July 21, 2018

Transcription

1 July 21, 2018 A Non-Profit (501C3) Tax Deductible Group, Dedicated to Advocacy of Good Land & Water Stewardship BRIEFING REPORT ON HYDROLOGIC-GEOMORPHIC CHARACTERISTICS OF THE PROPOSED HANTWICK TRAIL-MICHIGAN TROTTER WA DNR PROPOSED TIMBER SALE & INCLUDING FIELD RECONNISSANCE INTRODUCTION: There are landslide effects/impacts and severe erosion/sedimentation risks associated with logging on steep unstable hillsides regardless of the type of harvest configuration and methods used. After the disastrous logging that triggered the large slide at Oso, WA. ---thorough site evaluation, risk analysis, caution, and prudence is a policy to be followed on all DNR timber sales. In some cases, level of risk and other long-term resource values may indicate that it is not prudent from a balanced total resource value perspective to conduct logging on the proposed sale site. LOCATION: The proposed project is located in Clark County, WA about 9.7 miles east of Hwy 503 up Sunset Falls Road along the East Fork Lewis River, on the south side of the river off Hantwick Road and on the left just past the scenic rail road tracks that go from Vancouver to Chelatchie Prairie. The area is part of the Lucia Falls Park complex. There is also a small stream that crosses the west end of the site. The WA Dept. of Natural Resources (DNR) is proposing a logging sale on the hillside just above the edge of the Hantwick Trail which runs along the bottom of the proposed sale area. 1

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3 An aerial photo from the DNR with their proposed timber sale overlain on it is shown in Figure-3 CHARACTERISTICS OF THE PROPOSED LOGGING SITE: The area proposed for logging is on a steep north facing relatively steep slope which ranges from 30% to 60% developed from USGS Quad Map and NRCS (Natural Resource Conservation Service) data and information sources. The elevation contour lines on both the USGS Quad Map and the DNR annotated air photo of the timber sale (Figure-3) also visually show the closeness of the contour lines, indicating that part of the area is on a steep slope. 3

4 Analysis of LIDAR (Light Detection And Ranging) images show the bare ground surface characteristics of the north facing slope where the timber sale is proposed. In the Figure-4 LIDAR image, one can see within the red colored circle, the railroad tracks, the Hantwick Trail parking lot and the trail itself at the bottom of the north facing side of the ridge. The timber sale is located inside the red circle on the north facing slope ridge and ridge top. Note the small stream channel path that flows through the west end of the area and into the East Fork Lewis River. 4

5 GEOLOGY & LANDSLIDE/SLUMP AREA PROPERTIES: The 2006 USGS geologic map of the Yacolt Quadrangle, Clark County by R. C. Evarts showed five geologic formations associated with the proposed logging site. They are QT, QTd2, Tvs, and Tbem. Their locations within and around the proposed logging site are shown in Figure-5 inside the red circle. 5

6 Brief Description of Geologic Formations. The Qt geologic map unit is located directly in the steep north facing slope of the proposed timber sale. Described as talus deposits unsorted accumulations of angular bedrock blocks in East Fork Lewis River Valley. Chiefly rock fall and rock avalanche deposits. The Qtd2 geologic map unit is located at the base of the slope and below the Hantwick Trail. Described as terrace deposits forming terrace along the south side of East Fork Lewis River upstream from Lucia Falls. It is made up of poorly sorted boulder cobble gravel and sand. The Qls geologic map unit is associated with landslides on the east and west end of the area as well across the East Fork Lewis River on north side of the river. Described as landslide deposits of diamiatons of angular bedrock and (or) surficial material transported down slope in mass. Chiefly deep seated semi-coherent slumps and internally disrupted rock slide, earthflow, and debris-flow deposits The Tvs geologic map unit is a narrow sliver along the bottom of the slope at the eastern end of the timber sale area. Described as heavily weathered volcanic clastic sedimentary rocks. The Tbem geologic map unit occupies much of the back or south side of the ridge on the other side of the proposed timber sale area. Described as basaltic andesite of Elkhorn Mountain (Oligocine) tholiitic basalt flows and breccia. Landslide data and mapping specific to the proposed timber sale area was also identified in the Washington Geologic Information Portal as illustrated in Figure-6. For purposes of comparison, the red circle area in Figure-5 and Figure-6 are basically the same areas of Hantwick Trail & the proposed DNR timber sale. Their Geologic Hazard Maps include, Shallow Landslide Hazard Forecast Mapping and Landslides & Landforms which are derived from mapped landslides but also states that The absence of a mapped landslide does not indicate the absence of a landslide hazard. 6

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8 Other indicators of land slide, slumping, or creep issues are sometimes indicated by vegetation disturbance manifested in the form of trees on a slope leaning at odd angles. Doug Fir on slump areas have been known to actually slowly grow back to a vertical angle from a curved butt or base. Soils types and characteristics are good indicators of potential stability hazards and erosion risks if the area is disturbed by various types of activities. Soils data and information was also available thru the United States Dept. of Agriculture Natural Resources Conservation Service (NRCS), Web Soil Survey service. The soils identified and mapped include the following, starting at the bottom of the proposed timber sale cut slope on up to the ridge top ---refer to Figure-8 Soils Map: 8

9 Soil Types Mapped in and around the proposed timber sale area. YaA Yacolt Loam, 0 to 3 percent slope. Occupies sliver of land at bottom of slope between trail and rail road track OmF Olympic stony clay loam, 30 to 60 percent slope. Occupies the major portion of the proposed slope logging area between the Hantwick Trail and almost to the ridgetop to the south. Rk Rock land, slope 65 to 90 percent. Occupies the ridgetop at the top of the slope. NOTE: The majority of the soil that is in the proposed north slope facing logging area is identified as OmF and is classified as Poorly Suited or Severe erosion hazard --- see Figures 9 & 10 Maps, Legends, & Tables series. 9

10 Characteristics and Use Ratings of soil groups are shown in maps and tables. The following soils information is taken directly from the soils report generated by the NRCS Web Soil Survey. 10

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12 Figure-9 Series: NRCS Log Landing Suitability Map, Legend, & Suitability Table - Michigan Trotter Proposed Logging Area. Figure-9A Soils Map Of Proposed Logging Area 12

13 Figure-9B Soil Type Legend For Soil Map Shown In Figure 9A 13

14 Figure-9C Soil Suitability Table For Soil Map Shown In Figure 9A 14

15 Figure-10: Series NRCS Erosion Hazard (Off-Road, Off Trail), Legend, & Suitability Table For Michigan Trotter Proposed Logging Area. Figure-10A Series NRCS Erosion Hazard (Off-Road, Off Trail) Map 15

16 Figure-10B Map Legend For Erosion Hazard Map (Off-Road, Off Trail) 16

17 Figure-10C Map Table For Erosion Hazard Map (Off-Road, Off Trail) 17

18 Figure-11 Series Valley Cross Section & Line Of Sight Analysis Figure-11A North/South Cross-section Of East Fork Valley Cutting Thru Proposed Timber Sale Area Figure 11A indicates that from the north side of the East Fork Lewis River along and above the Lucia Falls/Sunset Falls road one can see the proposed area to be logged. The view conditions on the south side of the river at the railroad tracks or at the Hantwick Trail are quite different depending on a number of factors. 18

19 Figure-11B South Side Slope by East Fork- North/South Cross-section Of East Fork Valley Thru Proposed Timber Sale Area The line with the two arrow points show where the cross-section was taken off of a USGS Quad. Map and the cross-section image and basic data that resulted from it. The cross-section runs up the slope starting at the bottom of the north facing slope near where the Hantwick Trail is located and proceeds up the slope to the ridgetop. Starting elevation is at 408 ft. and ends on the ridge above at 920 ft. The image capture (small image insert) distorts the scales visually and does not clearly show how much steeper the upper half of the slope is, but looking closely at the 20 ft. contour lines on the USGS map shows the difference in contour line spacing and is verified by field checking. 19

20 Figure-11C Expanded View Of South Side Slope by East Fork- North/South Cross-section Of East Fork Valley Thru Proposed Timber Sale Area Figure 11C is a more detailed cross-section view of the slope at the proposed logging site. Again, note that the scaling of the diagram does not visually clearly reflect the steeper upper half of the slope. A line of site upslope from the rail road tracks (408 ft. to 913 ft.) or the trail would be affected by the density of trees left under various logging systems proposed. Even so, leaving an edge upside of the trail of 60 ft. to 100 ft. tall trees, unless very dense together, would not hide the proposed logging from some level of view at the trail. 20

21 Figure-11D Expanded View Of Upper Steep Section Of Proposed Logging Slope On South Side Of East Fork- North to South Cross-section Taken Thru Proposed Timber Sale Area This image of the upper slope area cross-section of the proposed timber sale shows a very steep 74% slope. Again, because of software scaling of the USGS Quad the data is derived from, the bottom scale of distance and the visual effect of the vertical scale differences, need to be recognized when reviewing the image ----focus should be on the data at the bottom of the image. It is the 285 ft. height change over the 378 ft. horizontal distance that equates to the steep 74% slope section on the proposed timber sale. 21

22 JULY 14 TH, 2018 FIELD RECONNISSANCE OF PROPOSED HANTWICK TRAIL LOGGING AREA: Saturday July 14, I a field reconnaissance of the Hantwick Trail-Michigan Trotter proposed WA DNR logging area by Friends of the East Fork Lewis River, Richard Dyrland-Hydrologist. FIELD RECONNISSANCE AREA COVERAGE: The intention was to walk up the north/south dividing ridge of the proposed logging area, then at about in the middle, proceed down the slope, cross the trail, and continue on north to the railroad tracks. I started my field reconnaissance by walking up along the east side of the small creek that was located just past the trail bridge. I soon encountered what looked like a narrow trail that people had occasionally used, or was used by DNR people to reach parts of the proposed logging area. I follow it up the hill towards the dividing ridge top and found a DNR sale/reference stake or boundary marker. Walking east along the upper area of the logging project site I began to observe the ground and vegetative characteristics and particularly the conditions of trees (softwoods and Doug. Fir) on the area. Photographs were also taken to help document anything that I thought would be of interest to our concerns as well as basic area conditions. About 40 of the many photos taken appear to be of particular interest. Going down the steep slope I encountered what appears to be a slip or slump face with a 10 ft. or 12 ft. of drop where in the past the ground had separated and slid down hill. This is not inconsistent with the geologic and soils data and information identified identifying potential site instability, and discussed in the FOEF Briefing paper. 22

23 Photo of Apparent Slip or Slump Face Near Top of Proposed Logging Sale Area 23

24 Photo of Leaning Doug. Fir Trees on Slope Also in this area there were both Doug. Fir and hardwoods that were leaning which indicates possible soil creep and surface instability consistent with geologic and soils data for the site. Examples of these are documented with several photos. It is of interest to know that in locating powerline routes, one of the ways that Bonneville Power identifies landslide or unstable slope conditions when soils and geology maps may not be up-to-date, is to look for leaning trees. Particularly Doug. Fir that have a curved stem at the base of the tree indicating it is on unstable ground or subject to ground creep and is trying to grow straight upward. Their experience indicates that for hardwoods, they generally don t have a growth pattern that tries to correct this but continue to grow at a downslope angle. I observed some Doug. Fir on the site that appeared to have made some growth adjustment for slope creep, as well as seeing Fir trees that appeared to be tilted downslope. I took pictures to capture some of these apparent Doug. Fir tree conditions located at various places on the proposed logging area. 24

25 Just below the lower boundary of the proposed logging site and above the trail, there are many hardwoods that have a substantial amount of downhill tilt and some do hang over the blacktop trail. Photo of Lower Sale Boundary Marker From the trail the sale area could be seen thru the trees as well as the ridgetop. Photographs were taken to document this. I proceeded north off the trail and on across the vegetated area that separates the trail from the railroad tracks. From the tracks, one again can see the proposed logging area as well as the ridgetop, and photographs were taken to document this. There was also a DNR stake near the railroad track with markings on it. This was also photographed. 25

26 Photo of Rail Road Tracks Including WA DNR Stake CONCLUSIONS: (THESE CONCLUSIONS ARE BASED ON EVALUATION OF BOTH DATA & INFORMATION SEARCHES, THE FIELD SITE RECONNISSANCE, AND THE DISK-1 WA DNR FOIA INFORMATION. The field reconnaissance of the area, the line of site view factors along with the data and information on hydro-geomorphic slump/slide and erosion risk levels of the soils, geologic and overall vegetated slope conditions previously discussed, should be intensively considered in determining whether it is still prudent to move ahead with this proposed WA DNR sale ---as it now exists. The information on the DNR FOI Disk indicated in one memo that they would still have to cut leaning trees below the logging boundary after the area above was logged. Other logging configurations with a lower slope stability & erosion risk as well as visual impact still need to be considered. 26

27 CONCLUSIONS CONTINUED: And just as important, Clark County should renew the effort to look deeper and farther to find ways of obtaining direct funding or grants to purchase the site from the WA DNR. There are a number of regional and national as well a private or non-profit sources such as Nature Conservancy who should be contacted. In the end, these lands managed by the WA DNR but are owned by the citizens of Washington and have both social and land stewardship as well as economic value. Some of these lands, including the Hantwick Trail area, are part of the very exceptional Lucia Falls/Moulton Falls Clark County Recreation/Parks complex, and they are identified as a type of classification known as an IRREPLACEABLE ASSET. The economic value as well as the social value of irreplaceable natural/environmental assets is now internationally recognized and must be included in any decision that affects the character of a given parcel of land or land area (New Economics Foundation, Valuing the Environment in Economic Terms). There are numerous national and international studies that document this in detail, and many can be found by a Google search. Prepared by Friends of the East Fork Lewis River, Richard Dyrland, Retired Federal Regional Hydrologist & Natural Resources Policy & Program Analyst Toppacific2@msn.com