LCI LACAS CONSULTANTS INC. CONSULTING ENGINEERS - HYDROLOGICAL SPECIALISTS, SINCE 1991

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1 LCI LACAS CONSULTANTS INC. CONSULTING ENGINEERS - HYDROLOGICAL SPECIALISTS, SINCE 1991 TECHNICAL MEMORANDUM DATE: February 6, 2012 TO: FROM: Cori Barraclough, R.P.Bio. Aqua-Tex Scientific Consulting Ltd. Brian LaCas, P.Eng. LaCas Consultants Inc. HYDROLOGICAL REVIEW 1. INTRODUCTION As per the request of Aqua-Tex Scientific Consulting Ltd. (Aqua-Tex) this report was prepared for the City of Kimberley (Client) by LaCas Consultants Inc. (LCI) which relates to Lois and Kimberley Creeks at Kimberley, BC. The purpose of this technical memorandum is to provide a hydrological review of Lois and Kimberley Creeks with respect to flooding impacts and a possible diversion of flows (Figure 1). 2. SCOPE OF WORK This assignment has the following scope of work: discussions with Client, City of Kimberley and Aqua-Tex; carry out hydrological modeling to determine the 2, 10, 20, 50, 100 and 200-year flood flows on both Lois Creek and Kimberley Creek; carry out a site visit of the creeks, Morrison subdivision and the intake works on Kimberley Creek for the diversion pipe through the City of Kimberley; provide an opinion on the existing diversion scheme; and prepare a technical memorandum. 3. HYDROLOGY Located in Kootenay Valley, Kimberley Creek is one of the major tributaries of Mark Creek, and it has a drainage area of approximately 25 km 2 at its mouth. Lois Creek is a tributary of Kimberley Creek, and it has a drainage area of approximately 11 km 2 at its Suite Howe Street Vancouver B.C. Canada V6Z 2P3 T: F: LaCas-Consultants.com

2 mouth. The median basin elevations of the Kimberley Creek and Lois Creek watersheds are approximately 1300 m and 1400 m, respectively. There are a number of hydrometric stations on Mark Creek, but most of them are designated as regulated. There is a hydrometric station on Mark Creek (08NG085) with a relatively long period of record, measuring natural flows, and it was operated by Water Survey of Canada (WSC) from 1989 to 1998 and has been operated by the City of Kimberley since Historical hydrometric data from this station was obtained both from the Water Survey of Canada and from available Mark Creek resource inventory reports. The Water Survey of Canada has one natural hydrometric station on Kimberley Creek near Kimberley (08NG057), but this station was only operated from 1968 to 1973 and has limited peak flow data. Other useful regional hydrometric stations operated by the WSC include the Mather Creek below Houle Creek (08NG076), St. Mary River below Morris Creek (08NG077), and St. Mary River near Marysville (08NG046). The hydrometric stations used in this study are listed in Table 1. Table 1: Regional Hydrometric Stations Station ID Station Name Drainage Area (km 2 ) 08NG046 ST. MARY RIVER NEAR MARYSVILLE 08NG076 MATHER CREEK BELOW HOULE CREEK 08NG077 ST. MARY RIVER BELOW MORRIS CREEK 08NG085 MARK CREEK ABOVE DIVERSIONS Period of Record Years of Peak Flow Data Status Daily, 20 Instant. Active Daily, 38 Instant. Inactive Daily, 35 Instant. Inactive Daily, 25 Instant. Inactive By analyzing available peak flow data at the Mark Creek hydrometric station (08NG085), it was determined that peak flows in the study area usually occur in May or June, as a result of snowmelt. Four methods were applied in determining the flood estimates for various return periods at two points of interest carried out by EBA Engineering Consultants Ltd. and reviewed by LaCas Consultants Inc.: Location 1 Kimberley Creek at its mouth (approx. 25 km 2 ) Location 2 Lois Creek at its mouth (approx. 11 km 2 ) Method 1: Station Frequency Analysis Method A flood frequency analysis was performed based on the historical maximum instantaneous flow record available at the Mark Creek hydrometric station (08NG085) using Environment Canada s Consolidated Frequency Analysis (CFA) software version 3.0. The distributions PAGE 2 OF 10

3 providing the best fit to the data record were selected in estimating the floods for various return periods at the station. Results of the station frequency analysis were then transposed to the project site drainage areas by the applying accepted watershed scaling methods. Method 2 Regional Analysis with Index Flood Method The regional analysis in this case involves the application of an index flood method. Flood frequency analyses were conducted for the four selected regional hydrometric stations. To make use of all available peak flow data, the maximum instantaneous flow records were extended by applying an average ratio of maximum instantaneous to maximum daily flows for the three largest floods at the stations. The distributions providing the best fit to the extended data records were selected in estimating the floods for various return periods at the stations. Results of the frequency analyses were then used in the index flood method, using the 10-year flood as the index flood. A relationship was determined between the unit index flood discharge (L/s/km 2 ) and drainage area. An envelope curve was then drawn to determine the unit 10-year flood at each site. The median ratios for various return period floods to the index flood were calculated from the regional flood frequency analysis. These ratios were used to determine the peak flood estimates for various return periods at the points of interest. Method 3 Regional Analysis with Design Flood versus Drainage Area Method In addition, plotting the flood estimates against drainage area using results of the frequency analyses from the four selected hydrometric stations yields a set of regression relationships. These regression equations were used in determining the flood estimates for various return periods at the points of interest. Method 4 - Streamflow in Kootenay Region Envelope Curve For comparison purposes, the 2002 Streamflow in Kootenay Region Envelope Curve prepared by the BC Ministry of Environment, Land and Parks was also used as a reference. In this regional study, a design curve for the 10-year peak flow as a function of drainage area was developed for Eastern Kootenay Region (Subzone Y). The regional median ratios of the flood estimates for various return periods to the 10-year floods were then applied. Peak Flood Estimates The peak flood estimates obtained from the four methods were compared, and results indicate that the estimates determined from the station frequency analysis with the shortest period of data record available are generally the lowest. The index flood method provides the second highest flood estimates, slightly lower than the estimates obtained from the 2002 Streamflow in Kootenay Region Envelope Curve. As a reasonably conservative approach, the peak flood estimates determined from the index flood method are recommended. Table 3 below presents the recommended flood estimates for various return periods at each point of interest. PAGE 3 OF 10

4 Return Period (yrs) Kimberley Creek Lois Creek Reference: Ministry of Environment, Lands and Parks, Report on British Columbia Streamflow Inventory. Streamflow measurements have been taken on both Kimberley Creek and Lois Creek by Aqua-Tex which will add to the database of flows in both watersheds. The data collected indicates that the flows in Kimberley Creek are roughly double of the flows in Lois Creek confirming the above analysis. The data collection should be carried out for at least the next 10 years to increase the database to enhance the statistical analysis and understanding of both creeks. 4. HYDROLOGICAL IMPACTS The Kimberley Creek watershed is an actively logged watershed which in recent years has had significant mountain pine beetle infestation. Studies 1,2 have shown that pine tree beetlekill may tend to increase the annual water yield in an affected watershed for decades to come. While studies are continuing to better understand the impacts of beetle-kill; according to Streamline 3 : it may be advantageous to focus research on approaches to accelerate hydrologic recovery, rehabilitation of salvaged areas, and water use by young stands and understory vegetation. Large scale removal of trees from the Lois and Kimberley Creek watersheds may also increase peak runoff both creeks; which in turn could exacerbate the flooding in lower Kimberley Creek. 5. KIMBERLEY CREEK DIVERSION In the 1950 s Kimberley Creek was put into an underground storm sewer system under the City of Kimberley. At the upstream end a 1,200 mm diameter culvert intake directs water into the storm sewer 1.6 km before emptying into the Mark Creek flume just downstream of the Wallinger Road bridge. 1 Bethlahmy, N More streamflow after bark beetle epidemic, Journal of Hydrology 23: Love, L.D The effect of streamflow of the killing of spruce and pine by the Engelmann spruce beetle. Transactions of the American Geophysical Union 36: Reference L L. Uunilla, and B. Guy, 2006 Streamline 3 Watershed Management Bulletin Vol. No. 9/No.2 Spring Issue. PAGE 4 OF 10

5 It is understood that in the past flooding has occurred upstream of the intake when the flow capacity of the culvert was exceeded during flood events. There is no existing engineered overflow channel to take the excess flow. Based on a cursory review, the capacity of the existing Kimberley stormwater diversion will not pass the 2-year peak flood in Kimberley Creek (including the 2-year peak flood on Lois Creek). Any debris blockage at the intake will further reduce the hydraulic capacity of the intake. Kimberley Creek augments flow in the Mark Creek flume. A cursory review of the Mark Creek flume indicated that the flume is past its service life and any additional diversion of water into the flume would not be advisable. Therefore consideration should be given to retiring the Kimberley Creek intake and replacing it with an open channel diversion around the flume. In June 2011, a reconnaissance of possible diversion routes were carried out and the recommended route (subject to some alignment alterations) is proposed in Figure 3 (Sheets 1 and 2). The route would take advantage of the peak flow attenuation in Taylor s Slough and avoiding the Mark Creek flume. The downstream end of the project is at the existing undersized 750 mm diameter outlet pipe from Taylor s Slough. A rough estimate of the capacity of the 750 mm diameter CSP outlet pipe from Taylor s Slough yielded a flow capacity less than 1 m 3 /s far below the 200-year flood estimate of 14 m 3 /s for Kimberley Creek (without peak attenuation in Taylor s Slough). Figure 4 illustrates a proposed route for the Taylor Slough Channel Outlet to Mark Creek. Further discussion with the City of Kimberley and landowners as well as detailed land survey and hydraulic modeling / engineering design would be required. 6. MEADOWBROOK WATERWORKS DISTRICT'S WATER SUPPLY Kimberley Creek flows out of the Meadowbrook Waterworks District's water supply dam through the Morrison Subdivision (locally known as Morrison Sub) and under Pearson Road to the confluence with Lois Creek. A cursory review of the dam upstream revealed that there is no evident overflow spillway, no floating debris boom and apparent shoreline erosion among other concerns. The power pole is leaning and there are unknown materials left on the dam crest. It is understood that the City of Kimberley is not responsible for the dam however the City of Kimberley could conceivably be impacted downstream during a dam failure. 7. MORRISON SUBDIVISION The portion of Kimberley Creek that flows through Morrison Sub has been historically channelized and straightened with numerous driveway culverts. Morrison Sub is located PAGE 5 OF 10

6 within a valley which forms the floodplain of Kimberley Creek with an apparent high water table. Since there are no existing properly designed flood mitigation works in the subdivision therefore during flood events it is understood that the existing main channel overflows and spreads out across the relatively flat floodplain; inundating land, houses and outbuildings. The existing high water table at the valley bottom would tend to worsen the situation with the lack of significant ground infiltration during flooding. It was observed that residents are unilaterally preparing to install rock flood walls and fill within the floodplain which may tend to cause third party transfer of flood and erosion risk. Works in and about a stream (including culvert replacements and armouring) would typically require a Section 9 Water Act permit from the Province, in consultation with the City of Kimberley. Downstream of the subdivision there are multiple culverts at different invert elevations under Pearson Road which could tend to collect debris and cause a backwater upstream during flood events. 8. CONCLUSIONS AND RECOMMENDATIONS 1. The Kimberley Creek watershed is an actively logged watershed which in recent years has had significant mountain pine beetle infestation. The pine tree beetle-kill may tend to increase the annual water yield in the watershed for decades to come. Large scale removal of trees from the Lois and Kimberley Creek watersheds may also increase peak runoff in Kimberley Creek. Furthermore, due to the chronic flooding issues on lower Kimberley Creek within the Morrison Sub and at the upstream end of the Kimberley Creek intake works, any further increases in hydrological inputs may exacerbate the flooding downstream. It is recommended that a comprehensive reforestation of logged areas and beetle-kill salvaged areas be undertaken in the Lois Creek and Kimberley Creek watersheds. 2. Both Lois Creek and Kimberley Creek are flashy mountain creeks with significant logging activity in their upper watersheds which would tend to increase the peak runoff. Major flooding is expected to occur during spring storms coupled with snowmelt. The 2, 5, 10, 20, 50, 100, and 200-year floods on Lois Creek and Kimberley Creek have been estimated and are shown in Table Recent flow stage data recording for Lois Creek, Kimberley Creek and downstream of Lois Creek and Kimberley Creek confluence should continue for at least 10 years and a stage-discharge model should be developed for flow determination and analysis. PAGE 6 OF 10

7 4. A cursory review of the capacity of the Kimberley Creek intake for the diversion to a storm sewer through to Mark Creek indicates that it is undersized and not capable of passing the 200-year flood on Kimberley Creek (even with the Lois Creek flows diverted). The acceptable Provincial standard for flood control is the 200-year flood. Any debris blocking the intake culvert entrance would further reduce the hydraulic capacity of the intake. Upgrading of the existing storm sewer through the City of Kimberley would appear to be problematic and costly. 5. A cursory review of the Mark Creek flume indicated that the flume is past its service life and any additional diversion of water into the flume would not be advisable. Therefore consideration should be given to retiring the Kimberley Creek intake and replacing it with an open channel diversion around the flume via Taylor s Slough and the proposed Taylor Slough Outlet Channel into Mark Creek downstream of the flume. 6. A reconnaissance of a possible open channel route with culverts under roads was carried out as shown in Figure 1. The route would take advantage of the peak flow attenuation in Taylor s Slough and avoiding the Mark Creek flume. Further discussion with the City of Kimberley and landowners as well as feasibility study carried out including a detailed land survey and hydraulic modeling / engineering design would be required. A rough estimate of the capacity of the 750 mm diameter CSP outlet pipe from Taylor s Slough yielded a flow capacity less than 1m 3 /s far below the 200-year flood estimate of 14 m 3 /s for Kimberley Creek (without peak attenuation in Taylor s Slough), therefore daylighting of the pipeline into an open channel should be considered to accommodate the 200-year flood with adequate freeboard. A possible route for the proposed Taylor Slough Outlet Channel is shown in Figure Since Taylor s Slough was apparently used as a tailings pond in the past it is recommended that sediment sampling be carried out in the slough, before a final decision is made to re-route the water from Kimberley and Lois Creek into it. In addition, a reservoir routing analysis should be carried out to determine the attenuation in Taylor s Slough. 8. The Meadowbrook Water District s water supply dam is located just upstream of Morrison subdivision. A cursory review of the dam revealed there is no overflow spillway, floating debris boom and apparent shoreline erosion was noted. The power pole is leaning and there are unknown materials left on the dam crest. This small dam should be inspected by a Professional Engineer and the dam inspection report submitted to the City of Kimberley. 9. The Morrison subdivision was also reviewed and it is evident that the flat land in the narrow valley is subject to periodic flooding from Kimberley Creek. It is understood that the existing channel overflows and spreads out across the relatively flat floodplain inundating land, houses and outbuildings. There are no existing properly engineered PAGE 7 OF 10

8 flood mitigation works in the Morrison subdivision. It was observed that some flood mitigation works have been constructed on individual properties along with earth fill within the floodplain which may tend to cause third party transfer of flood and erosion risk. 10. It is recommended that a Professional Engineer qualified in flood control engineering carry out a flood transfer of risk assessment and establish Flood Construction Levels, building setbacks and flood control mitigation works for the Morrison subdivision. The recommended Flood Construction Levels should be noted on the land titles of affected properties pursuant to Section 219 of the Land Title Act. The City of Kimberley should establish specific development regulations for the Morrison subdivision to reduce the risk of injury, loss of life and property damage due to flooding. 11. The Morrison Sub also appears to have a high water table especially during wet periods reducing potential infiltration into the ground during wet periods and exacerbating the flooding situation. It is recommended that a Professional Engineer qualified in groundwater review the need for instrumentation and analysis of the local groundwater regime. 12. The Kimberley Creek reach through Morrison Sub appears to have been channelized, straightened and with numerous culverts. The culverts do not have the capacity to pass the 2-year flood in Kimberley Creek (headwater to diameter ratio of 1). A sanitary sewer and domestic waterline were observed in the field to be installed within a portion of Kimberley Creek (within the Morrison subdivision); therefore consideration should be given to separate the alignments of the sanitary sewer / domestic waterline from the Kimberley Creek channel 13. The City should inform residents not to block culvert openings in Kimberley Creek and inform them that unauthorized flood mitigation works in or around the creek could result transfer of flood risk possibly resulting in liability if other third party buildings and / or properties are affected. 14. The multiple culverts with various inlet invert elevations under Pearson Road could cause a backwater condition during a flood event. It is recommended that the culverts should be replaced with one large culvert with a trash rack based on hydraulic modeling. The design of this culvert should be carried out by a qualified Professional Engineer. 15. Riparian setback zones for both Lois Creek and Kimberley Creek should be established within which a proper functioning channel should be constructed with ponds, weirs and channels by a qualified multi-disciplinary team using hydraulic modeling with input from the recently carried out Properly Functioning Condition Assessment in PAGE 8 OF 10

9 16. Floodplain mapping for the 200-year flood level plus freeboard should be undertaken for Morrison Sub including Flood Construction Levels for all habitable structures. 4. CONCLUSIONS AND RECOMMENDATIONS This report provides a hydrological review of Lois Creek and Kimberley Creek. I trust that this meets your present needs. Prepared by: Original Signed and Sealed Issued for Use, February 6, 2012 Brian LaCas, P.Eng., Senior Hydrotechnical Engineer LaCas Consultants Inc. This report: Lois Creek and Kimberley Creek Hydrological Review Issued for Use, February 6, 2012; by LaCas Consultants Inc. (the document); supersedes all previous LaCas Consultants Inc. s documents dealing with Lois Creek and Kimberley Creek. This is document is not meant to be a Flood Construction Level report. As mutual protection to the Client, the public and LaCas Consultants Inc., this document, its drawings, figures, and appendices, are submitted for the exclusive use of the Client for this project only and no other project. No person, other than the Client, is authorized to use this document or reproduce this document in whole or in part in hardcopy or electronically without the express written permission of LaCas Consultants Inc with the exception of Aqua-Tex Scientific Consulting Ltd., the City of Kimberley who are each authorized only to review this document for the purposes of this project only. This report does not include future climate change factors. LaCas Consultants Inc. specifically disclaims any responsibility for losses or damages incurred through the use of this document for any purpose other than for this project. In order to properly understand the suggestions, recommendations and opinions expressed in this document, reference must be made to the whole document. LaCas Consultants Inc. will not be responsible for use by any party of portions of this document without reference to the whole document. PAGE 9 OF 10

10 When LaCas Consultants Inc. submits both electronic file and hardcopies of this document, including drawings and other documents and deliverables (LaCas Consultants Inc. s instruments of professional service), only the signed and sealed hard copy versions shall be considered final and legally binding. Such hard copy versions shall be the original documents of record and working purposes and, in the event of a dispute or discrepancy, shall govern over the electronic versions. The original hard copy sealed and signed version archived by LaCas Consultants Inc. shall be deemed to be the overall original for the project. This document, and all previous reports, calculations, computer modeling, files, notes, drawings, plans, designs, techniques, technologies, methods, concepts, water surface profile data input / output, inventions, specifications and data associated with the project, is the intellectual property of LaCas Consultants Inc., and LaCas Consultants Inc. holds the copyright in all such intellectual property. This document represents LaCas Consultants Inc. s best professional judgment based on the information available at the time of its completion and as appropriate for the project scope of work. Services performed in developing the content of this document have been conducted in a manner consistent with that level and skill ordinarily exercised by members of the engineering profession currently practising under similar conditions. LaCas Consultants Inc. provides no warranty, express or implied, with respect to its work for this project or this document. Use of this document is subject to LaCas Consultants Inc. s Standard Terms and Conditions. LaCas Consultants Inc. does not take any responsibility for the work carried out by any third party on the project. PAGE 10 OF 10

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