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UBC Theses and Dissertations

Stability seeding : experimental testing of a new bank protection technique Tatham, Caitlin


The demand for development near rivers, coupled with changes to the hydrologic regime have resulted in an increase in the frequency of high magnitude flooding events. These flooding events pose a threat to infrastructure. To protect infrastructure along channels, traditional bank protection is installed. These structures prevent natural scour and limit bank migration, which can impair ecosystem function. As an alternative to traditional approaches, we propose a new approach to bank protection. Instead of aiming to control channel shape and form, bank protection should work with the processes that govern channel stability. Recent research has shown that the coarse-tail of a channel’s grain size distribution has surprisingly strong affects on a channel’s stability. This thesis aims to capitalize on this finding, by incorporating the coarsest grains on a channel's bed into a bank protection technique. We call this bank protection technique ‘Stability Seeding’. Stability Seeding consists of placing coarse grains onto a channel's banks. When the channel widens, these grains fall into the bed and promote channel stability. To assess the feasibility of using Stability Seeding as bank protection, proof-of-concept experiments were run using scaled physical models. Three experiments were run; the first used Stability Seeding, the second used Riprap as a traditional method of bank protection, the third experiment was composed of a natural channel without any bank protection. It was found that Stability Seeding dampens bank migration, while still allowing a small amount of natural channel adjustment. As a result, using Stability Seeding requires a larger minimum setback distance than traditional bank protection. However, as Stability Seeding allows for some level of bank migration, it results in less vertical degradation than Riprap. Therefore, Stability Seeding could lessen the chance of buried infrastructure being exposed compared to traditional bank protection techniques. In addition, Stability Seeding allows more morphological variation than traditional bank protection. This variation could allow a reach protected by Stability Seeding to be more ecologically productive than reaches protected by traditional bank protection. The findings of this thesis provide the basis for using Stability Seeding as an alternative to traditional bank protection.

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