Nelson, B.C., adds inspection policy to mitigate flood and debris risks

In a city traversed by numerous creeks coming down from the mountains it is imperative Nelson, B.C., have a policy to manage and contain one of nature’s wildest forces.

On June 6 the city put its stamp on the Flood, Creek and Catch Basin Inspection Policy — which currently did not exist — to outline procedures for inspection activities on public property to mitigate the risks posed by a flood, debris flood or debris flow.

Arising out of the Steep Creek working group – comprising Development Services, Public Works, Climate and Energy, and Emergency Management – a need was identified for detailed hazard assessments to be completed for creeks in and around the City of Nelson.

“As part of this larger project, a necessary deliverable is a policy and procedure to formalize the creek, culvert and catch basin inspections that Public Works personnel have been conducting for years,” said Colin Innes, City director of Engineering, Capital Works and Special Projects, in his report to council. “This policy, and the inspections, are specific to city-owned property and infrastructure and not intended for inspections on private property.”

Steep Creek hazards include floods, debris floods and debris flows that can cause minor to major damage downstream and are common hazards within mountain communities.

“Several steep creeks have been identified in and around the City of Nelson, giving rise to the need for additional studies to be completed to understand the risk to residents, property and infrastructure fully,” said Innes.

The studies will also influence future development, and emergency planning and align with Nelson Next aspirations.

Looking up

There is a high economic risk attached to some of the creeks that traverse the city’s neighbourhoods, including one tributary that contains a high life safety risk, according to a recent engineering report.

In the Steep Creek Hazard Assessment Report by BCG Engineering out of Vancouver it was found that Cottonwood Creek — with Gold, Selous and Giveout creeks adding to its flows — had the potential for significant economic risk inside the city’s boundaries.

“Given the level of development on the Cottonwood Creek fan we’ve categorized it as high economic risk and do recommend that a detailed hazard and risk assessment be completed in the future, and that that assessment include these tributary creeks for a comprehensive study,” said BCG’s Lauren Hutchinson in her report Jan. 17 to city council on the matter.

The summary assessed four major creeks that affect city residents, with some consideration to creeks such as Giveout — which is susceptible to debris flows with a higher sediment concentration and higher potential forces in places that are developed — that ultimately influence the creeks running through Nelson.

In the Giveout Creek basin there are largely mobile and manufactured homes that are less resilient to impact than a wood-frame or concrete foundation structure, said Hutchinson.

“We’ve identified that there is high life safety risk on Giveout Creek,” she said.

The threat has been communicated to the regional district since the creek lies wholly outside of the city boundary.

In the study BCG looked at creeks running through Nelson with grades more than five per cent (three degrees).

The need

Steep creek hazards such as floods, debris flows and debris floods pose considerable risks to the city and can impact pedestrians, vehicular traffic and residents, particularly during periods of heavy rainfall or snowmelt.

These hazards can also pose a risk to development and infrastructure, as erosion and debris accumulation can cause damage to roads, buildings, and other structures.

The assessment identified that the creeks located within city limits did not pose a life safety risk, however, they do pose an economic risk. BGC Engineering ranked the creeks for further study in the order of priority as: Anderson/Fell Creek; Cottonwood Creek; Smelter Creek; Ward Creek.

“The Steep Creek Assessment report is the first phase of a multi-year project that will result in an increased understanding of local hazards and potential infrastructure upgrades,” noted a City staff report to council.

Cash call

Many sources of funding will have to be sought for projects related to mitigation on the creeks, the BCG summary suggested.

Currently, grant funding is being sought to complete detailed hazard mapping and policy development for steep creeks as part of efforts to reduce the risks and impacts of natural disasters and extreme weather events.

Council has pledged support for applying for detailed hazard mapping for Anderson/Fell Creek through the UBCM Community Emergency Preparedness Fund (CEPF), a program that provides financial assistance to local governments in B.C. to help improve emergency preparedness and response capabilities.

The DRR-CA funding stream can contribute 100 per cent of the cost of eligible activities to a maximum of $150,000 per category.

Timothy Schafer is a Local Journalism Initiative Reporter for the Nelson Daily.