Link between loggin landslides debated Jamieson Creek slide focus of controversy an N NOVEMBER and December 1990, the Lower Maintand’s drinking water turned brown for two weeks as intense rainstorms caused wide- spread landslides in North Shere watersheds. By Greg Feiton Contributing Writer Storms caused J5 slides in the two months and the Tollow- ing April. Of these, 29 occurred in unlogged areas and account- ed for 94% of slide debris and six occurred in clearcut areas. Five of the six clearcut slides were small and accounted for 0.5% of the debris. ; The sixth clearcut slide was the Jamieson Creek slide in the Seymour watershed on Nov. 23. This slide is a seminal event in the debate between the Greater Vancouver Regional District (GVRD) and its critics over clearcut logging and road construc- tion in the watersheds. Over a six-year period, (1978-84) intensive logging and road construction was carried out in 16.5% of the entire Jamieson Creek drainage area. The authors of the The Final Watershed Evaluation and Policy Review said that this percent- age was well above the normal 1.5% average for ali watershed lands in this period. The area was logged as part.of a long-term comparative study into the effects of harvesting on water quality and quanti- ty. While Jamieson Creek was managed, no logging or road construction took place in neighboring Elbow Creek. From 1984-1988 Prof. Doug Golding, one of the authors of the final policy review, compared erosion in both regions and found little difference. The slide happened approximately a year after Golding’s study. “Four years is not an adequate period over which a study of . this nature can obtain conclusive results,” said environmental researcher Peter C. Friz in a report this April for the Society Promoting Environmental Conservation (SPEC). “After four years the tree roots are still able to hold the soil together and the slope is still somewhat stable after this time, as it can take as jong as 15 years for tree roots to rot and destabilize the hills- lope.” The authors of the Review also wrote that clearcutting on steep slopes can result in the loss of stability over time because of the decay of tree rovis: “Heavy rain storms in the five- to 15-year post-harvest period ca. lead to slope failure on steep slopes as a result of this diminution in root: strength. Hoa slide reaches a stream, this could cause stream sedimentation.” Mark Wareing of the Western Canada Wilderness Comuaitiee said the Jamieson Creck slide was directly caused by a logging road. “The logging roads are the major source of the sediment that is getting into our reservoirs,” he said. . Based on several studies in the Pacific Northwest, the Review said: “The preponderance of information indicates that road construction and maintenance tend to have a much higher potential impact than harvesting operations.” But according to the GVRD and its consul- tant, Thurber Engineering, road construction and harvesting operations were not responsible for the Jamieson Creek slide. “There are places were there is a strong relation between clearcutting, road building, landslides and production of sedi- ment,” said Thurber consultant Robert Gerath, “however, in our judgment, the watersheds are not one of those places.” Whereas critics charge that the ciearcut con- tributed to soil destabilization, Thurber concluded that it could not say for certain whether the cleazcut above the slide area played any part in it. “According to the report,” said GVRD silviculturalist Brian De Gusseme, “the initiation point was well below the root line. To my best knowledge, I agree with the Thurber Report on the Jamieson Slide ... .” The reputation of Thurber’s expertise also persuades GVRD water manager John Morse that GVRD oper- ations had nothing to do with the slide. “When they say that they cannot detect that the forest management practices ... con- . tribute in any way to soil erosion in the watershed, that’s what we rely on.” Morse said the slide occurred due to soil conditions, specifi- cally related to the area’s glacial (hardpan) foundations: “There is an impervious layer of hardpan that is overlain by 1.5 to2 m NTU-DAYS WHEN TURBIDITY >5 NTU (Thousands) ae A AECS CATA eee g | APILANG WATERSHED Sunday, July 24, 1994 - North Shore News - 3 ‘x ! TURBIDITY, CUMULATIVE ROAD'S BUILT BY YEAR 200 a Bias Turbidity Note: NTU-Days whan turbidity >> NTL is the sum of all dary turbidity teadings over 5 for a year. an (a) = r=) te (QALLVINWND) SUSLEHOIUN = ay o ~~ wo Seocoonsn & a 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Source: GVRD Final Watershed Management Evaluation and Policy Review NEWS yrephics Linda Douglas WATER FROM the Capilano watershed has the highest turbici- ty readings but the GVRD says this graphic shows there is no direct correiation between road construction and incidences of extreme turbidity. | (4.9 to 6.6 ft.) of soil. With intense rainfall, water perks into the ground, reaches that layer and starts to nin on top of (it) under- neath the ground. After a while the muaierial above it liquifies and away it goes.” . But in February 1992 Elaine Golds of the Burke Mountain Naturalists wrote: “The Thurber Report also states ‘in our opin- ion, each of the clearcut slide areas was hydrogeclogically stressed before the areas were harvested ... It seems obvious to me that if we cannot predict or assess the stability of these steep slopes before logging, then we should not risk logging them at all.” This is the third instalment in a special North Shore News series examining sone of the key issues in the debate over Lower Mainland water quality. . . Next Week: The Politics of Logging Slope stability determines logging suitability N 1984, the Greater Vancouver Regional . District (GVRD) adopt- ed the Aqua-Terra Classifi- cation System (ATCS). to determine which water- sheds had sufficient slope stability for logging and road construction opera- tions. By Greg Felton Contributing Writer Taking together a range of fac- tors — including slope angle. veg- etation, geological and soil materi- als, and hydrological properties — the ATCS divided the watersheds into five units: * ATCS 1 (slopes less than 27°); * ATCS 2 (slopes 27°-30°); + ATCS 3 (30°-35°), * ATCS 4 (more than 35°); *ATCS 5 (for high alpine regions). The GVRD terms the lands in ATCS | end 2 and 35% of ATCS 3 to be Forest Management Units (FMUs) and suitable for harvest- ing and road construction. These lands comprise 22,337 ha or 38% of all watershed lands. : (moderate) . - 30-35% . “Sour Cur ann Uncut, NUMBER OF SLIDES INITIATED IN ae -_ (number per 1 000 hectares) ce: GVAD Final Watershed Management Evaluation and Policy Review. IN THIS relation between slope grade, logging and tandslides in Lower Mainland watersheds, the figure of 6.2 ha was at first mistakenly published as 16.2 ha. WaTERSHED AREAS stable areas: 62% on slopes less than or equal to 30° (ATCS [-2) and the rest between slopes of 30° and 35° (ATCS 3). The Jamieson Creek slide occurred within this stable area, Environmentalist Elaine Golds, among others, has insisted that logging operations be restricted to ATCS 1. She said the authors of the final report ignored data that showed the danger of logging in ° ATCS 2. - In a September 1991 press release on behalf of the Burke Mountain Naturalists she wrote: “In the Seymour watershed landslides occurred twice as often on logged vs. unloggéd lands with slopes of 27 to 30 degrees. These important findings appear to have been overlooked by the water committee and largely ignored by the panel in their three-volume final report.” Golds points to an error in the report itself concerning potential SIS est f for landslides in the Seymour ‘| watershed. While the correct data appears in an appendix, she said the text reflects an earlier error that went uncorrected. The text of the report does not include the Seymour watershed The remaining part of ATCS 3 and ATCS 4 and 5 are termed Watershed Reserve Units (WRUs) where forest operations are restricted. These comprise 57.971 ha or (62%) of the watershed. The Final Watershed Manage- ment and Evaluation Report said CALL US: 983-2208 that the risk of slides and surface erusion in ATCS | was “generally not a problem”; in ATCS 2 slides were not # major concern but ero- sion could occur if harvesting and road construction were not carried out properly; and that lands in ATCS 3 were “potentially unsta- ble” and operations there required careful planning. Recognizing that road con- struction and maintenance have a greater effect on water quality than harvesting operations, the report concluded that the GVRDB uses “best management practices” for forest operations to mitigate erosion and sedimentation. Some of these practices include: revegetation of slopes. use of silt fences, sediment traps and bank tapering. It also said the GVRD-planned forest operations are on the more THIS WEEK’S QUESTION: Should the Montroyal connector be built creating a parallel northern route to the Trans- Canada Highway? when stating that land movements tend to be more frequent in har- vested as opposed to unharvested ATCS 3 regions. (The original error had 16,2 slides/1,000 ha instead of See GYRD page 5