reflect the intended use on the original parcel but may not support additional use on new parcels.

Best Management Practice

1. If existing water licences are no longer required for the original licensed use on the subdivided land, it is recommended that the landowner abandon these water licences prior to proceeding with the proposed land development.

4.1.3 Community Water Supply and Distribution Systems

In support of subdivision of land, either existing community water supply and distribution systems may be used or extended to service the area.

Existing water systems suppliers able to extend their service, in support of subdivision of land, include:

• municipalities,
• regional districts,
• improvement districts,
• privately owned water utilities and
• publicly owned water utilities.

New water system suppliers may be formed either as:

• local service areas administered and operated by a regional district or as,
• a privately owned water utility.

Privately owned water utilities are subject to the provisions of the Water Utility Act and the Utilities Commission Act. The Comptroller of Water Rights regulates these water systems in the public interest. The requirement to obtain a "Certificate of Public Convenience and Necessity" before construction and operation of a privately owned waterworks system is part of this regulatory process.

A Guide to Applying for a Certificate of Public Convenience and Necessity (CPCN), 1998 is available from the: Utility Regulation Section, Ministry of Environment, Lands and Parks, PO Box 9340, STN PROV GOVT, Victoria, BC V8W 9M1.

4.2 Flood Hazard Management

Each year the Provincial Emergency Program (PEP) of the Ministry of Attorney General, receives many complaints about flooding and erosion concerns including:

 

• threats to the safety and health of people;
• flooding and erosion of property,
• flooding and erosion threatening roads, culverts, improvements, and destruction of aquatic habitat.

Most streams on Vancouver Island exhibit dynamic flow regimes. Winter peak flows can be hundreds of times greater than summer low flows. Any development in the floodplain is at risk. Any development that increases peak flows through stormwater discharge from the subdivision of land or that physically restricts the streams carrying capacity, creates not only risk within the development but also for those properties located nearby or downstream.

Solutions to alleviate stormwater discharge problems created by existing subdivisions may be extremely expensive. One of the best methods for proactive floodplain management is for local government to work with the ministry to develop a floodplain management bylaw.

Best Management Practice

1. It is recommended that land developers fully assess flooding and erosion risk effects to aquatic habitat and to downstream water users from stormwater runoff. Those that increase existing risk or create new high-risk affects to aquatic habitat or to downstream water users should either not be permitted to proceed or mitigate those potential impacts.

4.2.1 Flood-proofing Requirements

The Ministry of Environment, Lands and Parks is empowered under the provisions of the Land Title Act and Bare Land Strata Regulations to consider the risk to life and property from flood hazards.

All subdivision proposals that would likely be subject to flooding currently require referral to a Designated Official of the Ministry of Environment, Lands and Parks (Water Management Program). The designated official shall withhold consent for the proposed subdivision where there is a flood hazard which cannot be practically alleviated, or where development may impede the floodway, or where development is in the path of a major channel avulsion.

Alluvial fans and areas subject to debris flow hazard shall be kept clear of development, unless it can be shown to the satisfaction of a Designated Official of MELP that the potential property damage and the danger to human life is low and that adequate protection can be provided.

Best Management Practice

1. In addition to the protection of property and lives, the potential adverse impacts to aquatic and riparian habitat by changes to streamflow patterns should be prevented.
2. In areas subject to tsunami effects, the potential hazard of a tsunami wave shall be considered when determining flood damage reduction measures. Elevations may be established using recorded events in the area plus a suitable allowance for freeboard.

In order to minimize claims on public funds, minimize damage to property and to warn future property owners of a flooding hazard, covenants are required pursuant to Section 82 of the Land Title Act, and Section 3(3) of the Bare Land Strata Regulations. These covenants are restrictive in nature, containing flood-proofing conditions and a waiver of liability to the province and local authority. These covenants are registered under Section 219 of the Land Title Act on the titles of land subject to flooding at the time of subdivision or on the sale or grant of Crown land. Similar conditions and waivers shall be included in leases or other dispositions of Crown land under Section 8 of the Land Act on land subject to flooding.

Figure 4. Typical Floodplain Cross Section

 

 

 

 

Construction setbacks and levels are required to ensure that new buildings are not damaged by floodwaters and possible erosion. For this purpose, a flood which may occur in any given year, of such a magnitude as to equal a flood having a 200 year recurrence interval is used to determine the designated flood level. The flood construction level is the designated flood level, plus an allowance for freeboard and is used to establish the elevation of the underside of the wooden floor system or top concrete slab for habitable buildings.

Local governments may have to enact floodplain management bylaws to control development within lands subject to flooding. The ministry provides local governments with assistance in developing these bylaws.

Where the flood construction level has not been previously determined, by provincial–federal floodplain assessments and mapping, the following criteria is used:

Where the designated flood flow in a watercourse is estimated to be greater than 80 m³/sec:

1. no building shall be constructed, nor mobile home located within 30 metres of the natural boundary of any watercourse, and;

2. areas used for habitation, business or storage of goods damageable by floodwaters shall be established within any building at an elevation such that the underside of the floor system thereof is no less than the flood construction level where it has been determined by MELP. Where the designated flood level has not been determined, the flood construction level shall be no lower than 3 metres above the natural boundary of any nearby watercourse.

Where the designated flood flow in a watercourse is estimated to be equal to or less than 80 m³/sec:

1. no building shall be constructed, nor mobile home located within 15 metres of the natural boundary of any watercourse, and;
2. areas used for habitation, business, or storage of goods damageable by floodwaters shall be established within any building at an elevation such that the underside of the floor system thereof is no less than the flood construction level where it has been determined by MELP. Where the designated flood level has not been determined the flood construction level shall be no lower than 1.5 metres above the natural boundary of any nearby watercourse.

Where properties are adjacent to the sea (except tsunami hazard areas):

1. no building shall be constructed, nor mobile home located within 15 metres of the natural boundary of the sea; this may reduced to 7.5 metres where the frontage is on bedrock or adequately protected from erosion or through works designed by a suitably qualified professional engineer and a member in good standing of the Association of Professional Engineers and Geoscientists of BC, and;
2. areas used for habitation, business, or storage of goods damageable by floodwaters shall be established within any building at an elevation such that the underside of the floor system thereof is no less than the flood construction level where it has been determined by MELP. Where the designated flood level has not been determined the flood construction level shall be no lower than 1.5 metres above the natural boundary of the sea.

Where properties adjoin lakes, ponds or marsh areas:

1. no building shall be constructed, nor mobile home located within 15 metres of the natural boundary of any lake, pond or adjacent marsh area, or as determined by a site specific assessment, and;
2. no areas used for habitation, business, or storage of goods damageable by floodwaters shall be established within any building at an elevation such that the underside of the floor system thereof is no less than the flood construction level where it has been determined by MELP. Where the designated flood level has not been determined:

1. For lakes over 15 kilometres in length, the flood construction level shall be 3.0 metres above the natural boundary of the lake, or marsh area affected by the lake.
2. For lakes, ponds or marshes that are less than 15 kilometres in length, the flood construction level shall be 1.5 metres above the natural boundary of the lake, pond or marsh area; unless determined otherwise by a site-specific assessment.

On alluvial or coluvial fans or where there are indications of extensive erosion or flooding or terrain instability, specific studies and land use restrictions may be required.

4.2.1.1 Additional Requirements

1. The flood construction level requirements for storage reservoirs; shall be determined on a site-specific basis.
2. The required setbacks and elevations downstream of dams will be determined on a site-specific basis and will include evaluation of the potential risk to people and private property in the event of a failure of the dam.
3. The flood proofing elevation for property immediately upstream of a culvert, under a highway or road shall not be lower than 0.3 metres above the crown of the road, if the culvert has the potential to increase the risk of flood damage.
4. Where tsunamis are a threat on the west coast of Vancouver Island, the flood construction level for properties along inlets or on alluvial fans should be determined by a site specific basis.
5. Any landfill required to support a floor system or pad should not extend within any setback from a watercourse. Structural support or compacted landfill or a combination of both may be used to elevate the underside of the floor system or the top of the pad above the flood construction levels. The structural support and/or landfill should be protected against scour and erosion from flood flows, wave action, ice and other debris.
6. Where a building is legally non-conforming with the flood-proofing requirements set out in any pertinent bylaw, regulation or covenant, provision can be made to allow an expansion of the building at the original floor elevation up to, but not exceeding, 25% of the non-conforming habitable area on the main floor of the building existing at the time of enactment of such flood-proofing requirements. The addition should not increase the degree of nonconformity in respect to setback requirements.
7. Where a building is damaged or destroyed to the extent of 75% or more of its value above its foundations, it can be repaired or reconstructed in conformity with the flood-proofing requirements provided the property conforms to existing zoning.
8. Notwithstanding 8 above, where a building protected by a standard dike is destroyed as above the repair or reconstruction may be permitted at the original floor elevation.
9. Residential flood proofing behind standard dikes may be reduced by the freeboard established by the dike

4.2.2 Geotechnical Assessment

Best Management Practice

1. Where construction would be on land that is subject to or is likely to be subject to flooding, mud flows, debris flows, debris torrents, erosion, and landslip, rockfalls, subsidence or avalanche, the building inspector should require that the owner of land provide a report certified by a Professional Geoscientist registered with the Professional Engineers and Geoscientists of BC that the land may be used safely as intended.