From paae & Debris flows along the Squamish Highway in the ‘80s were widely reported with those on M Creek, Charles Creck and Alberta Creek resulting in 12 casualties. The Squamish debris flows prompted local research and the subsequent use of debris basins and channelization works, The district consuirants, Kerr Wood Leidal Associates and EBA Engineering Consult- ants, say lessons learned from these projects can be applied wo the district situation. Debris flows are a form of rapidly moving channelized landslide consisting of 2 mix- ture of sediment, organic debris (boulders, logs, tree roots etc.) and water. Usually they occur on small steep creeks that have abundant sources of debris. Dedris flows are referred to as debris torrents when they have a particularly high organic content, or mudflows when they are dominated by clay, silt 40 creeks siudied for flow From page 1 Restoration work and the construction of a concrete catch basin to contro! future debris floods cost the district approximately $2 million. The effects of that expen- _ diture are still being felt in terms of delays to other cap- ital projects. According to the district's director of engincer’ig Bob West-Sells, there dad been no specifically documented debris flows in developed areas of che district prior to that time. “The 1995 debris flow on Mackay Creek was enough of a wake-up.call chat we took another look at all our creck systems,” West-Sells told the News. More than 40° creeks across the district were stud- ied in the report from Capilano Lake to Indian Arm. “Over half had a degree of risk that was high,” said or sand, Debris fows tend te occur in wer weather but don’t alwaes cvincide with food events. Trigger mechanisms include debris slides (filed logging roads can contribute to these), log jam release, flood surge’, creek bed instability and wet snow avalanclies. Debris flows scour the transportation channel with the croded material contributing to the flow volume and discharge. Creek fans occur when the creck gradiens and channel become too flat to contain the flow. Damage in creek fan areas during debris flows can be severe. Flooding of adjacent areas can occur if the creek channel shifts. Debris flaw frequency is largely controlled by ihe avail- ability of sediment and debris, basin geometry and the severity and uming of weather condi- tons. There are generally two types of debris flow systems: those having an_ infinite amourt of erodible material in West-Sells. “That was a bit of a surprise all right.” Heading the list of creek systems at risk are five that have been prioritized for immediate action. They are: & Mackay Creek; Mosquito Creek, @ Percy/Vapour Creck; ® Shone/Underhill Creck; & Coldwell Creek. All are slated for further detailed studies at $50,000 each. : The studics are intended to produce a plan for “active risk mitigation measures.” At an in-camera mecting Wednesday, council dedicat- “Specializing in Mon’s Hair... for all ages 3 North Park Mens Hair . Hyou have been injured in an auto accident Ca Stephen Anderson 922-8881 SAGER ANDERSON LAWRENCE Barristers & Solicitors HL 235-15th Street, po nee eee nes _ lis THIS.the Man that KP _| Drank all your Xmas wine? é ¢ West Vancouver ~=73 Gy WAESER ECE AYDER Bring in this Ad to receive special Park & Tilford Centre _990-RACK (72 the headwaters. In this case any storm exceeding a critical pre- cipitation threshold can uigger a debris flow; those having a limited amount of debris available. The creek gradually recharges with debris until it becomes suili- cientiv joaded to be triggered by more storm water than the creek can handle. Debris floods are defined as intermediate events between floods and debris flows. Hazard ratings assigned in the report relate to the proba- bility of occurrence on the fol- towing scale: Very High: more than once in 20 years; W High: between once in 20 years and once in 100 years; | Moderate: between once in 100 years and once in 500 years. Potential consequences are subjective assessments of the damage potential to the downstream fan or ercek reach in the event of a debris flow. The ratings range from exten- sive structural through minor ed $50,000 frorn its capital reserve to initiate the studies of the five prioritized creek system and will add the remaining $200,000 to its 2000 capital budget. West-Sells hopes to have the detailed studies complete towards the end of 2000 so that further capital expendi- tures can then be prioritized. He was reluctant to esti- mate the total bill but-sug- Expressions that Last a Lifetime We specialize in custom design Bis VESIGl #2-2435 tharine Dr., Wast Van 922-3014 cwac ianey FACTORY Ses rn ANY O72, CHANGE PACKAGE Formerly Sheit Rapid Lube Lonsdale & 15th N. Vances:ver 985-1050 Rusk is the product of hae- ard and consequence, and ranges from very high to very iow, Risk ratings are provided for both debris fleods and debris flows. A high hazard (high proba- bility and magnitude of event) and a very high consequence (extensive structural damage) equals a very high risk. Including what fas already been spent, the district will robably spend close to 31 mit- ion just to define the order of risk. The overview study con- cludes that: £8 The creck tributaries to Capilano Lake are subject to debris flow hazards but the consequences are low and therefore levels of risk are low. The Mackay Creck main- stem has sufficient debris low risk to warrant specific detailed consideration of mitigative measures. The debris flow risks at upper Mackay Creck have been mitigated by a debris hazards gested that it could “conscr- vatively” be $5 million to $10 million. Said West-Sells, “We’re not saying there will be a debris flow this year or next, but we feel that those creeks are of significant enough risk that we'll move as quickly as possible on them.” $ 49 COMPARE md | | ste Sectces: Satis pice sefa hed frase, triple (aan core futon, scetch-guarked fate? covet, it:s end plses covers. Weis Ruantities last 267 E ist, Wan | FUTON Entrance in fear lane Han~Sat.n-Spnsumtyie-son 984-4504 Vradetn ‘Ingtallatio Drivein: . BL CHANGE Sines 1078 11D. HF Sunday, July 25. 1899 - North Shore News — S ne creeks basi and other measures. Bi Mosquito Creek has a very high risk ansing from a moder- ate debris flow hazard and a verv high debris flow hayard. Existing works partly mitigate this risk. @ The Mount Fromme and East Seymour creeks generally have a low debris flow risk rat- ing, with the exception of a few crecks with moderate or mod- erately high debris flood risks. & The Deep Cove creeks typ- ically have moderate hazard probability and high potenti! consequences. Therefore, the risk is typically moderately high, or higher. @ The Indian Arm creeks typ- ically have a high or very high debris flow hazard rating. Due to the low level of development these hazards do not necessari- ly correspond to an equally high risk cating, but some sig- ifcant risks are identified, A number of other potential creek-related hazards have been identified. ‘These include debris flood hazards at Lynn Creek and Seymour River and potentially unstable esearp- ments dong Lynn Creek and Seymour River. Debris flow risks can be mic- igated by cither passive imea- sures such as land-use planning to avoid the hazard. or active measures such as debris basins to mitigate the risk. Preliminary risk mitigation recommendanons in the report include watershed management actions by the Greater Vancouver Water Districc, Grouse Mountain Resorts, BC Hydro, B.C. Parks, B.C. Highways and others besides the district. Council immediately moved to publicize the report after receiving it Wednesday. The report will be circulated to any groups involved in com- munity planning and is avail- able for viewing at all district libraries as well as ar the munic- ipal hall. Information bulletins will also be posted on the dis- trict Web site . The consultants will make a presentation at a public meet- ing to be held in Sepxember. Lingerie, lovers toys & kama sutra niassage products. We have many of the products featured on Sunday night TV: FSoue Nest Adding spice to your love life Jor 20 years “-J6L East ist St. Ge “N, Vancouver t jen Late: ald There & Fri. Open Sunday 987-1175 Information is power. Consider an investment that’s truly plugged in. . aya Smae : ie asec ea Tap into the power of a wired world. As pagers, fax machines and cell phones become a more essential part of people's daily lives, the drive to develop newer, faster and more efficient technologies intensifies. 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