North Creek Stormwater Analysis

North Creek is an intensively monitored small stream draining from the East Clayton Neighbourhood in the central portion of the City of Surrey. East Clayton was developed using a variety of innovative stormwater management strategies since 2001. We measured changes in streamflow, water quality, and the benthic invertebrate community in North Creek between 1999 and 2009. Analyses examined statistical trends in timeseries data, as well as indicators of streamflow, water quality, and the benthic inverterbrate community.

The analyses found that streamflow, water quality, and the benthic invertebrate community changed substantially in North Creek since 1999. Some were negative changes to stream condition associated with increasing urbanization, while others were positive changes linked to the use of low impact development measures in the developing catchment.

We found that streamflow as a proportion of precipitation has increased significantly over the study period, even though mean annual discharge has not increased significantly. This suggests that exfiltration galleries and other strategies to infiltrate precipitation into the shallow subsurface drainage system has been effective.Maximum annual stormflow decreased. This is contrary to the established pattern in urban watersheds where increased imperviousness and catch‐basin and pipe systems increase peak stormflows. The innovative stormwater source controls appear to infiltrate precipitation that would typically contribute to stormflow. The benthic invertebrate community became more similar to other urban streams in the region because of the loss of sensitive taxa, and the establishment of taxa tolerant of environmental conditions in urban streams. The data indicate that the benthic invertebrate community is in transition as it responds to changing stream conditions accompanying urbanization of the East Clayton catchment. Taxa richness was lower before 2001, peaked between 2002–2004, and then declined. B‐IBI, a composite measure of the benthic invertebrate community, increased significantly between 1999–2001. The significant increase in B‐IBI was driven by changes in only four the ten component metrics, and specifically by the increase abundance of a single predator taxa – Turbellarian flatworms.

Location: North Creek Watershed, East Clayton Neighbourhood, City of Surrey, BC
City of Surrey Engineering
Raincoast Applied Ecology
May 2011 to Spring 2013
North Creek Data Analysis Report; background document: East Clayton Neighbourhood Concept Plan