Sylvan Lake Water Levels Assessment and Options
Environment and Sustainable Resource Development Central Region, Operations Division October 2012 TABLE OF CONTENTS
Introduction ...... 1 Objectives and Scope of Assessment...... 1 Sylvan Creek Description ...... 2 Sylvan Lake Advisory Committee...... 4 Current Problem ...... 5
Sylvan Creek Assessment...... 6 MPE Report ...... 6 Sill Elevation ...... 7 Hydraulic Control Location ...... 8 Stage Discharge Curves...... 9 Sylvan Creek Capacity ...... 12 Historic Water Levels ...... 12 Air Photos...... 14 Sylvan Creek Assessment Conclusions...... 14
Options...... 16 Control Structure ...... 17 Upgraded Outlet Channel ...... 18 Maintain Outlet Channel...... 18 Erosion Protection (Armoured Shoreline or Retaining Walls)...... 19 Bioengineering and Natural Buffers ...... 20
Conclusions & Next Steps ...... 21
Bibliography ...... 22
Appendix A ‐ Sylvan Creek Ownership Appendix B ‐ Sylvan Lake Advisory Committee Ministerial Order and Recommendations Appendix C ‐ MPE Engineering Ltd. Outlet Channel Assessment Report Appendix D ‐ HEC‐RAS Model Results Appendix E ‐ Sylvan Lake Air Photos Appendix F ‐ Options Matrix Appendix G ‐ Conceptual Cost Estimates Basis for Options Appendix H ‐ Presentation Slides & Speaking Notes Appendix I ‐ FAQs Appendix J ‐ Comments on Draft Assessment
INTRODUCTION
Sylvan Lake is located approximately 16 km west of the City of Red Deer midway between Edmonton and Calgary. Sylvan Lake is bounded by Gull Lake and the Blindman River to the northeast and by Gleniffer Lake and the Medicine River to the southwest as shown in Figure 1. Sylvan Lake outflows naturally into Sylvan Creek located in the southeast corner of the lake. Sylvan Creek flows 19.4 km east‐southeast where it discharges into the Red Deer River. The lake has a mean depth of 9.6 m and a maximum depth of 18.3 m. The Sylvan Lake drainage area is 150.9 km2 which includes 43.5 km2 lake surface area at a natural spill elevation of 936.7 m and 12.4 km2 of non‐ contributing area in the west and southwest portion of the basin which does not contribute runoff in an average year. The Sylvan Lake mean annual precipitation and evaporation are 515 mm and 685 mm respectively based on a 30‐year climate period from 1960 to 2009. The mean annual net evaporation volume at a natural full supply elevation of 936.70 m is 6,372,000 m3
Sylvan Lake naturally fluctuates as the water quantity entering and leaving the lake varies. Water enters Sylvan Lake from precipitation, surface runoff, and groundwater flow. It loses water through evaporation, outflow from Sylvan Creek, as well as groundwater.
Precipitation, runoff and evaporation vary annually resulting in changing water levels in Sylvan Lake. Water flowing in Sylvan Creek also varies as a function of lake levels. Net groundwater flow into (or from) the lake is not well understood at this time. It is known that groundwater has a significant role with an overall net inflow into the lake. However, there is only a limited understanding of exactly how this varies seasonally and from year‐to‐year.
Lake levels reached record daily maximums for most of 2011 and are again high in 2012. Concerns over the water levels and the role of the outlet channel continue to be received.
Objectives and Scope of Assessment
The objectives of the channel assessment are:
1) Assess the outlet channel to determine its role in lake’s high water levels; and 2) Identify options for water management.
The scope of this work mainly focuses on the outlet channel itself in determining the extent of its role in the high water levels. Options for water management mainly focus on increasing outflow from the lake as well as options to adapt to the high water levels.
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Sylvan Lake Location Sylvan Lake and Sylvan Creek
S ylv an C r Sylvan Lake ee k
Figure 1 – Sylvan Lake Location Plan
Sylvan Creek Description
Sylvan Creek was originally a small, intermittent and meandering watercourse that acts as an overflow for Sylvan Lake, a drainage route for local runoff, and an outlet for the Sylvan Lake sewage lagoons. Over the years, channel improvement1 and realignment projects were undertaken in partnership with the Town of Sylvan Lake, the Cygnet Lake Drainage District, and Alberta Transportation. Realignments and modifications were designed to accommodate the Town’s expansion, the sewage lagoons, road construction, and upland flows through the drainage district. Although these projects were never intended to control the Sylvan Lake water levels, concerns over the condition of the outlet channel and its role in the high water levels continue to be received.
The Sylvan Lake outlet is located on the southeast area of the lake in NW 3‐39‐1‐W5. The initial 125 m of the channel flows eastward towards Highway 20 in a relatively natural state. The channel itself is relatively free of vegetation with a sandy silt substrate and varies from 1 to 2 m wide and 0.3 m deep. It meanders through a shoreline wetland. A large portion of the shoreline wetland on the southeast end of the lake has been infilled in 1993 reducing the original wetland width from about 150 m to
1 The context of the term “improvement” is from a hydraulic capacity or drainage viewpoint.
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its present width of about 35 m. The lake outlet appears to be subject to siltation and degradation which can impede the channel outlet capacity.
Sylvan Creek originally flowed as a meandering creek under and on the east side of Highway 20. The highway was upgraded in 1988 and the bridge was replaced by a 1400 mm culvert. The culvert was installed incorrectly resulting in the lake outflow being directed south along the west side of Highway 20. At this point, the channel becomes a straight and uniform, crossing Erickson Drive 350 m downstream through two 1200 mm culverts. Sylvan Creek continues south along the west ditch of Highway 20 until it reaches a railroad embankment approximately 800 m downstream from the natural outlet.
At the railroad embankment, the channel veers away from Highway 20 at 45o and flows southwest along the railroad embankment for 135 m. From here, the channel then turns 90o to the southeast where it immediately flows under the railroad bridge. This bridge is a wooden structure with the inside piers spanning roughly the width of the active channel. The bridge is about 2 m above the channel bed.
From the railroad bridge, the channel flows southeast for about 100 m where crosses Highway 11A roundabout through a 1400 mm culvert. The majority of the active channel is a few meters wide and 0.6 m deep. The overbank areas are heavily vegetated with grasses and brush.
Sylvan Creek, to about 3.9 km downstream of Sylvan Lake, serves as the Sylvan Lake outlet and flows primarily through developed lands. Development includes residential, commercial, and utility service improvements.
Several observations related to Sylvan Creek:
a) Highway 20 was upgraded in 1988 and the bridge over Sylvan Creek was replaced with a 1400 mm culvert. The culvert was installed with an inverted slope towards Sylvan Lake limiting outflow in the original Sylvan Creek channel; b) As a result of the highway upgrade, Sylvan Creek flows on the west side of Highway 20 in the current channel routing; c) The outlet channel is relatively natural for the initial 125 m prior to entering into the constructed roadside channel; and d) A set of twin 1200 mm culverts cross Erickson Drive and a rise in the channel bottom approximately 800 downstream of the lake outlet exists.
The ownership and responsibility of Sylvan Creek is complicated. The initial 125 m is crown land and, as such, is not normally proactively preserved as water bodies are not normally controlled for naturally occurring events. Crown lands are administered through the Public Lands Branch of Environment and Sustainable Resource Development. Alberta Transportation is responsible for the next 350 m (along the west
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side of Highway 20 including and slightly beyond the twin culverts under Erikson Drive). Environment and Sustainable Resource Development is responsible for the next 650 m reach where the creek crosses the traffic circle at the intersection of Highway 11 and Highway 20. All culverts within this initial 1.1 km reach are owned and maintained by Alberta Transportation. Environment and Sustainable Resource Development is also responsible for the original Sylvan Creek channel immediately to the east of Highway 20. The responsibility for Sylvan Creek is illustrated in Appendix A for reference.
Sylvane Lak Advisory Committee
Concerns have been raised in the past as the lake has seasonally fluctuated. High water levels in 1990 prompted complaints of bank erosion, beach loss, pollution and flooding of downstream agricultural lands in the Cygnet Lake area. To address the concerns, former Minister Klein established the Sylvan Lake Advisory Committee through Ministerial Order 16/92 (Appendix B) in 1992 to recommend solutions. The committee was composed of elected officials from the Town of Sylvan Lake, Red Deer County, two representatives from the five Summer Villages, and the Cygnet Lake Drainage District. Engineering technical support was provided by the department on options, conceptual design, costs, and hydrology assessments. Objectives of the advisory committee were:
1. Provide advice and make recommendations to Alberta Environment on water management concerns at Sylvan Lake; 2. Identify public concerns regarding water management problems at Sylvan Lake; 3. Provide advice into studies of alternatives to be investigated to resolve the water management concerns; 4. Provide communication links between the government agencies, stakeholders, and the general public on the status of the studies and water management activities at Sylvan Lake; and 5. Other matters referred to the committee by the Minister.
Recommendations were made to the Minister in June 1994 (Appendix B). The initial phase of the recommendations was to upgrade the downstream Cygnet Lake drainage system as was completed in 1999 in partnership between Ducks Unlimited and the Cygnet Lake Drainage District.
For Sylvan Lake, the Sylvan Lake Advisory Committee had recommended that a variable level control structure be constructed to control the lake levels with channel improvements to 3.9 km downstream of the lake outlet. Sylvan Lake levels had naturally receded by the time the Cygnet Lake water management improvements were completed. Because the interest in pursuing the lake water management had waned, the recommendations related to Sylvan Lake were not implemented.
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Current Problem
Lake levels in 2011 reached their highest recorded mean daily elevation since records began in 1918. Lake water levels reached a peak 937.308 m on August 11th. High lake water levels increase the rate of shoreline erosion, flood property, increase the amount of damage to infrastructure, and potentially decrease the recreational value of Sylvan Lake.
Levels in 2012 continue to be high although it appears that they have stabilized at the time of the writing of this assessment and lower than previously experienced for the same date in 2011. It appears that the levels were approximately 937.26 m at the beginning of August 2011 and approximately 937.17 m for the same date in 2012.
Sylvan Lake 2011 Mean Daily Elevation 937.35
937.30
937.25 (m) 937.20
937.15 Elevation
937.10 Water 937.05
937.00
936.95 Mar Apr May Jun Jul Aug Sep Oct Nov
Figure 2 ‐ Mean Daily Elevation for Sylvan Lake for 2011
Concerns continue to be raised to the municipalities and Environment and Sustainable Resource Development over the high water levels and the condition of the outlet channel.
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SYLVAN CREEK ASSESSMENT
MPE Report
Upon request by Environment and Sustainable Resource Development, MPE Engineering Ltd. had undertaken an assessment of the outlet channel (attached in Appendix C). The purpose of the work was to identify the location of the hydraulic control point, survey the outlet channel, and produce a hydraulic model using the HEC‐RAS software. The model was to be set up so that scenarios could be developed for future planning purposes.
Figure 3 – Assessment study reach was from the lake outlet to the North side of Highway 11A. The study reach consisted of the upper 1.1 km of the Sylvan Creek channel extending from the Sylvan Lake outlet to the north side of Highway 11A.
Report conclusions were based on the accuracy of the evaluation and the location of the hydraulic control point. Accuracy could be improved with more measured data for various water levels of Sylvan Lake. The work included a survey of the outlet including the model set‐up.
The location of the hydraulic control point (i.e. the channel section that has the lowest conveyance capacity) was concluded to be near the Sylvan Lake outlet at the point of the highest thalweg elevation. This was surveyed to be 936.7 m.
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Sill Elevation
The sill defines the natural spill elevation of the lake outlet and has a significant influence on the outflow of water from the lake. Within the natural outlet, it is the highest channel bed elevation or thalweg controlling outflow from the lake.
The sill elevation was measured in 2012 as part of the MPE Engineering Ltd. report. Previous referenced sill elevations are summarized in Table 1 below. The location of the hydraulic control point was concluded to be near Sylvan Lake surveyed to be 936.7 m. Since 1955, Sylvan Lake water levels has equalled or exceeded the 936.7 m sill elevation 28 out of 58 years or 48 percent of the time.
Table 1 – Reported Sill Elevations for Sylvan Lake (m)
Elevation Date Reference Comments 936.7 2012 Sylvan Lake Outlet – Model Elevation based on the survey as part of the Calibration Report outlet channel assessment by MPE Engineering Ltd. 936.66 2005 Sylvan Lake Water Quality Sill elevation was estimated based on a Assessment and Watershed prepared stage discharge curve (Figure A‐86 of Management Considerations report) by AXYS Environmental Consulting Ltd. 936.74 1978 Sylvan Lake Regulation Study The reported natural outlet was 3073.3 ft (page 11 of report) by Alberta Environment 936.5 1920s Sylvan Lake‐Cygnet Lake Sill elevation was assumed to be 936.5 in the Study Sylvan Lake‐Cygnet Lake Study (1994) based on previous outlet flow measurements on the lake outlet (page 26 and Appendix B of the report) by Alberta Environment
Since 1978, it appears that the sill elevation has been relatively stable. However, a review of the Sylvan Lake – Regulation by Outlet Control hydrology report attached in Appendix B of the Sylvan Lake‐Cygnet Lake Study (1994) provides a strong indication that the sill elevation was historically lower. The stage discharge curve contained in the hydrology report indicates that the sill elevation was approximately 936.5 m based on data collected in the 1920s.
The reason for the apparent increase in sill elevation is not clear. The lakeshore wetlands in the vicinity of the lake outlet have been significantly infilled in 1993e and th upgrading of Highway 20 occurred in 1988. Both of these events are predated by the reported sill elevation of 936.74 m in 1978 and, as such, are not believed to be an explanation why the sill elevation has apparently increased.
It is not clear whether the outlet naturally silted in over the years or more significant events such as ice ridges have caused the outlet to increase. For practical reasons, it can be reasonably assumed that the historic “natural” sill elevation of the Sylvan Lake outlet
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was approximately 936.5 m. Since the reasons for the increase are not readily identifiable, it is also assumed that the increase is due to natural causes (i.e. it has silted in over time or ice had pushed up a ridge).
Hydraulic Control Location
The initial 125 m of the lake outlet is in a relatively natural state. The shoreline wetland has been significantly infilled in 1993 constraining the outlet to a 35 m strip.
Site visits to the outlet channel in early 2011 by department staff showed that the hydraulic control point was upstream of the railway bridge crossing (see Figure 3). This was based on the observation of free flowing water and lack of ponding or backing up of the water at this location. Other observations include:
one of the twin culverts at Erickson Drive was 80 percent blocked; the tail end of the culverts at Erickson Drive were submerged possibly resulting in tailwater control; significant ponding was occurring in the vicinity downstream of the culverts;
The blocked culvert at Erickson Drive was cleared in June 2011 once the condition of the culvert was brought to the attention of Alberta Transportation.
A series of channel improvement scenarios were run using the HEC‐RAS model for the Sylvan Lake outlet (Appendix D). An improvement in channel conveyance capacity is considered when the water flow rate increases for the same lake elevation. Channel improvements scenarios downstream of the initial 125 m were not shown to have any improvements on the overall channel capacity with the exception where the channel improvements were within the initial 125 m. Table 2 identifies the modeled scenarios.
Table 2 – Channel Improvement Scenarios
Aspect Description Conclusions Twin Culverts Twin culverts were removed from the The overall hydraulic capacity of the channel to show the effects of the twin channel did not improve. It appears, culverts on the overall hydraulic however, that the twin culverts may capacity of the channel. become a limiting factor (i.e. the hydraulic control) point at higher flowrates (i.e. ≥ 1.5 m3/s). Rise at 800 m A rise in the channel at 800 m The overall hydraulic capacity of the downstream of the lake outlet was channel did not improve. smoothed to determine if the backwater effect from the channel rise is causing the lake to back up. Smoothing of Smoothing of the channel and applying The overall hydraulic capacity did not channel a lower Mannings roughness improve significantly. coefficient for the constructed portions
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Aspect Description Conclusions of the outlet channel Upgrading the The initial 125 m is improved by Improvement in overall channel flow natural channel lowering the Mannings roughness capacity was observed especially when (the initial 125 m coefficient and lowering the sill the lake was at its lower elevations. only) elevation to 936.5 m
The HEC‐RAS modelling results indicated that the greatest benefit to increase the discharge capacity of the lake were scenarios which focused on improving the conveyance capacity of the first 125 m of the natural outlet between the lake and Highway 20. It is therefore concluded that the hydraulic control point is near the lake outlet within the first 125 m of the natural channel rather than the constructed channel along the west ditch of Highway 20.
The hydraulic control point is significant in that it defines where the overall channel capacity is limiting. Improvements in overall channel capacity should first focuse in th initial 125 m. Channel improvements in other downstream locations along Sylvan Creek will increase the channel capacity in the immediate area of the improvement but will not result in an overall increase in the channel capacity (i.e. the hydraulic control point at the lake outlet is still limiting).
Stage Discharge Curves
A stage‐discharge curve has been produced based on the HEC‐RAS model as shown in Figure 4. The stage‐discharge curve is for Sylvan Lake at the lake outlet where the hydraulic control point is located.
937.5
937.4
937.3
937.2
937.1
Elevation (m) Elevation 937.0
936.9
936.8
936.7 0.00.20.40.60.81.01.21.4 Discharge (cms) Figure 4 ‐ Stage‐Discharge Curve for Sylvan Lake Outlet based on 2012 HEC‐RAS Model Results (s.b. for Cross‐Section Station 1135)
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A historic stage‐discharge curve is shown in Figure 5. This originated from the Sylvan Lake – Regulation by Outlet Control hydrology report attached in Appendix B of the Sylvan Lake‐Cygnet Lake Study (1994). A review of Figure 5 suggests something has changed in the outlet flow capacity. The curve for 1991/92 indicates poorer performance in the channel than the pre‐1988 curve at lake elevations below about 937.05 m. However, the curve for 1991/92 indicates better performance in the channel flow capacity than the pre‐1988 curve for lake elevations above about 937.05 m.
Figure 5 – Stage‐Discharge Curves for Sylvan Lake for 1991/92 Data and for Data Collected Previous to 1988 copied from the Sylvan Lake – Regulation by Outlet Control contained within the Sylvan Lake‐Cygnet Lake Study (1994) The 2012 stage‐discharge curve (Figure 4) closely agrees with the 1991/92 stage‐ discharge curve in Figure 5. This suggests that the outlet has been relatively stable since 1991/92.
The reason for the improved performance at the higher lake levels and poorer performance at the lower lake levels is not evident. Several known events have occurred in the past which has potential to impact the channel flow capacity. These are further considered below.
Sill Elevation: the sill elevation appears to have increased over time. While it is has been relatively stable since at least 1978, it is evident from Figure 5 that the sill elevation was about 0.2 m lower in the 1920s. Increasing the sill elevation would have a significant effect on the stage‐discharge curve as the lake would have to be about 0.2 m higher before flow would start.
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Shoreline Wetland Infilling: a review of previous photographs and air photos suggests that the shoreline wetland was approximately 150 m wide compared to its current width of approximately 35 m.
The flow through the wetland portion would be quite low because of the heavy and dense emergent vegetation which would significantly impede water flow. As such, the wetland itself is not expected to represent a significant portion of the overall channel capacity compared to the more defined and formed natural channel.
Infilling of the shoreline wetland occurred in 1993. The historic stage‐discharge curve shown in Figure 5 predates the infilling of the wetland. The stage‐discharge curve shown in Figure 4 is from 2012 or 19 years after the infilling. The 1991/92 stage‐discharge curve matches closely to the 2012 curve suggesting that the infilling has not had a significant impact on the overall channel capacity.
Highway 20 Construction: the present alignment of Highway 20 was completed in 1988 which included replacing the bridge over Sylvan Creek with a culvert. The culvert is inverted resulting in the creek to be routed along the west side of Highway 20 whereas it previously flowed under the bridge and along the east side of the original Highway 20.
It is believed that the routing of Sylvan Creek along the west side of Highway 20 resulted in an improvement in channel conveyance capacity when the lake is at its higher levels (i.e. lake levels above about 937.05 m). The Sylvan Creek conveyance capacity between Highway 20 and Highway 11A was improved by re‐routing the stream along the west ditch of Highway 20. The current channel is straighter, shorter, smoother, has a slightly greater slope and is relatively maintained resulting in improved conveyance capacity compared to natural conditions.
Twin Culverts at Erickson Drive: the culvert crossing at Erickson Drive is not considered the hydraulic control point and, as such, does have an impact the lake water level. These culverts do not have any effect on the overall channel capacity and are not considered relevant to providing an explanation why the stage‐discharge curve has historically changed.
In consideration of the above, the most plausible explanation is a combination of a higher sill elevation (compared to the historic sill elevations established in the 1920s) with the improved channel flow characteristics in the constructed portion of the channel. The historic sill elevation was lower resulting in at least some flow at lake levels between 936.5 and 936.7 m whereas currently, lake levels must exceed 936.7 m before water will begin to flow out of the lake. Once flow is established in the constructed portion of the channel, it would have better flow characteristics than the natural original channel.
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Sylvan Creek Capacity
The 2012 stage‐discharge curve shown (Figure 4) indicates that the capacity in Sylvan Creek increases with increasing water levels. Sylvan Creek was estimated to flow at a flowrate of 1.23 m3/s when the lake reached its historic record maximum elevation of 937.308 m on August 11, 2012.
AXYS Environmental Consultants Ltd. estimated the water balance for Sylvan Lake for the period 1956 to 2000 (Table A‐17, page A‐116). Total inflow averaged 34,200 dam3/year (note: a dam3 = 1000 m3) but at the same time, total outflow in Sylvan Creek averaged at 1,600 dam3/year. Evaporation accounts for 95 percent of the water leaving the lake with Sylvan Creek accounting for the balance.
A Cool wet spring is believed to be the most significant factor in the high lake levels in 2011. Sylvan Creek has a limited carrying capacity. This is a natural limitation of the creek and should not be considered an abnormal process. It is also recognized that groundwater may be a significant inflow component into the lake.
Historic Water Levels
Sylvan Lake water levels have been continuously recorded since 1955. From 1918 to 1930, records were sporadically kept. No records were kept between 1931 and 1954 except for miscellaneous readings (see Figure 6).
Since 1955, water levels ranged 1.3 m between the recorded low value of 936.05 observed in 1964 and the recorded high water level of 937.308 m observed in 2011.
Since the mid‐1960s, Sylvan Lake has been experiencing a water level trend increase. The annual maximum daily water levels were 936.80 m in 1974, 937.09 m in 1992, and 937.31 m in 2011. Similarly, the annual minimum daily water levels were 936.05 m in 1964, 936.13 m in 1979, 936.26 m in 1990, and 936.34 in 2004. These suggest an increasing trend in the water levels since the mid‐1960s.
It is not clear if any particular event occurred that is causing the lake levels to steadily increase over the past 50 years. Data trends alone are not conclusive evidence whether the outlet channel has been affected or is otherwise not operating properly.
The historic annual precipitation for Sylvan Lake is shown in Figure 6 for the period between 1960 and 2010. This is based on gridded precipitation data which has been gapped filled from nearby climate station records using inverse distance weighting (IDW) or inverse distance square. This analysis was made to better understand if there were any climatic relationship between precipitation and water levels.
Although the results in Figure 7 suggest the annual precipitation is experiencing a slight decreasing trend, this is not considered significant given the large variation normally in annual precipitation.
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937.4 937.3 937.2 937.1 937.0 936.9 936.8 936.7 936.6 Elevation (m) Elevation 936.5 936.4 936.3 936.2 936.1 936.0 1910 1930 1950 1970 1990 2010
Year Figure 6 – Historic Sylvan Lake Water Levels
Figure 7 ‐ Annual Precipitation for Sylvan Lake
In summary, it appears that there is an increasing trend in Sylvan Lake water levels but the data timeframe may not be sufficiently long to identify if there are any anthropogenic causes or whether it is a natural occurrence. Available precipitation data does not indicate that it is a result of increased precipitation.
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Air Photos
The Sylvan Lake outlet has been historically photographed (included in Appendix E). Conclusions reached by review of the photos indicate:
a) The shoreline wetland was originally approximately 150 m width. b) The wetland appears to be very dense and emergent vegetation. c) A defined and relatively straight outlet channel was evident in all photos reviewed. The lake outlet has been relatively in place since at least 1949. d) Infilling of the wetland beginning in 1993 confined the shoreline wetland to approximately 35 m width. e) The original Sylvan Creek meandered across Highway 20 in a meandering and relatively natural channel.
Sylvan Creek Assessment Conclusions
The following conclusions have been reached based on this assessment:
The hydraulic control point is 15 m downstream of the Sylvan Lake outlet (Station 1135) within the first 125 m of the natural channel reach between Sylvan Lake and Highway 20. Any improvement in overall channel capacity needs to focus on the hydraulic control point since improvements downstream will not increase the overall carrying capacity of the channel (i.e. there will be improvement in the vicinity of the upgraded channel but the channel is still limited at the hydraulic control point). The sill elevation has been relatively stable since at least 1978 but appears to have been historically lower by about 0.2 m. No explanation is available for the apparent change in sill elevation. It is not believed to be a result of the Highway 20 road construction in 1988 or the infilling of the shoreline wetlands in 1993. The capacity of the existing constructed channel is better than the historic natural channel capacity for lake elevations above about 937.05 m but worse than the historic channel capacity for elevations lower than about 937.05 m. Although the reasons are not clear, it is believed that a combination of a higher sill elevation and improved downstream drainage is the most likely explanation. Improvements to the channel downstream of the natural outlet (i.e. smoothing of the channel, removing of the twin culverts at Erickson Drive, removal of the rise at 800 m downstream of the lake outlet) will not result in overall improvement in channel flow. The condition of the lake outlet is in relatively natural condition for the initial 125 m and has an improved carrying capacity for the constructed portion of the outlet channel.
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High water levels observed in 2011 are believed to be a result of cool wet spring decreasing the evaporation rate normally observed at the lake. Groundwater is believed to be a significant flow contribution in the lake. The change in the stage‐discharge curve from the pre‐1988 to the current 2012 stage‐discharge curve is a natural progression of the lake evolution. This is assumed in the absence of any identified specific event or human influence.
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OPTIONS
Options to manage water levels focus on decreasing inflow, increasing outflow or adaptation within the lake itself. Decreasing inflow into the lake would be to divert water from entering the lake. Notwithstanding the economic feasibility of this, options focusing on decreasing inflow were not considered environmentally defendable as they would have significant long term negative impacts on lake levels once the levels return to average or below average levels.
Options for increasing outflow generally focused on the outlet channel. Options to enhance evaporation are not realistic. Aggressively pumping water from the lake could achieve greater control on lake levels; however, this is not considered economically viable. A pump station plus ancillary delivery mechanism could be in the order of $5 to $20 million depending on the full scope of conveyance needs. As such, options for aggressively drawing down the water levels were not considered further.
Options that were considered and presented include:
‐ constructing a control structure; ‐ upgrading the outlet channel; ‐ maintaining the outlet channel; ‐ shoreline erosion protection; and ‐ natural buffers.
The first three options focus on the outlet channel whereas the last two options focus on adaptation to the high water levels within the lake itself. The Sylvan Lake‐Cygnet Lake Study (1994) evaluated conceptual level design and cost estimates for controlling water levels in Sylvan Lake (Section 5 of the report). These were reviewed and included in the above options as they are still considered generally viable. As such, much of this earlier work has been reviewed and adopted here.
For any of the options identified, regulatory issues and approvals will still need to be satisfied. Environment and Sustainable Resource Development does not promote any particular option and presents them for the consideration by the municipalities. Selection and implementation of any particular option is up to the municipalities. Any alteration of the outlet, with an intended purpose of affecting Sylvan Lake levels, is of concern from an environmental perspective because of the potential to affect water quality, fisheries, aquatic vegetation, shoreline vegetation, waterfowl, and other wildlife using the lake or shoreline. The proposed alternatives must be evaluated in terms of their potential to affect these parameters as well as determine the impacts to directly affected downstream landowners. The passage of spawning pike downstream to Cygnet Lake and the return of spawners and young of the year pike to Sylvan Lake is a significant and key consideration.
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These are presented as conceptual options. Further refinement would be required to increase the accuracy of the cost estimates and finalize the design basis for any of the options. The cost estimates are very conceptual and should be considered as order of magnitude costs. Design requirements would also need to be refined.
Finally, the efficacy of these options is generally known but would benefit by further evaluation. A water balance model for Sylvan Lake is currently being finalized that would be used to evaluate the long term benefit of various options.
Appendix F provides a summary table for each of the following options discussed.
Control Structure
This option is based on Alternative “B” as identified in Section 5.2 of the Sylvan Lake‐ Cygnet Lake Study (1994) report. The description here is a reflection of this earlier work but updated to 2012 dollars and a slightly adjusted scope of work.
This option includes the construction of a manually operated control structure. The overflow elevation would be adjusted by removing or placing wooden stop‐logs. Typically, stop logs are removed when lake levels are high allowing higher water flow rates leaving the lake. Once the lake levels reach optimum levels, stop logs can be replaced thereby reducing or stopping outflow from the lake. It is anticipated that the sill elevation of the control structure would be lowered to approximately 936.5 m closer to what is assumed to be the historic natural lake outlet conditions.
The control structure would increase the outflow from the lake. As such, channel improvements downstream of the lake outlet are needed. Increasing the channel capacity also requires upgraded culverts to avoid downstream flooding and erosion.
Key features of this option are that it provides a control mechanism for the Sylvan Lake outlet. The range of lake level fluctuations is reduced which should enhance shoreline stability. Fish egress from the lake is reduced.
However, a detailed operation and maintenance plan is required necessitating agreement with a number of stakeholders around and downstream from the lake. Public perception of mismanagement will likely persist or increase with the installation of an outlet control structure as there will be an expectation of greater control over high and low water levels. Increased flows to Cygnet Lake may exacerbate downstream flooding issues and a control structure will significantly impair the ability for pike to spawn and return from Sylvan Creek.
This option includes restoring Sylvan Creek to its original (pre‐1988) channel with upgrades as identified in the Sylvan Lake‐Cygnet Lake Study (1994).
The (very) conceptual cost estimate for this option is approximately $1,700,000. The components considered as part of this cost estimate are included in Appendix G.
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Upgraded Outlet Channel
The level of Sylvan Lake can be adjusted by a control structure (as described in the previous option) or it can be allowed to naturally fluctuate and still release through an upgraded outlet channel. This option involves upgrading the natural portion of Sylvan Creek but does not include channel improvement downstream of the initial 125 m of the outlet channel. The channel improvements associated with this option is relatively minimal compared to a control structure. It is somewhat comparable Alternative “A” identified in Section 5.2 of the Sylvan Lake‐Cygnet Lake Study (1994) but with a reduced scope of work.
Because this option does not include a level control structure, the lake levels will still naturally fluctuate. This option includes lowering the sill elevation to an elevation 936.5 m which is assumed to be close to the historic sill elevation according to the pre‐1988 stage‐discharge curve.
The key feature of this option is that it is intended to represent the “natural” outflow capacity at a relatively low cost for construction and operation & maintenance. Once a water balance for Sylvan Lake is complete, the overall change to long term lake levels can be quantified. This option is still expected to improve the overall hydraulic capacity of the channel for lake levels at or lower than 937.05 m which, in the long term, will likely have an overall lowering of lake levels. The upgraded channel should not be an impediment to fish movement. As such, pike spawning habitat potential is maintained.
This option also has a more simple operation since the lake will continue to fluctuate naturally. However, perception of mismanagement of water levels will likely continue during extreme high and low events. Increased flows to Cygnet Lake and impacts to downstream landowners will need to be assessed and requires extensive consultation and potentially greater water management complexity between Sylvan Lake and Cygnet Lake.
The full extent of downstream channel upgrades will need to be assessed which may increase the scope of work and costs involved.
The work for this option includes straightening the outlet channel for the initial 125 m, lowering the sill elevation by 0.2 m, and procuring the necessary regulatory authorizations. A (very) conceptual cost estimate for this is $100,000. The basis for this cost estimate is included in Appendix G.
Maintain Outlet Channel
This option is similar to the existing system. Sylvan Lake will continue to naturally fluctuate and no significant modification or changes are proposed to the channel. The initial 125 m of the lake outlet would be straightened and vegetation or debris would be
Sylvan Lake Water Level Assessment and Options Page 18 of 22 October 2012
removed to ensure unobstructed flow. The sill elevation would remain at 936.7 m (i.e. the current sill level).
Key features of this option are that the channel capacity will be maintained with relatively minor channel upgrades. Upgrading when the lake is high may involve the harmful alteration, deterioration or destruction of fish habitat. It may be a consideration to implement this option once the lake levels recede to below the current sill elevation.
This option will not likely to have a significant impact on the lake levels as the overall channel capacity does not change. Regulatory approvals are still required.
A (very) conceptual cost estimate for this option is $50,000. The majority of the cost is based on procuring the necessary regulatory federal and provincial authorizations and may decrease if the lake levels drop below 936.7 m. The basis for this cost estimate is included in Appendix G.
Erosion Protection (Armoured Shoreline or Retaining Walls)
Erosion protection focuses on protecting the shoreline and infrastructure from damage using rock armoring of the shoreline or vertical walls. The previous options focused on increasing or maintaining the outflow from the lake. The following options focuses on adapting to the high water levels.
A key feature of the armoured shoreline option is that they offer good protection for toe and upper bank erosion without the need of a professional engineer. The protection is effective immediately upon installation and no establishment period is necessary although shoreline armouring normally requires the establishment of vegetation as part of the approvals needed. This may offset the need to provide fish habitat compensation. The armouring heals well during rock displacement or movement. It is relatively easy to install and repair.
Placement of rock is usually limited to when the lake is ice covered. A conceptual cost estimate ranges from about $10,000 to $15,000 for a 20 m wide lot. The cost would be borne by the lot owner. The basis for this cost estimate is contained in Appendix G.
Retaining walls utilize steel sheets, concrete walls, or large stone to produce a vertical flat‐faced wall. This option is useds les commonly compared to shoreline armouring but does provide good protection for toe and upper bank erosion. Protection starts immediately after installation (no establishment period) and this type of option may fit into enhanced yard landscaping.
Retaining walls involve considerably greater construction considerations and will require a professional engineer to design and to procure the necessary regulatory approvals. It involves higher maintenance cost than shoreline armouring and rock stabilization may
Sylvan Lake Water Level Assessment and Options Page 19 of 22 October 2012
need to be placed at the toe to prevent undermining of the vertical wall. Vertical walls tend to deflect energy rather than dissipating it potentially resulting in erosion problems on neighboring properties. Fish compensation is necessary as there is a loss of fish habitat.
Bioengineering and Natural Buffers
Bioengineering incorporates plants in combination with natural materials (i.e. logs, stakes, brush bundles) to create a more stabilized soil to resist bank erosion. A feature of bioengineering methods is a self‐repairing shoreline that stabilizes soils, minimizes erosion and contributes to a healthy habitat.
Although bioengineering methods may take various forms, a common feature would be to fix natural materials on the eroding shoreline. The Bibliography provides several references for bioengineering methods with many more available on the web. A key feature of the bioengineering methods are that they grow stronger with age, they are relatively low cost compared to shoreline armouring or retaining walls, they have a natural appearance, and have the benefit of enhancing fish habitat. Some of the disadvantages are that they have no influence on lake level fluctuations and they may take a considerable amount of time before vegetation is effective. Bioengineering methods may take the longest to establish and vegetation failure would be highest initially and when water levels are high.
Natural buffers are setback distances to allow erosion to occur from fluctuations in the water levels. Natural vegetation is encouraged on the buffers. This is considered a low cost option and can be aesthetically pleasing. This option promotes good fish habitat, no lake level control is necessary, and the natural vegetated banks heal and repair themselves. Vegetated banks may be viewed as unsightly as trees and shrubs fall in and it may take a considerable establishment time before vegetation is effective. There will be a higher vegetation failure rate initially especially if the lake levels are high.
Sylvan Lake Water Level Assessment and Options Page 20 of 22 October 2012
CONCLUSIONS & NEXT STEPS
All outlet channels have a finite carrying capacity. The Sylvan Creek is functioning as it is intended with no artificial restriction.
The lake levels are naturally high and part of the normal fluctuations between low and high water levels. The wet cool spring coupled with a high spring snowpack (as well as a healthy groundwater inflow) are believed to be the main factors in the high lake levels observed in 2011.
The hydraulic control point of the outlet channel is at the lake outlet. The lake outlet is in a relatively natural state and is relatively stable since at least 1978. The measured sill elevation is 936.7 m which corresponds quite well to previously reported sill elevations in 1978 and 2005 but not well to historic values.
Options are available to manage water levels or the erosion. Focusing on the outlet structure will take additional evaluation to refine the options and evaluate the costs and benefits. Lake focus options such as shoreline protection and, in particular, natural buffers are the favoured options even though they do not control lake levels.
The following action items are to be followed up with by Environment and Sustainable Resource Development staff:
a) Provide this assessment to the Sylvan Lake Management Committee members as part of the communication commitment on Sylvan Lake water levels; b) Complete the water balance for Sylvan Lake to better assess the efficacy of potential improvement options; and c) Work with the Sylvan Lake Management Committee on a preferred option to assess the benefit and efficacy of various water management control scenarios once the water balance has been completed.
Sylvan Lake Water Level Assessment and Options Page 21 of 22 October 2012
BIBLIOGRAPHY
Bioengineering for Stream Bank Erosion Control (1997), Report 1 ‐ Guidelines, Hollis Allen & James Leech, U.S. Army Corps of Engineers, Technical Report EL‐97‐8
Cygnet Lake Final Design Report (1999), Ducks Unlimited, prepared for Cygnet Lake Drainage District
Erosion and Sedimentation Control Manual (2011), Alberta Transportation
Solutions for Shoreline Erosion – A Basic Guide to Bioengineering (2011), Version 1.0, Rideau Valley Conservation Authority
Sylvan Lake Outlet – Model Calibration Report (2012), MPE Engineering Ltd., prepared for Alberta Environment and Water
Sylvan Lake Regulation Study (1978), Planning Division, Alberta Environment
Sylvan Lake Water Quality Assessment and Watershed Management Considerations (2005), AXYS Environmental Consultants Ltd., prepared for Lacombe County et al.
Sylvan Lake‐Cygnet Lake Study (1994), Water Resources Services, Alberta Environment
The Shoreline Stabilization Handbook for Lake Champlain and Other Inland Lakes (no date), Northwest Regional Planning Commission, ISBN 0‐9754546‐0‐9
Sylvan Lake Water Level Assessment and Options Page 22 of 22 October 2012
APPENDIX A ‐ SYLVAN CREEK OWNERSHIP
Sylvan Lake Water Level Assessment and Options October 2012 Below is a rough diagram showing the ownership of the channels along the initial approximately 800 m of Sylvan Creek. The initial 125 m of Sylvan Creek (shown as green) is indicates the crown owned land administered by Public Lands Division of ESRD. Alberta Transportation is responsible for the areas identified in Pink and Alberta Environment and Sustainable Resource Development is responsible for the areas shown in yellow.
APPENDIX B ‐ SYLVAN LAKE ADVISORY COMMITTEE MINISTERIAL ORDER AND RECOMMENDATIONS
Sylvan Lake Water Level Assessment and Options October 2012
APPENDIX C ‐ MPE ENGINEERING LTD. OUTLET CHANNEL ASSESSMENT REPORT
Sylvan Lake Water Level Assessment and Options October 2012 #302, 4702 – 49 Avenue Red Deer, AB T4N 6L5 Phone: 403-348-8340 Fax: 403-348-8331
Alberta Environment and Water January 26, 2012 Central Region File: N:\41\20\006\00\L01-1.0 304, 4920 – 51 Street Red Deer, AB T4N 6K8
Attention: Terry Chamulak, P.Eng.
Dear Mr. Chamulak:
Re: Sylvan Lake Outlet – Model Calibration
In response to your request, MPE Engineering Ltd. has provided a calibrated model of Sylvan Creek at the outlet of Sylvan Lake. A brief description of methodologies and data used in the calibration is provided hereunder.
BACKGROUND In 2011, water levels in Sylvan Lake were the highest since records began in 1918. During 2011, Alberta Environment and Water (AEW) received inquiries about whether the Sylvan Creek channel had any influence on causing the excessive water levels. The location of the hydraulic control point is critical in determining the degree to which the channel has influence on water levels in Sylvan Lake. From observation of flows during 2011, AEW determined that the hydraulic control point for the Sylvan Lake water levels was located in the outlet channel between the lake and the railroad bridge. To determine the exact location, AEW retained MPE to conduct a topographic survey of the channel and produce a hydraulic model using the HEC-RAS (Hydrologic Engineers Corps - River Analysis System) software. The model was to be calibrated using water level data collected by AEW staff in 2011. The model was to be set up so that 2011 outflow conditions could be replicated and scenarios could be developed in the future for planning purposes.
STUDY REACH DESCRIPTION The study reach consists of the upper 1.1 km of the Sylvan Creek channel, extending from the Sylvan Lake outlet located in the southeast corner of the lake in NW 3-39-01-W5, to immediately upstream of the Hwy 11A culvert (about 100 m downstream of the railroad bridge) in SW 3-39-01-W5, as shown in Figure 1.
From Sylvan Lake, the first 100 m of the channel drains eastward towards Hwy 20, and is in a relatively natural state. The channel itself is largely free of vegetation with a sandy silt substrate and varies from 1 to 2 m wide and 0.3 m deep. It meanders through a wetland about 35 m wide, comprised of dense emergent vegetation (Photo #2). Organic matter and sediment tend to accumulate and lodge at the entrance to the outlet, and tend to dampen wave heights (and erosion potential) in the channel. This accumulation may also have some influence on the rate of outflow from the lake.
Once the channel reaches Hwy 20, it veers 90° southward and becomes a straight, uniform road ditch which flows along the west side of the highway for about 770 m, to the railroad embankment (Photos #4- 6). At highest flows, the channel is about 4 m wide and 0.6 m deep, lined with gravel and not vegetated. The channel banks immediately adjacent the active channel are vegetated with unmowed grasses. Towards the Hwy 20 shoulder, the east bank rises another 1.5 m and is vegetated with mowed grasses. The west bank rises another 1 m to 1.5 m and has been left to revegetate naturally. It is currently covered in grasses and woody shrubs. Alberta Environment and Water File: N:\41\20\006\00\L01-1.0 January 26, 2012 Page 2
Figure 1: Location Plan
Study Reach Upper Limit Hwy 20 N culvert
N
Sylvan Lake
Hwy 20 S culvert
Erickson Drive Twin Culverts
Sylvan Creek
Railroad Bridge Study Reach Lower Limit
Hwy 11A
A 1400 mm culvert (Hwy 20 - N culvert) crosses Hwy 20 where the channel enters the road ditch at Hwy 20 (Photo 3). This culvert replaced a bridge at this location, when the natural outlet channel originally crossed the highway. Some gravel has accumulated at both ends of this culvert. The effective invert (i.e. height of gravel) at the west end of this culvert lies 0.1 m above the outlet channel elevation, 0.01 m higher than the effective invert at the east end, and 0.11 m lower than the ditch invert on the east side of Hwy 20.
About 350 m south, the channel crosses Erickson Drive through twin 1200 mm culverts (twin culverts). AEW staff indicated that the west twin culvert was 70% blocked with accumulated gravel and was cleaned out in early summer, 2011 (prior to collecting the calibration data). The bottom 0.3 m of the west culvert was filled with gravel and sediment during the remainder of 2011.
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A second 1400 mm culvert (Hwy 20 S culvert) crosses Hwy 20 immediately south (downstream) of the twin culverts. The west invert of this culvert is at the same elevation as the channel invert, 0.2 m lower than the east invert, and 0.1 m lower than the ditch invert on the east side of Hwy 20.
At the railroad embankment, the channel veers away from Hwy 20 at 45° and southwestward along the railroad embankment for 135 m. The channel dimensions and vegetation are similar to that found along Hwy 20. From there, the channel then turns 90° to the southeast where it immediately flows under the railroad bridge (Photos #7-8). This bridge is a wooden structure with 4 rows of 4 piers. The centre 2 rows have a span of about 2.1 m, about the width of the active channel. The remaining spans vary from 3.1 to 3.4 m. The bridge low chord is about 2 m above the channel invert.
From the railroad bridge, the channel flows southeastward for about 100 m where it then crosses Hwy 11A through a 1400 mm culvert. The active channel is about 2 m wide and 0.6 m deep, and is not vegetated. The overbank areas are heavily vegetated with grasses and brush (Photo #9).
TOPOGRAPHIC SURVEY On December 7-8, 2011, MPE conducted a topographic survey of the 1.1 km study reach of the Sylvan Creek channel, from Sylvan Lake to the railway bridge, with the Altus APS-3 GPS instrumentation system. The horizontal and vertical controls were based on ASCM (Alberta Survey Control Marker) 473652, and tied to ASCM 360784.
Throughout the study reach, the channel was covered with an 8 cm layer of ice and a 10 cm layer of snow, except at the lake where open water existed along a narrow section of channel with greatest Secondary channel velocities. This necessitated the use of an ice auger to obtain ground elevations. Because of the high water levels, outflow from the lake was still occurring (Photo #2).
The channel geometry in the study reach was obtained by surveying cross-sections at roughly 30 m intervals. An average of nine points were surveyed per cross-section, which consisted of 1 to 3 points within the active channel, 2 points for edge of water or ice, and the remaining points defining break lines on the banks, and top of bank or shoulder of road. Other surveyed items of note included random elevations of the wetland and the channel through the wetland, culvert inverts and obverts, and railroad bridge details.
Although the ice and snow cover visually impeded the ability to determine the exact location of the channel bottom, the survey data are expected to provide a reasonably accurate representation of the channel for the intended purposes considering that the channel is relatively consistent in cross-section being that it is a constructed road ditch, and that the distances between surveyed cross-sections are relatively short.
At the time of survey, no flows were observed through the Hwy 20 culverts.
The survey data were then processed using Carlson Civil Suite 2011 on the AutoCAD 2010 platform (.dwg extension), to produce a contour map. From the contour map, cross-sections can be generated for any location along the study reach. For this study, cross-sections were generated at strategic locations and used in the HEC-RAS model.
The produced contour map, complete with surveyed data points and locations of generated cross-sections, is submitted in .dwg format separate from this letter.
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HEC-RAS MODEL As was requested by AEW, the widely accepted HEC-RAS Version 4.1 software was used for this analysis. HEC-RAS is a generalized one dimensional flood routing model for steady and/or unsteady flow simulation. A complete description is available in the HEC-RAS Reference Manual. Data requirements include: • the channel geometry, in the form of cross-sections at strategic locations, must be numbered sequentially from downstream to upstream, • locations and dimensions of structures, such as bridges and culverts, and • energy losses of the channel and floodplain (Manning’s n) and expansion and contraction losses of channels and structures.
A total of 54 cross-sections were generated and used in the model. These were numbered sequentially and correspond to the distance from the culvert inlet at Hwy 11A. In addition, geometric data describing the twin culverts and the railroad bridge were also included. A summary of the data used in the model is presented in Table 1.
Table 1: Channel and Structure Data used in the HEC-RAS Model
Average Distance Length of Cross- Location in Number of Between Channel, sections Study Reach Cross-sections Cross-sections, m ID# m From Sylvan Lake to 125 8 1025 - 1150 16 Hwy 20 N culvert From Hwy 20 N culvert 335 14 690 - 1025 24 to Erickson Drive Erickson Drive twin 1200 mm culverts 40 2 650 - 690 20 (24 m long) From Erickson Drive to 537 22 113 - 650 25 Railroad Bridge Railroad Bridge 6 2 107 - 113 3 15 m span (4 m wide) From Railroad Bridge to 107 7 0 - 107 16 Hwy 11A culvert
Of note, not included in the model were the two culverts which cross Hwy 20 (N culvert and S culvert), and any potential inflows from local runoff along the study reach. This decision was justified considering: • there was no record of observation of water flowing through these culverts, and • any potential flows through these culverts or rate of inflow from local runoff were expected to have insignificant influence on water levels in Sylvan Lake.
The model can be modified to include these components at any time in the future.
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CALIBRATION DATA AND METHODOLOGY After entering the geometric data, the model was calibrated using the limited 2011 data collected by AEW. The collected data comprised of instantaneous water levels taken at the Erickson Drive twin culverts using a tape measure and construction level on four random dates between July 15 and August 14, 2011. The raw data were recorded to a local datum. These elevations were since converted to permanent elevations consistent with the survey by MPE.
Because calibration data were collected at only one location, a vast number of calibration solutions are possible. To aid in the calibration, the collected data were supplemented with the daily average water levels of Sylvan Lake for the days corresponding to those AEW collected the calibration data, estimated from the preliminary data available from Water Survey of Canada, as depicted in Figure 2.
Figure 2: Preliminary Record of Sylvan Lake 2011 Water Levels
A summary of the data used for calibrating the model is presented in Table 2. As can be seen, the range of water levels is very narrow and therefore limited calibration to high flow conditions. Also, as Sylvan Lake water levels rose, the water levels at the Erickson Drive twin culverts tended to drop. This is inconsistent with the expected relationship (i.e. as Sylvan Lake levels rise, water levels at the twin culverts would also rise). As such, consistent calibration results could not be obtained by adopting all the collected data.
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Table 2: Calibration Data
Measured Water Level, m Water Level Location July 15 July 20 August 6 August 14
Sylvan Lake 937.20 937.24 937.27 937.29
Twin Culverts E. Inlet 936.89 936.90 936.88 936.85
Twin Culverts E. Outlet 936.85 936.85 936.84 936.83
Besides the potential inaccuracy of the AEW survey, possible factors which could have influenced the measured data may include: • vegetation growth or decay conditions in the channel could change the roughness of the channel (Manning’s n values), • gradual washout of channel obstructions (debris, sediment) downstream of the twin culverts, and • gradual reduction of deposits within the twin culverts.
Unfortunately, channel conditions during measurement were not recorded, so these possible factors cannot be verified. For calibrating the model then, the data obtained on the last collection date was deemed to be most representative of current conditions.
The procedure used to calibrate the model was as follows: • input estimated Manning’s n values for channel and overbank • assume a discharge rate and run the model • compare model output water levels with measured water levels at the known locations • repeat adjustments to Manning’s n values and assumed discharge rates within a reasonable range of values till model output water levels match measured water levels.
Results of the calibration are discussed in the following section.
MODEL RESULTS AND DISCUSSION A comparison of the calibrated model results and the data measured by AEW is presented in Figure 3. The chart makes obvious the measured data showing an unexpected relationship of declining water levels at the twin culverts with increasing water levels on Sylvan Lake. The chart also shows the results of the calibrated model fitting well with the August 14, 2011 measured data (points on the right side). The model results provide a reasonable relationship between water levels of Sylvan Lake and at the Erickson Drive twin culverts.
The chart also shows that, as discharges increase, the difference in water level elevations between the inlet and outlet of the twin culverts gradually increases. This result is reasonable and expected, considering there would be increasing energy losses (losses due to friction; contraction and expansion losses at the inlet and outlet, respectively) through the culverts as discharge (and velocity) increase.
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Figure 3: Comparison of Model Results with AEW 2011 Measured Data
937.00 936.90 936.80 936.70 936.60 936.50 936.40 1200 mm culvert 936.30 diameter 936.20 Inlet, Measured 936.10 Inlet, calibrated 936.00 Outlet, measured 935.90 Outlet, calibrated
Water Level at Erickson Drive Culvert, metres Culvert, Drive at Erickson Level Water 935.80 937.20 937.22 937.24 937.26 937.28 937.30 Sylvan Lake Water Level, metres
The resulting adopted Manning’s n values are presented in Table 3. These values are within accepted published limits for these conditions, and are consistent throughout the reach.
Table 3: Adopted Manning’s n Values
Manning’s n Value Study Reach Location Channel Length, m Channel Overbank
From Sylvan Lake to Hwy 20 N culvert 125 0.080 0.200 From Hwy 20 N culvert to Erickson 343 0.050 0.100 Drive Erickson Drive 24 0.023 0.100 twin 1200 mm culverts (24 m long) From Erickson Drive to Hwy 11A 658 0.050 0.100 culvert
From the model, the stage-discharge relationships shown in Figure 4 are derived for: • Sylvan Lake at the outlet • Erickson Drive twin culverts inlet, and • Erickson Drive twin culverts outlet.
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Figure 4: Stage – Discharge Relationships for Selected Locations
937.4
937.2
937.0
936.8
936.6
Elevation, metres Elevation, Sylvan Lake Water Level 936.4 Twin Culverts Inlet 936.2 Twin Culverts Outlet
936.0 0.0 0.5 1.0 1.5 Discharge from Sylvan Lake, cubic metres per second
Highlights of the stage-discharge relationships are: • Outflow from Sylvan Lake ceases when the lake elevation is at or below 936.70 m. • As water levels rise in Sylvan Lake, discharge increases. • The difference in water level elevations between Sylvan Lake and the twin culverts lies in a narrow range of 0.38 m to 0.44 m, for the range of discharge between 0.25 m3/s and 1.5 m3/s.
Profiles of the channel thalweg (lowest part of the channel) and water levels for a discharge of 1.25 m3/s (similar to the estimated discharge (from the calibration) of 1.2 m3/s for August 14, 2011) is produced by the HEC-RAS software and presented in Figure 5. For convenience, samples of plotted cross-sections from the HEC-RAS software are presented in Figures 6 and 7. All profiles and cross-sections for this study are available directly from the HEC-RAS model.
CONCLUSIONS The following conclusions are made from the model calibration: • The data collected in 2011 for calibration are not consistent with the expected relationship of increasing flows with increasing water levels, so model calibration was limited to the data recorded on the last date of collection. • The resulting calibration appears to be reasonable. • The location of hydraulic control point appears to be near the Sylvan Lake outlet, at the point of the highest thalweg elevation. • Confidence in the model calibration results could be improved with more measured data (water levels and discharge) for various water levels of Sylvan Lake. • Accurate representation of historic outflow discharge rates and water levels may not be achievable due to possible changes in channel conditions, such as:
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Figure 5: Profiles of the Study Reach
Sylvan Lake Outlet Plan: Plan 03 25/01/2012 Sylvan Creek Outlet 938.5 Legend
Railroad Erickson Drive EG 1.25 m3/s 938.0 Bridge Twin Culverts WS 1.25 m3/s 937.5 Crit 1.25 m3/s
Ground 937.0
936.5 Elevation (m)Elevation
936.0
935.5
935.0 0 200 400 600 800 1000 1200 Main Channel Distance (m)
Figure 6: Cross-section of Erickson Drive Twin Culverts
Sylvan Lake Outlet Plan: Plan 03 25/01/2012
.1 .05 .1 938.5 Legend
938.0 EG 1.25 m3/s WS 1.25 m3/s 937.5 Crit 1.25 m3/s
937.0 Ground Bank Sta Elevation (m)Elevation 936.5
936.0
935.5 6 8 10 12 14 16 18 20 22 24 Station (m)
Figure 7: Cross-section of Railroad Bridge
Sylvan Lake Outlet Plan: Plan 03 25/01/2012 RR bridge .1 .05 .1 938.5 Legend
938.0 EG 1.25 m3/s WS 1.25 m3/s 937.5 Crit 1.25 m3/s
937.0 Ground Bank Sta Elevation (m)Elevation 936.5
936.0
935.5 0 2 4 6 8 10 12 14 16 18 Station (m)
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Sylvan Creek Photographs, taken December 7-8, 2011.
#1: Looking E at Sylvan Lake Outlet. #2: Looking SE at wetland and channel.
#3: Looking E at channel to Hwy 20. #4: Looking S at channel along Hwy 20.
#5: Looking N at channel from Erickson Drive. #6: Looking NE at channel along railroad embankment.
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#7: Looking SE towards railroad bridge. #8: Looking SE at railroad bridge detail.
#9: Looking SE from railroad bridge towards Hwy 11A.
APPENDIX D ‐ HEC‐RAS MODEL RESULTS
Sylvan Lake Water Level Assessment and Options October 2012 MEMO 2 SILVAN LAKE OUTLET CAPACITY
This Memo contains additional Scenario simulations for the Sylvan Lake outlet capacity study, following the presentation on and discussions on June 14th. This Memo contains the following sections:
1. Previous Simulated Scenarios 2. Future works 3. Changes of Rating Curves with Time 4. Influence of the 90O Bend 5. Trend in the Sylvan Lake Reported Water Surface Elevations
1. PREVIOUS SIMULATED SCENARIOS
The results of several simulations indicated that changes on the rating curve at the Sylvan Lake Outlet were small when changes at the constructed channel (including culvert clean up, obstruction removals, culvert removals, reshape and cleaning of the natural channel) were imposed.
2. FUTURE WORKS
Figure 1 presents the results for four different scenarios:
Current calibration The natural channel has been cleaned to the constructed channel current conditions. The constructed channel is extremely clean. This scenario assumed that the natural channel preserved the current calibration values for n. The natural channel is extremely clean. This scenario assumed that the constructed channel preserved the current calibration values for n.
Figure 1 indicates that for the same discharge, the Sylvan Lake outlet water surface elevation is less if the natural channel is kept extremely clean than if the constructed channel is kept super clean, this for discharges up to 0.90 m3/s
A discharge of 0.90 m3/s corresponds to a lake elevation of 937.15 m which have been reported to be exceeded only 2% of the time for the last 30 years. Therefore, cleaning efforts should be placed on the natural channel section of the Sylvan Lake outlet channel.
937.4
937.3
937.2
937.1
937.0 Current Calibration (Scenario 1)
Natural channel cleaned to 936.9 constructed channel conditions n = 0.03 Down of 1000m 936.8 n = 0.03 Up of 1000 m Sylvan Lake Water Elevation (m) 936.7 0.20.30.40.50.60.70.80.91.01.11.2 Discharge (m3/s)
Figure 1. Future Works
3. CHANGES IN RATING CURVES WITH TIME
Figure 2 indicates that prior to 1988, discharges up to 0.4 m3/s (15 cfs) required less energy (Water surface elevation at the lake) to be discharged than the 91-92 case. By comparing Figure 1 and Figure 2 it can be inferred that the discharge at the current outlet channel can be improved to pre 1988 conditions if the natural section of the Sylvan Lake outlet channel is cleaned up.
For discharges larger than 0.4 m3/s (15 cfs), Figure 2 indicates that the current outlet channel is more efficient than the pre 1988 channel.
Figure 2. Sylvan Lake Outflow Rating Curves
4. INFLUENCE OF THE 90O BEND
The 90O bend was simulated in the HEC RAS model by including a large local loss coefficient, K = 0.95. When this coefficient is multiplied by the downstream velocity head (V2/2g) produces the total energy los generated by the 90O bend.
Simulations results indicated that the downstream velocities were around 0.60 m/s for discharges smaller than 1.2 m3/s. Therefore, the expected maximum energy head loss is close to 0.602/(2*9.81) = 0.018 m.
HEC RAS adds this head loss to the estimated normal flow at Station 1000 m and continues to compute the water surface profile in the upstream direction since the flow is subcritical for all the discharges.
This backwater effect had a small effect on the Sylvan Lake outlet rating curve as indicated in Figure 3 where Scenario 1 is compared with the case where the 90O bend was treated as a typical contract/expansion local feature.
937.4
937.3
937.2
937.1
937.0 Current Calibration (Scenario 1) No 90D Bend
936.9
936.8 Sylvan Lake Water Elevation (m) 936.7 0.20.30.40.50.60.70.80.91.01.11.21.31.41.5 Discharge (m3/s)
Figure 3. Comparison Scenaro1 and Scenario 12 (No 90O bend)
5. TREND IN THE SYLVAN LAKE REPORTED WATER SURFACE ELEVATIONS
Figure 3 indicates that there is a trend in the water surface elevation (WSE) at the Sylvan Lake. This trend may be explained by the increment in the annual precipitation amounts as indicated in the SLMC-TAT report. 937.2 937.1 937.0 936.9 936.8 936.7 (m) 936.6
WSE 936.5 936.4 936.3 936.2 936.1 936.0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year
Figure 3. Sylvan Lake WSE Trend
6. CONCLUSIONS
The Sylvan Lake outlet channel needs to be maintained and cleaned up in order to have similar conveyance capacities to pre 1988 conditions. These works are required since there is an increasing trend in the reported Sylvan Lake water surface elevations (probably due to increasing rainfall amounts) combined with a smaller outlet capacity of the current channel (for discharges smaller than 0.4 m3/s or 15 cfs).
Cleaning efforts should be focused on the natural channel (see Figure 2) since having this channel cleaned would provide enough discharge capacity for the most frequent events.
SCENARIOS
08/91-12/92 Rating Curve
Comparison indicates that outlet conditions are similar since 1991.
Cleaned Natural Channel
This scenario assumes that the natural channel has the same Manning’s n as the constructed channel i.e. n = 0.05 and 0.1 for the channel and bank areas, respectively.
Dragged Clean Natural Channel
This scenario includes some excavation in the natural channel up to a width of 2 m.
Reshaped Inlet
Same Scenario as before.
ANALYSIS
Outlet capacity has been kept similar since 1991. Best capacity improvement was obtained either by performing some excavation on the natural channel or by Re-shaping the inlet. Improvement between 10 and 3 cm.
937.3
937.2
937.1
937.0
936.9 Current Calibration (Scenario 1)
08/91-12/92
Sylvan Lake Water Lake Sylvan Water Elevation (m) 936.8 Cleaned Natural Channel
Excavated Clean Natural 936.7 Channel Reshaped Inlet
936.6 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Discharge (m3/s)
APPENDIX E ‐ SYLVAN LAKE AIR PHOTOS
Sylvan Lake Water Level Assessment and Options October 2012
Figure 1 ‐ Sylvan Lake Outlet June 15, 1990. Water levels were 936.76 m. Visible channel exists although no clear indication of channel flow.
Figure 2 ‐ Sylvan Lake Outlet October 2, 1991. Water levels were estimated in the range of 936.93 m to 936.95 m. Clear indication of channel flow is visible.
Figure 3 ‐ Sylvan Lake Outlet June 19, 1992. Water levels were 937.09 m. Lake outlet appears overgrown with partially visible channel and indication of channel flow.
Figure 4 ‐ Sylvan Lake Outlet July 12, 1993. Water levels were 937.12 m. Considerable fill is observed on north side of Sylvan Creek. Open water is visible in shoreline marsh with flow in channel.
Figure 5 ‐ Looking west to Sylvan Lake at existing outlet channel. Landfill encroachment shown to the north (right side of photo) of Sylvan Creek. Lake elevation was 936.9 m. No date. Source: Sylvan Lake‐Cygnet Lake Study (1994).
Figure 6 ‐ Looking east from Sylvan Lake at existing outlet channel December 7‐8, 2012. Lake elevation is unknown. Source: Sylvan Lake Outlet – Model Calibration Report (2012).
Figure 7 ‐ Sylvan Lake Outlet Channel Reach from Sylvan Lake to Highway 11A (1949 to 2007) Figure 8 ‐ Sylvan Lake Outlet Channel ‐ 2007 (channel length 1075 m estimated from Highway 20 to Highway 11A)
Figure 9 ‐ Sylvan Lake Outlet Channel – 1969 (channel length 1142 m estimated from Highway 20 to Highway 11A)
Figure 10 ‐ Sylvan Lake Outlet Channel – 1966 (channel length 1162 m estimated from Highway 20 to Highway 11A)
Figure 11 ‐ Sylvan Lake Outlet Channel – 1949 (channel length 1176 m estimated from Highway 20 to Highway 11A)
Page E8 of 8
APPENDIX F ‐ OPTIONS MATRIX
Sylvan Lake Water Level Assessment and Options October 2012 Sylvan Lake Options Matrix
Option Key Elements Pros Cons Upgrade outlet channel Re‐grade outlet to an elevation of Outlet upgraded and lake levels lowered; Maintenance of outlet channel required on a 936.5 m (about 0.2 m lower); No impediment to fish movement; regular basis; Improved channel downstream for Pike spawning habitat potential is maintained; Lake levels will still fluctuate naturally; initial 125 m only by straightening and No operation on lake levels necessary; Perception of mismanagement of water levels clearing channel; Average water levels will correspondingly will likely continue (i.e. low water levels); No significant improvements to decrease once the lake levels re‐stabilize Increased flows to Cygnet Lake may exacerbate downstream infrastructure (unless around the new sill elevation; flooding issues requiring extensive consultation; more detailed analysis indicates Extent of downstream channel upgrades will further upgrades are necessary); need to be assessed (further upgrades may Flow continues along west side of increase cost); Highway 20; (very) Conceptual cost is approximately $100,000; Greater water management complexity at Cygnet Lake and at Sylvan Lake; Control Structure Install control structure; Control mechanism for Sylvan Lake outlet; Operation and maintenance plan is required Upgrade channel downstream; Range of lake level fluctuations is reduced; and necessitate agreement with a number of Upgrade downstream infrastructure Enhanced shoreline stability; stakeholders; (i.e. crossings, culverts); Fish egress is reduced; Public perception of a control structure may Involves Restoration of Sylvan Creek in lead to greater expectations of greater control pre‐1988 channel; of high/low water levels; Increased flows to Cygnet Lake may exacerbate flooding issues requiring extensive consultation; Extent of downstream channel upgrades will need to be assessed (further upgrades may increase cost) (very) Conceptual costs is approximately $1,700,000; Greater water management complexity at Cygnet Lake and at Sylvan Lake; Maintain outlet Straighten and clear existing channel; Channel capacity will be maintained; Unlikely to have a significant impact on the lake Debris (woody & plant material) Relatively easy to accomplish, no specialist or levels; removal by hand; engineering required; As with previous channel options above, Sill elevation not altered; No capital investment required, periodic debris procurement of regulatory approvals are Outlet capacity is not significantly removal upon inspection; required; altered; Erosion protection Lake continues to fluctuate naturally; Protection for toe and upper bank erosion; No change in natural lake level fluctuations; Shoreline armored with rip‐rap; Good protection right after installation (no Placement of rock limited to ice covered Sylvan Lake Options Matrix
Option Key Elements Pros Cons The armored shoreline requires to establishment period); conditions; have viable vegetation established Good healing during rock displacement or Significant costs to the lot owner ranging from which will enhance shoreline stability movement; about $10,000 to $15,000 for a 20 m wide lot and provide for fish habitat; Relatively easy to install and repair; (very conceptual cost basis); No fish habitat compensation is needed (at this Ice can displace rock requiring regular time) if viable vegetation is established; maintenance; Shoreline armoring can be done without the Armored shorelines may be less visually need of professional engineer; appealing and more difficult to access from Normally requires the establishment of shore; vegetation as part of the approvals; Extreme high lake levels may continue erosion if armoring does not extend high enough; Retaining walls Lake continues to fluctuate naturally; Protection for toe and upper bank erosion; No change in natural lake level fluctuations Use of sheet steel, concrete or large Good protection right after installation (no Considerably more construction involved & armor stone can be used to produce a establishment period); engineering; vertical flat‐faced wall; Can fit into enhanced yard landscaping; Higher maintenance costs than rock armoring; Toe armoring recommended to Rock stabilization may need to be placed at toe prevent undermining of retaining wall; to prevent undermining; Vertical walls tend to deflect energy rather than dissipating it, potentially resulting in erosion problems elsewhere; Fish compensation necessary as there is a loss of habitat; Bioengineering (soft Lake continues to fluctuate naturally; Grows stronger with age; No change in natural lake fluctuations; structures) Bioengineering incorporates plants in Relatively low cost; May be considerable establishment time before combination with natural materials Natural appearance; vegetation is effective (high failure rate initially (logs, stakes, brush bundles); and potential for repeat seeding); Natural buffer The lake fluctuates naturally and allow Low costs and labour; No change in natural lake fluctuations; buffers to erode; Aesthetically pleasing; Vegetated banks may be unsightly as they Natural vegetation of buffers is No impediment to fish movement and pike recede and fall in; encouraged; spawning habitat is maintained; May be considerable establishment time before This involves maintaining a buffer Natural vegetated banks heal and repair vegetation is effective (high failure rate initially distance between the lake and naturally; and potentialr fo repeat seeding); subdivisions and limiting development Does not provide an answer to existing on MRs and ERs; developed lots or subdivisions; Concerns with high water levels will likely persist as erosion and damage continues;
APPENDIX G ‐ CONCEPTUAL COST ESTIMATES BASIS FOR OPTIONS
Sylvan Lake Water Level Assessment and Options October 2012 Upgrade Sylvan Creek Option
Cost Estimate
Item Description Quantity Unit Unit Cost Cost (#) (#) ($/unit) ($ 2012)
1 Mobilization and Demobilization 1 LS 5,000 5,000
2 Care of Water 1 LS 20,000 20,000
3 Common Excavation & Material 1 LS 10,000 10,000 Disposal
4 Pre‐ and Post Construction Surveys 1 LS 5,000 5,000
5 Regulatory Approvals Procurements 1 LS 25,000 25,000
Subtotal: 65,000 Contingency @ 25% Subtotal: 16,250 Engineering @ 15% Subtotal: 9,750 Total: $91,000 ROUNDED TOTAL: $100,000
Annual O&M costs estimated at 0.8% capital ($100,000) costs = $800
Outlet Control Structure on Sylvan Creek Option
Cost Estimate
Item Description Quantity Unit Unit Cost Cost Cost (#) (#) ($/unit) ($ 1994) ($ 2012) 1 Mobilization and Demobilization 1 LS 30,000 30,000 46,104
2 Care of Water 1 LS 15,000 15,000 23,052
3 Common Excavation 1 LS 100,000 100,000 153,680
4 Sylvan Lake Control Structure 1 LS 95,000 95,000 145,996
5 Culvert Crossings 1 LS 260,000 260,000 399,586
6 CN Bridge Protection 1 LS 10,000 10,000 15,368
7 Landscape Reclamation 1 LS 60,000 60,000 92,208
8 Fencing 1 LS 30,000 30,000 46,104
9 Utility Crossings 1 LS 30,000 30,000 46,104
10 Pre‐ and Post Surveys 1 LS 5,000 5,000
11 Regulatory Approvals Procurements 1 LS 250,000 250,000 & Consultation Subtotal: 1,223,202 Contingency @ 25% Subtotal: 305,801 Engineering @ 15% Subtotal: 183,480 Total: $1,712,483 ROUNDED TOTAL: $1,700,000
Annual O&M costs estimated at 0.8% capital ($1,700,000) costs = $13,600
Note: this option is primarily based on “Alternative B” as identified in the Sylvan Lake‐Cygnet Lake Study (1994) and adjusted for work scope and adjusted to 2012 CDN dollars (Alberta CPI from 1994 to June 2012 is 1.5368) Maintain Sylvan Creek Option
Cost Estimate
Item Description Quantity Unit Unit Cost Cost (#) (#) ($/unit) ($ 2012)
1 Mobilization and Demobilization 1 LS 5,000 5,000
2 Care of Water 1 LS 10,000 10,000
3 Common Excavation & Material 1 LS 5,000 5,000 Disposal
4 Regulatory Approvals Procurements 1 LS 20,000 20,000
Subtotal: 40,000 Contingency @ 25% Subtotal: 10,000 Engineering @ 15% Subtotal: 6,000 Total: $56,000 ROUNDED TOTAL: $50,000
Annual O&M costs estimated at 0.8% capital ($50,000) costs = $400
Shoreline Erosion Protection (Rip Rap Shoreline)
Cost Estimate (per m length of yard frontage)
Item Description Quantity Unit Unit Cost Cost (#) (#) ($/unit) ($ 2012)
1 Excavation (Unit Price Item G225) 1.4 m3 5.00 7
2 Geotextile (Unit Price Item E456) 2.0 m2 2.00 4
3 Rip‐Rap Bedding 0.4 m3 75 30
4 Rip‐Rap, random supply and place 1.0 m3 250 250 (Unit Price Item F500)
Subtotal 1: 291 Construction & Mobilization @ 100% of Subtotal 1: 291 Subtotal 2: 582 Contingency @10% of Subtotal 2: 58 TOTAL: $640
* Cost of rip‐rap armoring for shoreline erosion control is estimated to be $640/m lot width. The rounded total cost for a 20 m wide lot would be in the range of $10,000 to $15,000.
** Unit prices from Unit Prices Averages Reports produced by Alberta Transportation for 2012.
APPENDIX H ‐ PRESENTATION SLIDES & SPEAKING NOTES
Sylvan Lake Water Level Assessment and Options October 2012 PRESENTATION SLIDE NOTES
Several presentations were delivered between April 2012 and July 2012 on the assessment as information became available and concerns over lake levels continued. Various presentations were delivered to the following:
Sylvan Lake Advisory Committee, April 5, 2012 Town of Sylvan Lake, April 10, 2012 Lacombe County, April 12, 2012 Summer Village of Norglenwold AGM, June 9, 2012 Summer Villages, July 10, 2012
The assessment has evolved somewhat over the time period of the presentations due to additional information becoming available, additional analysis, as well as incorporating comments and questions received during and between presentations.
Two key areas where the assessment has further developed over the period of the presentations are:
1) The historic stage‐discharge curve (is the outlet channel operating as it should?):
During the presentations to the Town of Sylvan Lake and Lacombe County, it was reported that the lake outlet is operating naturally. Since those presentations, previous stage‐discharge curves were reviewed from Sylvan Lake‐Cygnet Lake Study (1994). The curve, constructed from data previous to the study, is slightly different than the one produced from 1991/92 data and the one produced from the 2012 work. It is assumed that the older stage‐discharge curve most closely match what can be considered historically natural. Although the stage‐discharge curve appears to have changed over time, it does not imply that the change is a result of anthropogenic activities. Notes for slide 12 below provide greater description of the key points covered during the presentation.
2) The historic sill elevation (has the sill elevation changed?):
Since 1978, the sill elevation appears to be stable. However, the information located in the Sylvan Lake‐Cygnet Lake Study (1994) suggests that the sill elevation was likely roughly about 0.2 m lower in the 1920s. The presentations to the Town of Sylvan Lake and Lacombe County reported no changes to the sill elevation had occurred. This is accurate since at least 1978 there has not been any significant change; however, it appears to have increased since before this time. Notes for slide 10 below provide greater description of the key points covered during the presentation.
Page H1 of 12 The following slide notes provide the context to the attached slide deck presentation delivered to the Summer Villages on July 10, 2012. Discussion points were generally based on the notes below but not in verbatim. As during any presentation, some points may have been missed and others emphasized but not as well developed in the notes.
Slide 01: Cover Slide
This is the cover slide for the presentation. Alberta Environment and Sustainable Resource Development would like to thank the Summer Villages for the invitation and opportunity to discuss the water levels at Sylvan Lake and the assessment being undertaken. The focus of the presentation covers three areas:
‐ the outlet channel assessment; ‐ key questions and answers; and ‐ water management options.
Slide 02: Outlet Channel Assessment
In 2011 the lake reached its highest recorded average daily water level of 937.3 m (937.308 m to be exact) on August 11th surpassing the previous recorded high of 937.25 m measured in July 1955. Checking the current water level, it is range of 937.16 m to 937.17 m which is close to the values observed at this same time last year.
Over the years, channel realignment projects were undertaken in partnership with the Town of Sylvan Lake, Cygnet Lake Drainage District and Alberta Transportation. These projects were never intended to control the levels of Sylvan Lake but were designed to accommodate development, the wastewater lagoons, and road construction, and manage water in the Cygnet Lake Drainage District (i.e. to ensure the channel doesn’t cause any problems when it is routed around the particular development). The Sylvan Lake Advisory Committee was struck in 1992 to identify options to manage the water. Phase I dealt with Cygnet Lake drainage whereas Phase II would deal with resolving Sylvan Lake water management.
Concerns have been expressed recently on whether the outlet channel was functioning properly or whether it is responsible for causing the high water levels. Alberta Environment and Sustainable Resource Development periodically inspected the channel during the spring and summer of 2011. It was observed that there was high water levels downstream from the twin 1200 mm culverts and during spring of 2011, one of the twin culverts was 80 percent blocked.
Upon request of the municipalities, we had taken a more thorough look at the outlet channel (as well as brought the condition of the culvert to the attention of Alberta Transportation).
Page H2 of 12 Slide 03: Outlet Assessment Survey Reach
Alberta Environment and Water contracted MPE Engineering to assess the outlet channel. The objectives of the contract were to survey the channel, help identify the location of hydraulic control point, and to set up a channel flow model. The hydraulic control point is the most restricted portion of the outlet channel. The location of the hydraulic control point is critical in evaluating the channel and its significance in causing the high lake levels.
The study reach consists of the initial 1.1 km of Sylvan Creek from the lake outlet to the Highway 11A culvert (just downm fro the railway bridge and just upstream of the traffic circle). It wasn’t deemed necessary to survey the channel beyond this location since our previous observations in 2011 showed that the hydraulic control point was upstream of the railway bridge.
The lake outlet itself is in a somewhat or “relatively” natural state for the initial 125 m until it takes a 90o bend at Highway 20 when it follows a constructed channel for another 15 km. Prior to its realignment, Sylvan Creek was an intermittent meandering creek. Currently, there are twin 1200 mm culverts at the Erickson Drive approach and the train bridge crossing.
Slide 04: Channel Profile (flow at 0.25 m3/s)
The channel profiles were surveyed and entered into a HEC‐RAS computer model in order to further assess the channel under different conditions.
The channel floor, shown by the bottom profile between the lake outlet (at the right) to the Highway 11A culvert (at the left), has a maximum elevation of 936.7 m at the outlet of the lake. This corresponds well with the reported elevation of 937.74 m in a 1978 Alberta Environment report and the estimated 936.66 m in the 2005 AXYS report.
The slope is very gradual with a 1.3 m drop in the 1.1 km reach representing a 0.1 percent slope. A rise occurs at approximately 800 m downstream showing some obstruction of flow as illustrated by the deepening and flattening of the water profile up to the culvert. For lake elevations shown here at 936.94 m (about where it peaked in 1999) the water will be flowing at 0.25 m3/s with a water depth of about 0.24 m.
Slide 05: Channel Profile (flow at 0.50 m3/s)
This series of water profiles (shown in the following slides for flowrates 0.5 to 1.25 m3/s) illustrates what happens in the outlet channel as the lake level rises. As the lake levels increase, the water levels and flowrates in the channel correspondingly increase.
Page H3 of 12 Slide 06: Channel Profile (flow at 0.75 m3/s)
Slide 07: Channel Profile (flow at 1.00 m3/s)
Slide 08: Channel Profile (flow at 1.25 m3/s)
This profile is close to the maximum recorded daily average water elevation measured on August 11th last year (this one is about one‐half inch higher). The maximum daily average recorded water depth is 0.61 m above the sill elevation of 936.7 m resulting in a flow of 1.23 m3/s. At this flowrate, the lake would drop about an inch every 10 days just from the outlet channel alone (if there were no other inputs or outputs into or from the lake). The number of days increases substantially as the lake levels drop because the flowrate in the outlet channel will decrease as the lake levels drop.
It was previously noted that one of the twin culverts was 80 percent obstructed (which was subsequently cleaned out by Alberta Transportation in June 2011). Our calculations show that the culverts, even when the one was 80 percent blocked, did not have any negative impact on the channel’s overall carrying capacity or lake levels. We also assessed whether the channel capacity would improve if these culverts were removed and replaced with an open channel. While the channel capacity improves in the immediate vicinity of the removed culverts, it would have no effect on lake levels… because the established hydraulic control point is at the lake outlet.
We had also assessed the benefit in other channel improvements. For some of the calculated scenarios, the assessment focused on the channel from the point where it enters the road ditch along highway 20. Our calculations show that neither smoothing of the channel nor removal of the obstruction (the rise at about 800 m) have any benefit in improving channel flow capacity. It improves in the immediate areas of improvements; however, they do not have any negative effect on the lake levels. Again, this is because the hydraulic control point is at the lake outlet. In other words, significant improvements downstream will not increase the channel’s overall carrying capacity because the channel limit is at the lake outlet.
The measured sill elevation is 936.7 m. This corresponds quite well to the previously reported sill elevation. Although the outlet was not identified to be silted in or blocked, the MPE report indicated that organic matter and sediment tend to accumulate and lodge at the entrance to the outlet. Anytime when the lake outlet is blocked, the outflow rate may be negatively impacted.
Page H4 of 12 We are confident that the control point is at the lake outlet. This is based on the assessment that downstream modifications, such as the culvert itself, removing the blockage, and smoothing the channel downstream of the outlet do not have any effect on overall channel capacity. Only improvements within the initial 125 m of the outlet channel have an improvement on overall channel capacity.
We are also comfortable that the outlet channel is performing as it is intended. It is recognized that the channel has undergone significant modifications over the years including infilling of the shoreline wetland around the lake outlet and routing the creek on the west side of highway 20 (just to name a couple). The channel routing itself would not likely have decreased capacity in the ditch – more likely the opposite. The original meandering channel was a longer less defined channel than the constructed and maintained channel currently on the west side of Highway 20. The previous infilling of the wetlands around the lake outlet itself is not expected to have a significant impact on the channel capacity. Most of the outlet capacity over the defined channel and is not restricted (even with the infilling).
The bottom line is that the channel is believed to be functioning as a natural outlet. It does have a limited carrying capacity (as all channels would) but it did not artificially cause the high water levels in the lake.
Slide 09: Questions and Answers
I would now like to shift the presentation to key questions related to the high lake levels. These will be discussed in the subsequent slides…I encourage additional questions that may be on your mind and will try and answer those as best as possible.
Slide 10: Is the Outlet Silted or Filled In?
The outlet channel is in a “relatively” natural state. The picture in the upper left was taken in December 2011 looking east towards highway 20 and the picture on the lower right was taken in June 1994 looking west towards the lake. The surveyed elevation in 2012 (936.7 m) matched closely with the reported elevation in 1978 (936.74 m) and again with the estimated elevation in 2005 AXYS report (936.66 m). Considering the accuracy expected in locating any natural sill, these values are considered to agree closely.
I understand that debris and vegetation can accumulate at the lake outlet. We visually checked the outlet channel and did not observe any specific issues in 2011 (with the notable exception of the blockage in one of the culverts).
The picture on the lower right shows some infilling of the wetland on the north side of the lake outlet. The Province currently owns a 30 m wide right‐of‐way. Our
Page H5 of 12 evaluation indicates that infilling outside of the right‐of‐way did not significantly impact the lake outlet carrying capacity.
Slide 11: Is it the Outlet Channel?
I think it is widely agreed that lake levels generally rise during cool wet weather and drop when the weather turns hot, dry and windy. The question among many people is whether the outlet structure is operating as it should or have there been changes that cause the lake levels to artificially rise.
This assessment was done with a view of evaluating whether the outlet channel is responsible for the increased lake levels.
What we looked at were:
- Identifying the location of the hydraulic control point; - Comparing the sill elevation to previous years; - Comparing stage‐discharge curves; - Visual condition of the outlet (qualitatively comparing a modified channel with a constructed channel); and - Historic water level record.
Even though the outlet channel has limited carrying capacity, this is not because it has been altered or artificially restricted ‐ there is only so much that can flow through the natural outlet.
Slide 12: Stage‐Discharge Curves
The stage‐discharge curve shows the relationship between the lake elevation and the overall channel conveyance capacity. As the lake level rises, the amount of water flowing in the channel correspondingly increases.
The black line shows the stage‐discharge curve based on the 2012 survey and the blue line shows the stage‐discharge curve based on the 1991/92 data. The tan lines are the stage‐discharge curve envelope and are constructed using historic data from the 1920s and 1955.
What do these curves suggest?
• It is apparent that there is a shift in the stage‐discharge curves over time. The 2012 and the 1991/92 curves compare closely suggesting that the outlet channel is somewhat stable since 1992 and maintaining its flow capacity. The difference is the historic pre‐1988 stage‐discharge curve. • For lower lake elevations, the channel capacity was historically higher but for higher lake elevations (i.e. greater than roughly 937.05 m) the channel
Page H6 of 12 capacity is higher now than historic values. For the current high lake levels, the channel is performing better now than it otherwise would have been using the pre‐1988 stage‐discharge curve. Once the lake drops below roughly about 937.05 m, the current channel will begin to have worse channel flow ycapacit than the pre‐1988 stage‐discharge curve shows. • The historic (pre‐1988) stage‐discharge curve suggests the sill elevation was lower by about 0.2 m. • One potential explanation could be that the pre‐1988 “channel” was wider, potentially lower but also less defined. At lower lake elevations, more flow could be observed but the roughness (possibly due to dense weed growth and more variable natural terrain) and lack of channel definition would allow low levels of flow at lake elevations between 936.5 and 936.7 whereas the current sill elevation restricts outflow until lake levels reaches 936.7 m. Once this occurs, the better defined channel will convey the water at higher rates compared to the previous situation.
Slide 13: Sylvan Lake Levels
The historic levels in Sylvan Lake were looked at and there is an apparent increasing trend since about the mid 1960s. This is worthy of note but does not, in itself, demonstrate that the current high water levels are a result of anthropogenic activity.
Slide 14: Is it the Road?
Highway 20 underwent construction in 1988. One significant change was the replacement of the bridge crossing Sylvan Creek with a culvert. Unfortunately, the culvert was installed inverted (i.e. sloping towards Sylvan Lake) resulting in the channel being routed in its current path along the west side of Highway 20.
Inverted Culvert: the constructed portion of the outlet channel (from the inverted culvert onwards) is expected to provide better flow characteristics than the original meandering Sylvan Creek. The current constructed channel is uniform, straight, smoother, and has slightly higher slope than the original Sylvan Creek would have had.
90o Bend: the outlet channel takes a 90o bend at the inverted culvert. Some dissipation of energy occurs at junctions (including 90o bends) and is proportional to the square of the velocity. Because the velocity is relatively low in the outlet channel, it is not expected that the 90o bend is having a significant effect on lake water levels.
Twin Culverts: the twin culverts under Erickson Drive were evaluated and determined not to have any relevance in backing up water in the lake. The
Page H7 of 12 culverts may become a limiting factor at higher channel flowrates or if channel improvements occur in the initial 125 m.
Rise at 800 m: the ground rise at 800 m was evaluated and determined not to have relevance in backing up the water. Removal of the rise (or the twin culverts) will improve the channel conveyance capacity in the immediate vicinity of the improvement but it will not have any bearing in the overall channel capacity (i.e. the hydraulic control point is within the initial 125 m of the channel).
Train Bridge: Sylvan Creek crosses the train bridge about 1 km downstream of the lake outlet. The creek takes a 90o bend under the crossing. As indicated previously (slide 2), department staff observed that the water was flowing freely under the train bridge and this was not considered to be the location of the hydraulic control point. As such, the train bridge is not felt to be relevant in restricting the overall channel flow capacity.
Slide 15: Is Cygnet Lake Backing Up the Water?
Cygnet Lake is controlled lake with a full supply level of 931.65 m. This is about 5 m lower and several kilometers down gradient from the Sylvan Lake outlet. Our observations of the outlet channel during the spring and summer of 2011 showed that the hydraulic control point was upstream of the railway crossing. Any points downstream of this do not have any influence in backing up the water to the lake outlet.
As indicated before, the assessment identifies the lake outlet is the hydraulic control point. The Cygnet Lake structure is too far downstream to have had any impact on Sylvan Lake.
Flooding would be observed in the local area of the channel flow constriction long before it would back up to Sylvan Lake. This is expected for Cygnet Lake and other points upstream.
Slide 16: Why Not Control the Lake Water Elevation?
Why not control the lake elevation? This question probably relates to the majority of the inquiries. As indicated before, the previous channel modifications were done to accommodate development and were not intended to change the flow characteristics from the lake. It is also recognized that the outlet channel has finite capacity.
With the information we now have, it isn’t a question of “what went wrong with the outlet” (that is to say, is it blocked, is it silted in, etc.) but rather focus on whether there is any benefit to modifying the outlet channel. Channel improvements would
Page H8 of 12 be intended to improve the outlet flow characteristics and have a long term benefit in overall water levels in Sylvan Lake.
At the request of the municipalities, a series of options were evaluated at a (very) conceptual level and these should help with the two questions:
- Why not control the lake water elevation? - What can be done?
Slide 17: What Can Be Done? (Options)
Water management options considered are those listed here. It is recognized that other potential options exist and it is necessary that additional work is needed to further assess the feasibility of these options.
A current water balance model will provide a better understanding of what is happening. The AXYS study in 2005 indicated that about 10 percent of the loss from the lake is through the outlet channel with the majority (about 90 percent) lost through evaporation. {Aside: during the presentation the audience corrected that it is about 95 percent of the water is lost through evaporation}
Removing inputs from the lake or diverting water away from the lake (other than the outlet channel) were not considered feasible as they have potentially significant cost and long term negative impacts to the lake. As such, the options focus on the outlet channel itself and the lake.
Slide 18: Control Structure
A water management option previously identified in the Sylvan Lake‐Cygnet Lake Study (1994) is to construct a control structure. The control structure will have the ability to increase the outflow from Sylvan Lake when the lake is high and install stop‐logs when the flow returns to the normal ranges. The channel will likely need upgrading downstream control structure to ensure the overall capacity is enhanced. Upgrades include culverts and other crossings.
One of the benefits of an outlet structure is that it would provide a control mechanism for lake levels. Although this option was not fully evaluated (i.e. the water balance model is not yet complete), the range of high and low water levels is expected to be reduced and shoreline stability enhanced.
It is also expected that a complex operation plan would be required with the cooperation and agreement of stakeholders both around Sylvan Lake but also downstream. Our experience shows that with control structures, there is a greater perception and expectation that the structure will fully control water levels – in contradiction to the reality where the lakes will still fluctuate but not to the same extent. The increased volume sent to Cygnet Lake must also be assessed as well as
Page H9 of 12 any additional upgrades further down. The (very) conceptual cost estimate is approximately $1,500,000 but it may increase significantly depending on the extent of work needed downstream. {Aside: it was pointed out by the audience that the cost of procuring environmental regulatory approvals also needs to be included in the costs}
This option is based on the Sylvan Lake‐Cygnet Lake Study (1994) and adjusted using the Alberta Consumer Price Index to adjust the costs from 1994 dollars to 2012 dollars.
Slide 18: Upgrade Outlet Channel
This involves the re‐grading of the outlet channel from the lake to highway 20, for about 125 m distance. This option includes lowering of the lake outlet to a final sill elevation of 936.5 m (or a 0.2 m drop).
This option is expected to lower the water levels. We had not run the calculations to determine the extent of the water drop but it is expected that the lake will continue to fluctuate between high and low water levels. As the outlet channel would not be controlled, there should not be any impediment to fish movement.
Although stable moderate lake levels are desired, the extreme low levels will probably continue to result in concerns over water levels, property value, and mismanagement. Impacts of lowering the outlet channel will result in a slight increased overall carrying capacity of the channel.
Although the moderate annual increased loss of water from Sylvan Lake may not be highly significant in one season, this additional volume passed onto Cygnet Lake would need to be addressed.
Slide 19: Maintain Outlet
This option is somewhat similar to upgraded channel option in that the initial 125 m of the lake outlet is cleaned to increase the channel carrying capacity within this short reach. If you remember, channel modifications further downstream will not improve the overall carrying capacity so this option focuses on the initial 125 m of channel. The marked difference with this option is that the sill elevation is not lowered.
With this option, the channel capacity is maintained which would be relatively easy to accomplish.
There will be regular maintenance required and the lake levels will still naturally fluctuate. Impacts of the increased flows to Cygnet Lake will need to be evaluated. As indicated in the previous slides, even moderate benefits at Sylvan Lake can be significant at Cygnet Lake.
Page H10 of 12 Slide 20: Erosion Protection
We are now shifting from increasing the lake outlet capacity to mechanisms intending to adapt or cope with the high water levels. Erosion protection using rip‐ rap is a commonly used method to protect property and infrastructure around the lake. It is done by placing rock over a geotextile to protect the shoreline from erosion. We are also requiring the establishment of viable vegetation within the rip‐ rap which should enhance the long term effectiveness of the shoreline protection and offers fish habitat.
Some of the benefits include good shoreline protection with immediate effectiveness after installation (that is, no establishment period is necessary) and the rip‐rap heals itself if rocks are moved or displaced. As well, no fish habitat compensation is considered necessary (at this time).
This option will have no bearing on lake levels and can generally only be constructed during ice covered conditions. There are significant costs to the lot owner varying between $10,000 and $15,000 for a 20 m wide lot. Note that these are (very) conceptual cost estimates and actual costs may vary depending on the circumstance.
Retaining walls also offer good protection of the shoreline but with some differences. They also offer good protection immediately after installation but they involve more construction and engineering aspects. They have higher long term maintenance costs and vertical walls tend to deflect energy rather than dissipating it resulting in the possibility of erosion on neighboring properties. As well, retaining walls require fish compensation.
Slide 21: Natural Buffers
This option is equivalent to the status quo – to allow the lake to fluctuate and lakeshore protection by eroding buffers and allowing natural vegetation to protect the banks.
One key benefit of this option is that protection improves over time once vegetation establishes itself. Fish habitat is maintained or improved, and impacted areas will eventually heal and repair naturally. This is a very low cost item to implement compared to armoring. Protection can be enhanced with natural materials such as stakes and brush bundles.
The lake will still fluctuate and vegetated banks may be viewed as unsightly especially when the trees fall into the bank. It takes establishment time before vegetation is effective especially when lake levels are high. {Aside: an audience member pointed out that allowing erosion of natural buffers may not work in established subdivisions where infrastructure of lot ownership is to the bank}
Page H11 of 12 Slide 22: Conclusions
All outlet channels will have a finite carrying capacity. The Sylvan Creek is functioning as it is intended with no artificial restriction to the channel carrying capacity.
The lake levels are naturally high and part of the normal fluctuations between low and high water levels. The wet cool spring coupled with a high spring snowpack (as well as a healthy groundwater inflow) resulted in the recorded maximum water levels in August 2011.
The hydraulic control point of the outlet channel is at the lake outlet. The lake outlet is in a relatively natural state and it has not been silted in or blocked. The measured sill elevation is 936.7 m which corresponds quite well to previously reported sill elevations in 1978 and 2005 but not well to historic values.
Options are available to manage the water and manage the erosion from fluctuating water levels. Focusing on the outlet structure will take additional evaluation to refine the options and evaluate the costs and benefits. Lake focus options such as shoreline protection and, in particular, natural buffers are the favoured options even though they do not control lake levels.
Slide 23: Questions
Alberta Environment and Sustainable Resource Development intend to complete the following action items:
- Documenting the assessment in summary format incorporating questions and comments received during this and previous presentations; - Finalize the water management options summary matrix; - Forward finalized documents to municipalities as part of this presentation; - Asking the Sylvan Lake Management Committee to take on the former role of the Sylvan Lake Advisory Committee; and - Complete the water balance for Sylvan Lake to better assess the efficacy of potential improvement options.
Page H12 of 12 8/5/2012
Sylvan Lake Levels
July 10, 2012
Outlet Channel Assessment
• 2011 experienced highest recorded water levels; • 2012 levels still high; • Concerns received on outlet channel;
2
1 8/5/2012
Survey Reach • Outlet channel assessed;
• 1.1 km reach surveyed;
• Hydraulic control point between railway bridge and lake;
3
937.15
936.94
936.7
936.11
4
2 8/5/2012
5
6
3 8/5/2012
7
937.32
937.15
936.7
936.11
8
4 8/5/2012
Questions and Answers
• Is the outlet silted in or blocked? • Is the outlet channel causing the high lake levels? • Is Highway 20 impeding flow? • Is Cygnet Lake backing up the water? • What can be done?
9
Is the Outlet Silted or Filled in?
10
5 8/5/2012
Is it the Outlet Channel?
11
Stage Discharge Curves for Sylvan Lake
937.4
937.3
937.2
937.1
937.0
936.9 Elevation (m) Elevation
936.8
936.7 2012 Curve Pre-1988 Lower 936.6 1992 Curve Pre-1988 Upper 936.5 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Discharge (cms)
12
6 8/5/2012
Sylvan Lake Levels
937.40 937.30 937.20 937.10 937.00 936.90 936.80
936.70 Year 936.60 936.50 936.40 936.30 936.20 936.10 936.00 1910 1930 1950 1970 1990 2010 Elvation (m)
Is it the Road?
• Inverted Culvert; • 90o Bend; • Twin Culverts; • Rise at 800 m; • Train Bridge;
7 8/5/2012
Is Cygnet Lake Backing Up the Water?
15
Why not Control the Lake Water Elevation?
16
8 8/5/2012
What Can Be Done? (Options)
• Upgrade outlet channel; • Control structure; • Maintain outlet; • Erosion protection; • Natural buffers;Inputs Outputs
Lake
17
Control Structure
• Key Aspects: a control structure installed at the lake outlet with ability to control outflow at higher lake elevations, improved channel and infrastructure downstream; • Pros: control mechanism for lake levels, range of fluctuations reduced, shoreline stability enhanced; • Cons: complex operation plan is required and necessitate agreement with numerous stakeholders, annual maintenance required, greater expectation of control over high/low water levels, movement of fish impaired, increased flow expected at Cygnet Lake, extent of upgrades will need to be assessed, (very) conceptual cost estimate is approximately $1,500,000;
18
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Upgrade Outlet Channel
• Key Aspects: re-grade outlet to an elevation of 936.5 m, improve channel to Highway 20; • Pros: outlet channel upgraded and lake levels lowered, no impediment to fish movement, fish habitat potential maintained, no lake level operation necessary; • Cons: maintenance required on a regular basis, lake levels will still naturally fluctuate, perception of mismanagement will likely continue, impacts of increased flows to Cygnet Lake need to be evaluated, (very) conceptual cost estimate is in the order of approximately $100,000.
19
Maintain Outlet
• Key Aspects: improve lake outlet to Highway 20 but without lowering the natural lake elevation; • Pros: channel capacity will be maintained, relatively easy to accomplish, minimum capital investment required; • Cons: maintenance required on a regular basis, lake levels will still naturally fluctuate, impacts of increased flows to Cygnet Lake need to be evaluated.
20
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Erosion Protection
• Key Aspects: erosion protection to protect property and infrastructure. Rock armoring requires the establishment of viable vegetation • Pros: protection of toe and upper bank erosion, good protection after installation, good healing when rock is moved or displaced, easy to install and repair, fish habitat compensation is not necessary when shoreline is vegetated; • Cons: has no bearing on lake levels, access usually only in ice covered conditions, significant cost to the lot owner (very conceptual costs range about $10,000 to $15,000 for 20 m wide lot);
21
Natural Buffers
• Key Aspects: plants, possibly in combination with natural materials (lots, stakes, brush bundles) offer natural protection in combination with buffers that are naturally allowed to erode (setbacks, MRs). • Pros: protection grows stronger with age, relatively low cost and natural appearance, fish habitat is preserved, impacted banks heal and repair naturally, minimal cost compared to armouring; • Cons: lake will still fluctuate, vegetated banks may be viewed as unsightly, needs establishment time before vegetation is effective (banks may slump as they need time to establish before vegetation is mature enough to stabilize the banks); 22
11 8/5/2012
Conclusions
• Outlet channel is functioning as intended; • High lake levels naturally occurring; • Hydraulic control point at lake outlet; • Options include: OUTLET FOCUS: LAKE FOCUS: -Upgrading lake outlet; -Shoreline protection; -Control structure; -Natural buffers; -Maintaining lake outlet;
23
Questions
12
APPENDIX I ‐ FAQS
Sylvan Lake Water Level Assessment and Options October 2012 FFAAQQ
July 2012
Frequently Asked Questions: Sylvan Lake
Sylvan Lake is the jewel of Central Alberta as it is known for its natural beauty.
What are the basic facts about Sylvan Lake?
This outlet watercourse flows south easterly to Cygnet Lake through the Cygnet Lake Drainage District and ultimately into the Red Deer River. Its deepest point of 18 meters, makes it deeper than other local lakes such as Pigeon, Buffalo and Gull Lakes. The lake is a popular sport fishing destination for Walleye, Northern Pike and Lake Whitefish.
How do Sylvan Lake’s Water Levels Change?
Sylvan Lake is a natural water body which receives inflow from surface water and groundwater which aids in maintaining good water quality and clarity. The lake receives surface water inflow from several tributary watercourses. The water flows out through the outlet watercourse, Sylvan Creek, which is located on the east side of the lake. It is a small, fish bearing, watercourse. Most water loss on Sylvan Lake’s large surface area is due to evaporation. A combination of hot windy days creates the greatest evaporation which lowers lake levels.
The Water Cycle
What is the current and historical water level?
Sylvan Lake Recorded Water Levels (1955-2011) The attached graph Annual Minimum and Maximum Mean Daily shows Sylvan Lake’s mean
937.5 daily annual maximum 937.4 and minimum historic 937.3 water levels from 1955 to 937.2
937.1 present. The graph 937.0 shows the lake’s natural 936.9 fluctuating cycle of high 936.8 936.7 and low water years; and 936.6 when flows occur through Elevation (m) 936.5
936.4 the outlet watercourse.
936.3
936.2 The highest recorded 936.1 water level in 60 years 936.0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 was in August 2011 at Year 937.31m.
You can obtain daily water level readings from AB Environment and Sustainable Resource Development’s website: http://www.environment.alberta.ca/apps/basins/default.aspx.
What Can I Do? Environmental Reserves provide natural shoreline for wildlife habitat protection. The Environmental Reserve also provides protection of private property by providing a buffer between the water’s edge and your property line.
By stepping back from the water’s edge (at least 3 meters), and allowing deep‐rooted vegetation to grow (cattails, rushes, willow), the shoreline will be able to withstand wind and water erosion more effectively.
If you are experiencing erosion to your lakeshore and are exploring options to mitigate erosion, the following websites provide informative options:
Living By Water Erosion Protection http://www.livingbywater.ca/erosion.html
If you plan on carrying out activity that may impact the bed and shore, check with your local municipality as well as Red Deer’s Alberta Environment and Sustainable Resource Development office and Fisheries and Oceans Canada in Edmonton as they are the administrators of environmental legislation. The following fact sheet provides further information.
Water Act Shoreline Modification Fact Sheet http://environment.alberta.ca/documents/Water‐Act‐Shoreline‐Modification.pdf
The Shore Primer http://www.dfo‐mpo.gc.ca/regions/central/pub/shore‐rivages‐pr/pdf/shore‐rivages‐pr_e.pdf
APPENDIX J ‐ COMMENTS ON DRAFT ASSESSMENT
Sylvan Lake Water Level Assessment and Options October 2012 A draft Sylvan Lake Water Level Assessment and Options was forwarded to the Sylvan Lake Management Committee on August 20, 2012 for comments and feedback. Below are the comments and ESRDs consideration and response to the comments received. Some comments resulted in changes to the document itself whereas others are taken as general comments or not within the scope or purpose of the original assessment.
The comments received were stripped of any aspect that made the source identifiable to maintain the anonymity of the original author. While it is expected that none would object to having identifying comments included, it is enot german to the assessment to include these and, as such, they were removed without changing the context of the comments.
Also attached is a secondary table that was attached to some of the comments to assist in providing a more comprehensive comment.
No. Comment Received Response 1 I think the report was well done. 2 I don’t have any changes to add to your report other Agreed. TOC added to final report. than a formatting request to add a table of contents. 3 I think this [high water level] is a natural occurrence Agreed. The lake is expected to continue to fluctuate and the lake level will recede in time. naturally around the mean water levels. 4 I think what you said about groundwater entering Agreed. Groundwater is believed to be a significant may be very true as there was little or no runoff this contribution to the base flow into the lake. This year and lake levels remained high. results in an overall higher water level in Sylvan Lake. 5 I am not in favor of putting in any water control The Sylvan Lake Management Committee or, devices. ultimately, its member municipalities will need to collectively determine the preferred option. This includes construction and operation of any water management control structures. One option is to continue to allow the lake to naturally fluctuate. 6 The impact of lowering the lake would have For any water management control structure, an significant impact on downstream landowners. environmental evaluation of impacts to downstream landowners, lake residents and the environment must be completed. It is agreed that there is potential for downstream impacts depending on water management control option installed and how it is operated. Significant public consultation would need to be undertaken especially where the potential for impact exists.
The Cygnet Lake control structure was constructed in 1999 with the intent of receiving greater flow from Sylvan Lake. Any water management control structure design (and operation) would need to be
Page J1 of 14 No. Comment Received Response consistent with the design capacity of the Cygnet Lake control structure. 7 Riparian damage seems to be affecting the summer villages most. 8 If we go ahead with another study, spending a lot of resources, the lake level may be down by the time we are finished the study. 9 In general terms, we have no concerns with either the assessment or the options presented relative to the outlet and downstream channel. 10 It appears that the most significant reasons for the Agreed. High lake levels are believed to be a result of high water level in Sylvan Lake are the reduced higher inputs from increased precipitation, increased percolation levels due to high moisture runoff (partly due to saturated soil conditions) and a content/groundwater saturation and siltation. net groundwater flow into the lake. This is in combination with lower evaporation rates.
The scope of the assessment mainly focuses on Sylvan Creek itself and does not examine in depth the potential reasons for high water levels in Sylvan Lake. 11 As no specific items have been identified which could A water balance model is currently under have played a causal role in the current lake level, it development by ESRD and is nearing completion. is our recommendation that no further action be Once this work is complete, the long term efficacy of taken to study/modify either the outlet channel or various water management options can then be the lake water level itself. evaluated.
Identification of the various scenarios for water management options will be developed in consultation with the Sylvan Lake Management Committee. 12 While it is acknowledged, that the past few years The riparian health of the shoreline was not assessed may not represent the most desirable water levels as part of the assessment. from a social or economic perspective, Sylvan Lake, like any other natural water body, is likely subject to Recent visual observations of the shoreline indicates experience a wide variety of natural fluctuations and that there is some impacts to vegetation due to the the actual health of the lake does not appear to have high water levels but this is a natural process and it is been compromised. expected that the vegetation will eventually reestablish. This is a functional part of the normal cycle of the riparian shoreline. 13 Overall I found that it summarizes the Sylvan Lake situation well, puts it into historic perspective and explains the range of options for lake level control. 14 The attached table highlights the natural variability of The table is included below for reference.
Page J2 of 14 No. Comment Received Response precipitation and evaporation that are important inputs to any decision on attempted control of Sylvan Lake level. 15 Our basic position on this matter is that the inventory Ecological value is a concept sometimes used to of water in Sylvan Lake is part of the surface and quantify the value or benefit derived from natural subsurface natural capital of the watershed. Up to resources. $12 billion might be flushed down the Red Deer River to Saskatchewan in an attempt to see a community Water currently stored in Sylvan Lake has future beach emerge froms today’ Sylvan Lake’s fish habitat. value when the water levels will eventually recede. The stored water will keep the lake higher than it otherwise would have been had a portion of the water been artificially released. The water balance currently under development is intended to quantitatively assess the glon term benefits and impacts for each of the water management options. 16 [We] recommend responsible water resource Agreed. The Sylvan Lake Management Committee or, management. ultimately, its member municipalities will need to collectively determine the preferred option. 17 Watershed occupants who may be temporarily inconvenienced by the historically high water level can continue to speak for themselves. 18 (pp1) The report states: “The Sylvan Lake mean annual precipitation and evaporation are 515 mm and 685 mm respectively…”
The lake mean annual precipitation and evaporation Typically, lakes in this part of the province have a numbers require an explanation. Cumulative higher mean annual evaporation compared to the evaporation cannot exceed precipitation over the mean annual precipitation. The water balance is area of the watershed without long term net maintained due to additional inflow from streams depletion of the water inventory. Data in the AXYS within the lake watershed and groundwater. report suggest the same conclusion. It would be better to present the precipitation‐evaporation data Historic monthly precipitation and evaporation data for the total area of the watershed, however, that’s for Sylvan Lake is required for the water balance almost impossible without real data. model for the watershed as a whole.
One key indicator is that the concentration of There is a small amount of variance (uncertainty) conserved ions in the lake water (e.g. sodium and about the mean values. However, a reasonable chloride) are relatively constant and do not increase water balance model can still be developed with the with the net loss of water by evaporation. So there is available data using standard hydrological methods. a large uncertainty about what is actually happening. The relative constant ions are a reflection of long term steady state conditions within the lake. The annual level fluctuations are small compared to the
Page J3 of 14 No. Comment Received Response large lake volume resulting in relatively stable ions once steady state conditions are reached. 19 (pp1) The report states: “…net groundwater flow into (or from) the lake is not well understood at this time.”
The AXYS 2005 evidence is that the net flow of Alberta Environment and Sustainable Resource subsurface groundwater is about the same as the Development is currently in the process of lake outflow. developing a calibrated water balance model for Sylvan Lake. The model includes an estimate of the groundwater contribution. The model is needed to quantitatively evaluate the efficacy of alternate water management scenarios. 20 (pp2) The report states: “Over the years, channel improvement and realignment projects were undertaken…”
The controversy is about whether the changes were The context of the term “improvement” is from a actually “improvements.” hydraulic conveyance capacity viewpoint only. It is believed that the routing of Sylvan Creek along the west side of Highway 20 resulted in an improvement in channel conveyance capacity. The newer channel is straighter, shorter, smoother, has a slightly greater slope and is relatively maintained resulting in improved conveyance capacity compared to natural conditions. 21 (pp2) The report states: “A large portion of the shoreline wetland on the southeast end of the lake has been infilled…”
Anecdotal evidence suggests that Sylvan Creek flow Agreed. The pre‐1988 stage‐discharge curve (Figure at a previous historical high water level in 1955 5 of the assessment) indicates that Sylvan Creek (some lake residents do remember that far back) was flowed at approximately 28 cfs or 0.8 m3/s when the significant even with the original channel lake was at an elevation of 937.25 m. This is configuration. somewhat comparable and slightly lower than the current hydraulic conveyance capacity.
A model simulation can be done to reproduce the pre‐1988 rating curve shown in Figure 5. However, there is sufficient confidence in the original rating curve to assess Sylvan Creek. 22 (pp3) The report states: “The lake outlet appears to
Page J4 of 14 No. Comment Received Response be subject to siltation and degradation…”
The winter season is usually forgotten in these Agreed. Ice ridges can naturally scour and form discussions. Ice heave at high water can contribute ridges. Since the sill elevation has been relatively to more channel blockage than summer stable from at least 1978, it does not appear to be a sedimentation. significant factor in the last three decades in the vicinity of the outlet. However, it may explain the difference between the sill elevation between the 1920s and 1978. 23 (pp8) The reports states: “The shoreline wetland has been significantly infilled in 1993 constraining the outlet to a 35 m strip.”
The great geotechnical question is whether ground The surveyed sill elevation appears to be relatively creep after loading the area with landfill has caused stable since at least 1978 prior to the infilling of the the channel to alter its elevation. At the least, the wetlands in 1993. The historic information available landfill probably forced dewatering of the original does not support ground heaving or channel silting in wetland. from the fill adjacent to the channel. Dewatering of the original wetland has definitely occurred. 24 (pp8) The report states: “An improvement in channel conveyance capacity is considered when the water flow rate increases for the same lake elevation.”
Does this statement apply to just the ice‐free season, This assessment focused on the ice‐free season and or to the period in which flow is restricted by an ice ESRD model runs produced only open water stage‐ cap on the channel? Groundwater inflow should be discharge curves. Winter observation (Nov 2011) continuous during the 12 months but surface outlet indicates some sub‐ice flow when the water levels flow is likely reduced in winter. are sufficiently high.
Although this may slightly limit the robustness of the water balance model, it does not have a significant implication on the conclusions of this assessment. 25 (pp11) The report states: “The 1991/92 stage‐ discharge curve matches closely to the 2012 curve suggesting that the infilling has not had a significant impact on the overall channel capacity.
This statement is the critical conclusion. Without Additional flow monitoring could improve the reliable flow monitoring of the creek it is hard to precision of the model prediction for the 2012 stage‐ confirm the hydraulic analysis. discharge curve; however, it is not felt necessary to repeat or augment the flow analysis as the results of the MPE report were felt reasonable.
Page J5 of 14 No. Comment Received Response
A model simulation can be done to reproduce the pre‐1988 rating curve in Figure 5. However, there is sufficient confidence in the original rating curve to assess Sylvan Creek. This is based on: a) the confidence in the individuals completing the Sylvan Lake – Regulation by Outlet Control hydrology report attached in Appendix B of the Sylvan Lake‐Cygnet Lake Study (1994); and b) The flowrate values are in general agreement of what one would expect from a completely natural channel. 26 (pp12) The report states: “AXYS Environmental Consultants Ltd. Estimated the water balance for Sylvan Lake for the period 1956 to 2000…”
The total lake volume is more than 420 million cubic Agreed that the Town of Sylvan Lake’s water meters so the annual Sylvan Creek outflow number is withdrawals can also be considered water removed a tiny fraction of the total. In fact the volume is in from the system. This export mechanism is a the same range as the Town of Sylvan Lake consideration of the water balance model currently groundwater withdrawal for domestic and industrial under development. use. That is a watershed export mechanism too. 27 (pp12) The report states: “A cool wet spring is believed to be the most significant factor in the high lake levels in 2011.”
I live on Golf Course Creek and observe the tributary Agreed. This comment is consistent with this inflow daily. I’d say the 2011 level was dominated by assessment although the scope was to evaluate the monsoon season. Cold surface water through the Sylvan Creek rather than look at possible early ice‐free low‐evaporation season was a explanations for the high lake levels. secondary factor. Check the 2011 lake level rate change curve for data. 28 (pp12) The report states: “Sylvan Lake has been experiencing a water level trend increase.”
The year‐to‐year changes in precipitation and Agreed. A water balance model is currently under evaporation typically have been large and erratic. development by ESRD and is nearing completion. Observable lake level is the net result. I would not Once this work is complete, the long term efficacy of design a lake level control system without having a various water management options can then be better handle on the long term statistics. evaluated.
29 (pp12) The report states: “It is not clear if any
Page J6 of 14 No. Comment Received Response particular event occurred that is causing the lake levels to steadily increase over the past 50 years.”
Urbanization of the watershed has altered The changes to the water balance by development infiltration, recharge and discharge areas, within the watershed are outside of the scope of this impermeable surfaces and watershed surface flow. assessment. These are a consideration of the water Don’t leave the impact of population growth out of balance model currently under development. the explanation. 30 (pp12) The report states: “This is based on gridded precipitation data which has been gapped filled from nearby climate station records…”
Single or multi‐station records seem to follow a Agreed that the best data comes from Sylvan Lake similar pattern. No data set will be perfect because itself; however, this analysis uses the best data of the nature of patchy rainfall in this region. The available. best rainfall gauge is still Sylvan Lake itself. 31 (pp14) The report states: “The capacity of the existing constructed channel is better than the historic natural channel capacity…”
The potential for flow through Sylvan Creek is still Agreed that Sylvan Creek as a finite natural hydraulic small for instantaneous level control application. It conveyance capacity. The majority of water lost from would be helpful to relate the natural flow rate to Sylvan Lake is though evaporation. The comment that required to maintain the lake level at a setpoint also suggests a potential scenario to be evaluated. after periods of high rainfall. That is, what outflow This scenario will be considered as part of the rate would be required for a 5 cm rain? quantitative analysis once the water balance model is complete. 32 (pp 15) The report states: “Groundwater is believed to be a significant flow contribution in the lake.”
Groundwater flow is more or less constant, Once the water balance model work is complete, the depending on the condition of the aquifers that drive model will also provide an estimate of the it. Monitoring wells and the Town of Sylvan Lake groundwater contribution. wells should provide an indication of significant changes in groundwater flow. 33 (pp16) The report states: “Options to manage water levels focus on decreasing inflow, increasing outflow or adaptation within the lake itself.”
The Town of Sylvan Lake stormwater management Agreed. The Town of Sylvan Lake has constructed practice already captures and diverts significant curbs and gutters along Lakeshore Drive in the surface water outside the watershed and into the Cottage and Centennial Park areas. This channels Red Deer River via Cygnet Lake. Expansion of the
Page J7 of 14 No. Comment Received Response Town of Sylvan Lake population will further decrease surface runoff from directly entering the lake and that flow into the lake unless major attention is given eventually discharging into Sylvan Creek. This work to construction of new wetlands. was completed in 2008. Future changes to the watershed should assess, using the water balance model currently in development, the long term water levels in the lake to ensure changes will not be individually or cumulatively significant. 34 (pp16) The report states: “Options for increasing outflow generally focused on the outlet channel.”
The water inventory of Sylvan Lake is part of the Understood. The ecological value of the water may watershed natural capital. Each cubic meter of water be used as a measure. The Sylvan Lake Management has value which, if exported, decreases the asset Committee or, ultimately, its member municipalities value of the resource. Furthermore, arbitrarily will need to collectively determine the preferred dropping the lake level transfers costs to other option which may include the ecological value of the property owners. natural resources of Sylvan Lake. One option is to continue to allow the lake to naturally fluctuate. 35 (pp16) The report states: “Any alteration of the outlet, with an intended purpose of affecting Sylvan Lake levels, is of concern from an environmental perspective…”
The Cumulative Effects Management System in idem principle has the capability to provide the physical and economic analyses that are inputs to a decision of this nature. The municipal decision making process is itself a contributor to watershed risk. Sylvan Lake is a public asset that is not included in whole or in part on any financial statements of the watershed municipalities. 36 (pp17) The report states: “A water balance model for Sylvan Lake is currently being finalized that would be used to evaluate the long term benefit of various options.”
The water balance model under development The comment suggests a potential scenario to be excluded the major pipeline infrastructure evaluated. This scenario will be considered as part of components (for water supply from the Red Deer the quantitative analysis once the water balance River) and net groundwater export (with sewage model is complete. transport) to the City of Red Deer for processing. That infrastructure will further affect the water balance of the Sylvan Lake watershed and should be treated as a high‐risk venture both environmentally
Page J8 of 14 No. Comment Received Response and economically. 37 (pp17) The report states: “The control structure would increase the outflow from the lake.”
Given the historic pattern of Total Precipitation on Agreed. The lake will still fluctuate even with a water the watershed, any attempt to manually control the management control structure. The lake will always level of Sylvan Lake will expose the water inventory be either higher or lower than the sill elevation of the to a lottery. Even a cursory examination of the year‐ lake. to‐year precipitation record will quickly show that rain/snowfall and weather‐controlled evaporation in successive years are not correlated. If an operating goal is to set the lake level in any year at the
statistical midpoint for any month (say, 937.6 masl on July 01) then it is probable that the following year will be outside the desired control range.
To express that outcome another way: Any amateur control technique is doomed to fail. Once it is A water balance model is currently under released downstream, Sylvan Lake’s water inventory development by ESRD and is nearing completion. will be gone forever. Once this work is complete, the long term efficacy of various water management options can then be evaluated. 38 (pp18) The report states: “The level of Sylvan Lake can be adjusted by a control structure (as described in the previous option)…”
A knowledgeable member commented: The Sylvan Lake Advisory Committee recommended (Appendix B) a variable control structure with a 2 “The Sylvan Lake Advisory Committee reported in m3/s capacity at 937.0 m water elevation. 1994 that: The Sylvan Lake Management Committee or, “A natural outlet from Sylvan Lake is the ultimately, its member municipalities will need to preference of a majority of stakeholder groups” collectively determine the preferred option. It is anticipated that they will consider the viewpoints of I believe this is still the case, in spite of a large, vocal all residents within their respective municipalities. group advocating lowering the lake by whatever means. It is my opinion that the majority of that group do not have the information necessary, or understand the parameters affecting lake level fluctuation.” 39 (pp18) The report states: “The sill elevation would remain at 936.7 m.”
Page J9 of 14 No. Comment Received Response The historic Sylvan Lake average seasonal high water The current (natural) sill elevation is currently at level on July 01 is about 936.7 masl. So a sill level set 936.7 m. This option (Maintain Outlet Channel) at the same elevation as that maximum would allow proposes to straighten and remove vegetation and for minimal flow into Sylvan Creek. debris but not change the current sill elevation of the lake outlet. See AENV (now ESRD) data posted here: http:// sylvanlakewatershed.wordpress.com/2012/07/ 18/sylvan‐lake‐evaporation‐rate/ 40 (pp19) The report title states: “Erosion Protection (Armoured Shoreline or Retaining Walls)”
Significant shoreline damage also occurs from ice Agreed. Ice heave also causes shoreline damage. heave during the winter months. That point should Higher water levels are expected to exacerbate be taken into account as part of the failure of banks, shoreline damage resulting from ice heaving as well. bushes and trees especially in undeveloped environmental and municipal reserves has been caused by ice pressure, and aggravated by open water erosion. 41 (pp19) The report states: “Erosion protection focuses on protecting the shoreline and infrastructure…”
If owners are responsible for their properties then The Sylvan Lake Management Committee or, Alberta or the watershed municipalities have no ultimately, its member municipalities will need to reason to fund preventative or remedial maintenance collectively determine the preferred option. This of the Sylvan Lake shoreline. No case has yet been includes construction and operation of any water presented for subsidization of shoreline stabilization management control structures. Erosion protection projects on private property. (armored shoreline or retaining walls) on individual lots are the responsibility of the individual. 42 (pp20) The report states: “Fish compensation is necessary as…”
A Sylvan Lake resident and long time active fisherman This facet has not been captured. Evaluating the advised that one consequence of the destruction of impacts to fish habitat by the infilling of the shoreline the Sylvan Creek wetland by the developer was the wetland is outside of the scope of this assessment. elimination of a critical fish habitat. That consequence has not been described in evidence presented in this report.
The Sylvan Lake fishery is part of the watershed’s As part of any water management control option, natural capital and requires valuation as a function of impacts to fisheries are a critical evaluation any proposal to adjust the lake water level set point. component. Where there is unavoidable impact to fisheries, compensation is necessary so that there is no net loss of fish habitat.
Page J10 of 14 No. Comment Received Response 43 (pp21) The report states: “The lake levels are naturally high and part of the normal fluctuations…”
The historical record of water levels on July 01 is 936.7 meters above sea level (masl) plus or minus 0.35 meter.
That is, the lake level can vary from year to year in a
0.7 m (about 2 feet) range. The area of Sylvan Lake is about 42 square kilometers so a 0.3 m depth (about 1 foot) contains about 12 million cubic meters of water.
If that volume of water flowed out of the lake at a constant rate of 1 cubic meter per second it would Understood. The ecological value of the water may take 12 million seconds, or 139 days. The discharge be used as a measure. The Sylvan Lake Management curve suggests that the Sylvan Creek channel might Committee or, ultimately, its member municipalities allow a 20% higher flow so the drainage time might will need to collectively determine the preferred be reduced at optimum conditions. option which may include the ecological value of the natural resources of Sylvan Lake. 12 million cubic meters of water is equivalent to 8 years of well water supply for the Town of Sylvan Lake. 44 (pp21) The report states: “The following action items are to be followed up with by…”
It is recommended to include a fourth action item: d) The Sylvan Lake Management Committee or, Work with the Sylvan Lake Watershed Stewardship ultimately, its member municipalities will need to Society and its 440 members and property owners to collectively determine the preferred option. The survey public opinion on technical alternatives for municipalities represent their constituents and will management of the fate of the Sylvan Lake determine the selection criteria including optimum watershed. consultation approach.
Total Precip Preciptation Evaporation Difference Date (mm) m3 (mm) Evap mm3 (Mm3) (Precip-Evap, Jan-56 16.1 672175 0 0 Mm3) Feb-56 16.4 684700 0 0 Mar-56 46.2 1928850 0 0
Page J11 of 14 Apr-56 19.7 822475 41.3 1724275 May-56 11 459250 134 5594500 Jun-56 149 6220750 151.8 6337650 Jul-56 46.6 1945550 135 5636250 Aug-56 61.9 2584325 118.9 4964075 Sep-56 26.4 1102200 84.1 3511175 Oct-56 18.6 776550 52.2 2179350 Nov-56 3.6 150300 0 0 Dec-56 42.4 1770200 0 0 457.9 19117325 717.3 29947275 -10.8
Jan-57 20.4 851700 0 0 Feb-57 21.6 901800 0 0 Mar-57 27.8 1160650 0 0 Apr-57 33.7 1406975 39 1628250 May-57 50.8 2120900 134.3 5607025 Jun-57 80.1 3344175 136.2 5686350 Jul-57 37.6 1569800 177.3 7402275 Aug-57 79.6 3323300 136.4 5694700 Sep-57 25.3 1056275 121.5 5072625 Oct-57 60.3 2517525 48.2 2012350 Nov-57 15.5 647125 0 0 Dec-57 4.7 196225 0 0 457.4 19096450 792.9 33103575 -14.0 Jan-58 32.8 1369400 0 0 Feb-58 23.2 968600 0 0 Mar-58 41.1 1715925 0 0 Apr-58 10 417500 45.7 1907975 May-58 47.4 1978950 148.2 6187350 Jun-58 89.2 3724100 138.5 5782375 Jul-58 85.7 3577975 140 5845000 Aug-58 29.6 1235800 165.4 6905450 Sep-58 49.8 2079150 121.2 5060100 Oct-58 3.3 137775 77.2 3223100 Nov-58 32.3 1348525 0 0 Dec-58 17.8 743150 0 0 462.2 19296850 836.2 34911350 -15.6 Jan-59 39.5 1649125 0 0 Feb-59 13.9 580325 0 0 Mar-59 19.3 805775 0 0 Apr-59 31.5 1315125 70.8 2955900 May-59 30.1 1256675 134.5 5615375 Jun-59 83.3 3477775 154.9 6467075 Jul-59 116.6 4868050 182.6 7623550 Aug-59 54.5 2275375 146.7 6124725 Sep-59 22.8 951900 111.7 4663475 Oct-59 27 1127250 52.1 2175175
Page J12 of 14 Nov-59 18.1 755675 0 0 Dec-59 24.1 1006175 0 0 480.7 20069225 853.3 35625275 -15.6 Jan-89 25.9 1081325 0 0 Feb-89 21.5 897625 0 0 Mar-89 3.6 150300 0 0 Apr-89 22.1 922675 42.8 1786900 May-89 54.2 2262850 118.7 4955725 Jun-89 76.9 3210575 146.4 6112200 Jul-89 61.2 2555100 143.2 5978600 Aug-89 94.2 3932850 111 4634250 Sep-89 33.2 1386100 99.3 4145775 Oct-89 41.1 1715925 53.7 2241975 Nov-89 22.7 947725 0 0 Dec-89 14.7 613725 0 0 471.3 19676775 715.1 29855425 -10.2 Jan-91 8.7 363225 0 0 Feb-91 22.9 956075 0 0 Mar-91 14.8 617900 0 0 Apr-91 17.4 726450 60.8 2538400 May-91 99.3 4145775 111.9 4671825 Jun-91 143.8 6003650 114.1 4763675 Jul-91 77.3 3227275 139.3 5815775 Aug-91 122.7 5122725 126.1 5264675 Sep-91 27.5 1148125 99.9 4170825 Oct-91 46.9 1958075 52.7 2200225 Nov-91 12 501000 0 0 Dec-91 6.9 288075 0 0 600.2 25058350 704.8 29425400 -4.4 Jan-93 5.5 229625 0 0 Feb-93 10.6 442550 0 0 Mar-93 25.4 1060450 0 0 Apr-93 30.4 1269200 48.1 2008175 May-93 45.2 1887100 140.3 5857525 Jun-93 104.4 4358700 151.1 6308425 Jul-93 98.4 4108200 140.1 5849175 Aug-93 46.1 1924675 126.4 5277200 Sep-93 27.8 1160650 106.5 4446375 Oct-93 12.7 530225 58.2 2429850 Nov-93 24.6 1027050 0 0 Dec-93 9.9 413325 0 0 441 18411750 770.7 32176725 -13.8 Jan-94 46.7 1949725 0 0 Feb-94 9.5 396625 0 0 Mar-94 13 542750 0 0 Apr-94 2.4 100200 66.3 2768025 May-94 74 3089500 133.1 5556925
Page J13 of 14 Jun-94 96.5 4028875 148.8 6212400 Jul-94 77 3214750 157 6554750 Aug-94 116.9 4880575 139.7 5832475 Sep-94 78.3 3269025 102.3 4271025 Oct-94 25.1 1047925 54.6 2279550 Nov-94 8 334000 0 0 Dec-94 10.8 450900 0 0 558.2 23304850 801.8 33475150 -10.2 Jan-98 18.8 784900 0 0 Feb-98 0 0 0 0 Mar-98 19.7 822475 0 0 Apr-98 27.6 1152300 53.2 2221100 May-98 58 2421500 137.4 5736450 Jun-98 121.2 5060100 120.9 5047575 Jul-98 58.8 2454900 125.9 5256325 Aug-98 59.8 2496650 143.7 5999475 Sep-98 26.2 1093850 106.4 4442200 Oct-98 52.8 2204400 43.4 1811950 Nov-98 20.2 843350 0 0 Dec-98 23.1 964425 0 0 486.2 20298850 730.9 30515075 -10.2 Jan-00 14 584500 0 0 Feb-00 11.8 492650 0 0 Mar-00 17.8 743150 0 0 Apr-00 25.9 1081325 51.1 2133425 May-00 43.7 1824475 111.8 4667650 Jun-00 118.1 4930675 129.8 5419150 Jul-00 164.4 6863700 126.8 5293900 Aug-00 49.8 2079150 121.7 5080975 Sep-00 25.3 1056275 86.2 3598850 Oct-00 6.4 267200 51.4 2145950 Nov-00 8.6 359050 0 0 Dec-00 21.6 901800 0 0 507.4 21183950 678.8 28339900 -7.2
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