SER Webinar: Invasive Japanese knotweed as a catalyst for streambank erosion

Brian Colleran

Publication Date:

Once established, knotweed s.l. can displace riparian plants, meaning that soil stability once provided by displaced roots is lost, carrying significant knock-on implications for watershed management. We propose that knotweed s.l. rhizomes both displace roots and the structure they provide to soil, and also amplify bank-erosion forces, especially during floods. Further, erosive forces create vegetative propagules, with larger flow events creating larger numbers of propagules and providing the vector for short- and long-distance downstream spread within the watershed. Induced erosion is therefore the main driver of knotweed s.l. invasions along waterways. As some hydrological regimes shift towards more frequent and severe storm events in response to climate change, positive feedback loops may develop in these regions between existing knotweed s.l. populations, sudden riverbank failure, and increased flood-related damage, with presumably significant impacts on riparian infrastructure. While the continued spread of this invasive could have significant riparian flood resiliency consequences if left unchecked, mindful action to control these plants is likely to be beneficial financially, socially, and ecologically within any invaded watershed. Brian Colleran is a Certified Ecological Restoration Practitioner (CERP) and Professional Wetland Scientist (PWS), with a Master’s degree in Natural Resource Management. He has also acquired both the basic and advanced Field Botany certificates from the Native Plant Trust and has worked in several capacities with both state and local wetland laws in Massachusetts. Brian’s career has focused on the restoration and conservation of freshwater habitats, primarily through invasive species and riparian area management. Currently, he is a Principal with Ecological Land Management, and recently returned from Patagonia where he assisted with restoration restoration projects in the Torres del Paine National Park as well as reporting on the southernmost knotweed stands in the world.

Resource Type:

Pre-approved for CECs under SER's CERP program