Monitoring Of Impacts On Nagle Creek Wetland From Mica Units 5 And 6

Author: Nupqu Development Corporation

The goal of this current study (CLBMON 59) is to summarize the extent of the Mica 5/6 project-related water level change on the wetland boundaries at Nagle Creek through field sampling and desktop analyses, to determine if there is a significant risk to the wetland habitat. The results of this study will determine the need to conduct future biological inventory assessments in the Nagle Creek wetland area of Revelstoke Reservoir. (BC Hydro, 2011)

The Nagle Creek wetland site can be divided into three different types of wetlands. Each of these wetland types occupies a different elevation zone and they exhibit variation in the tolerance of their member plants to inundation. The wetland subsection W2 (Wm01 – Beaked Sedge-Water Sedge) is most susceptible to be impacted since it occupies the lowest elevation band and plants there will need to struggle the most to adapt to the anticipated water levels.

The Assessment Case predicts substantially more flooded area within the Nagle Creek wetland than currently occurs under the Baseline Case. The W2 wetland segment, which has the lowest elevations, is the most strongly affected with over half the area inundated during the higher water levels (50% Exceedence level or higher). While the current Baseline Case model predicts only limited flooding, and only at the highest water level, the Assessment Case model predicts increases in inundation of up to 61% of W2, 19.6% of W3 and 1.3% of W1 wetland segments

Given the impacts to wetland area, frequency and duration of inundation and depth of flooding, we expect that there will be some shift in the plant species composition and distribution. As was noted during the field visits in 2012, the area of deepest inundation is relatively devoid of plants already. If water levels rise further, a greater area of the wetland will be exposed to similar circumstances.

The Nagle Creek wetland site can be divided into three different types of wetlands. Each of these wetland types occupies a different elevation zone and they exhibit variation in the tolerance of their member plants to inundation. The wetland subsection W2 (Wm01 – Beaked Sedge-Water Sedge) is most susceptible to be impacted since it occupies the lowest elevation band and plants there will need to struggle the most to adapt to the anticipated water levels.

The Assessment Case predicts substantially more flooded area within the Nagle Creek wetland than currently occurs under the Baseline Case. The W2 wetland segment, which has the lowest elevations, is the most strongly affected with over half the area inundated during the higher water levels (50% Exceedence level or higher). While the current Baseline Case model predicts only limited flooding, and only at the highest water level, the Assessment Case model predicts increases in inundation of up to 61% of W2, 19.6% of W3 and 1.3% of W1 wetland segments

Given the impacts to wetland area, frequency and duration of inundation and depth of flooding, we expect that there will be some shift in the plant species composition and distribution. As was noted during the field visits in 2012, the area of deepest inundation is relatively devoid of plants already. If water levels rise further, a greater area of the wetland will be exposed to similar circumstances.