2019-10-28-minutes-public-works-study-session

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nhc Applied to the baseline reach average lateral migration rate of 1.6 feet/year, which was calculated by comparing historic aerial photos (section 3.2), this suggests an increase in the lateral channel migration rate, due to the realignment of Lick Creek, would be about 0.3 feet/year or less. Over a 50 -year period, this equates to about a maximum of 14 feet of additional lateral channel movement compared to an expected baseline of about 80 feet. Due to the dominance of down valley meander migration (illustrated In Section 3.2) most erosion due to this process will be expected to occur within the river's meander belt. Erosion will occur on both banks of the river, depending on the meander alignment, and result in both gain and loss of land in the right bank floodplain. The primary effect of the increased channel migration rate from the addition of flow from Lick Creek would be expected to have a slightly faster cycling of channel occupation within the floodplain. However, the effect of this added flow on the possible expansion of the CMZ over an engineering timeframe (decades to centuries) Is likely to be much smaller. REGIME WIDTH CHANGE In addition to changes In channel migration rates, the impact from a small addition of flow on the regime width of the channel was also evaluated. This was done by applying the concept of Rational Regime Theory, as implemented In the University of British Columbia UBC Regime Model (UBCRM), developed by Millar et al. (2014). Rational Regime Theory provides a useful tool for examining the key factors controlling the channel planform and hydraulic geometry, as well as potential flexibility In the channel form due to natural variability or human -induced changes in water and sediment supply. It Is a robust, physically -based approach to predicting channel dimensions that has been validated against a large empirical dataset (Eaton et al., 2004; Eaton and Church, 2007; Eaton and Millar, 2017). The UBCRM is based on this approach and accounts for many more of the key controlling variables than traditional empirical regime equations, while the required input data is sufficiently limited to be readily applicable. The model utilizes the controlling variables specified below. The model was parameterized with the following inputs: • the same grainsize distribution depicted In Figure 3 (D,OF=72 mm D84=170 mm), • the estimated channel forming discharge for both current and realigned conditions (choice of value described later), • the reach average slope of 0.008, + the default program suggested value of T* = 0.2, • and bank strength (p), calibrated to reproduce the current channel width (as recommended by Eatorw Personas communication 2015). The 2 -rear flow was used as the channel forming discharge for the NF Teanoway River (Q,-849 ds). The calibrated g value was very low (1.01), which is consistent with the observed similarity of the bed and bank material. Bank strength (µ) Is quantitatively defined as the ratio of shear stress required to mobilize the bank material to that required to mobilize the bed material. The calibrated value of 1.01 produced a Potential impact of Erick Creek relocation on the NF Teanaway River Morphodynarnics