Landslide Hazard Zonation Completed Projects
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Landslide Hazard Zonation Completed Projects 
Landslide Hazard Zonation 

Landslide Hazard Zonation Completed ProjecTS

The purpose of these products is to assist foresters and land managers in pre identifying unstable slopes. These products are to be used as a screening tool to guide and assist field personnel. There will be instances where a slope is more or less stable than identified. In every instance, the actual ground conditions are to dictate the course of action. Department employee field verification of hazard and potential for delivery is still required before an application may be classified IV S (or the landowner may opt to avoid conducting a forest practice on that landform).

These information products were created to supplement the existing unstable slopes rules, not to replace them. All of the current unstable slopes rules still apply. (WAC 222-16-050(1)(d), (1)(e), and (1)(g), e.g., inner gorges, bedrock hollows, etc.) In some watersheds, analysts were able to include rule identified unstable slopes as part of the assessment.

The information developed by the Landslide Hazard Zonation (LHZ) project consists of: a map of landslides, a map of landslide hazard areas (also known as mass wasting map units), and a report detailing the landslide hazard findings for that watershed administrative unit. As each watershed is completed, the information is available to the public through the LHZ completed Projects website and the landslide inventory and hazard zone GIS data is available at the Forest Practices GIS Spatial Data Sets page.

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LHZ Completed WAus  (a - m)Date Completed
Bacon Creek (3,670KB ZIP)06/15/2007
Bingin Major Creek (7,040KB ZIP)05/31/2007
Cabin Creek (5,350KB ZIP)10/14/2005
Calawah Lower (6,110KB ZIP)02/08/2005
Canyon Creek NW (7,080KB ZIP)12/01/2006
Chehalis Sloughs (9,220KB ZIP)02/29/2008
Clallam River (5,030KB ZIP)12/13/2007
Cle Elum (8,710KB ZIP)11/08/2005
Clear Warm SL Block (2,080KB ZIP)11/20/2006
Clear Dan Lime (12,100KB ZIP)08/16/2004
Clearwater Middlewt (13,700KB ZIP)09/15/2004
Deer Creek NW (18,600KB ZIP)06/29/2004
Dickey EW (9,450KB ZIP)09/15/2004
Elizabeth Creek (3,625KB ZIP)06/12/2009
Finney Miller (8,743KB ZIP)10/12/2007
French Boulder (6,990KB ZIP)08/25/2005
Garrard Creek (7,914KB ZIP)03/15/2008
Grays Bay (15,300KB ZIP)11/09/2006
Great Bend (8,810KB ZIP)06/29/2007
Howard Hansen (14,400KB ZIP)01/05/2004
Humptulips EW (12,400KB ZIP)12/20/2004 
Jackman Corkindale (7,427KB ZIP)10/12/2007
Kachess (10,200KB ZIP)12/13/2005
Kalaloch (6,080KB ZIP)11/03/2006
Mashel (10,300KB ZIP)12/21/2004
Mason Hammersley (22,400KB ZIP)08/09/2007
Middle Cascade (254KB PDF)08/27/2004
Middle Hoh (7,600KB ZIP)08/17/2004
Mud Mountain (12,100KB ZIP)01/26/2007


LHZ Completed WAus  (N - Z)Date Completed
Naselle Headwaters (12,874KB ZIP)06/19/2009
Naselle Lower (15,300KB ZIP)08/27/2004
Newaukum UNF (9,810KB ZIP)09/15/2004
Newaukum USF (10,900KB ZIP)09/15/2004
Nookachamps (6,320KB ZIP)08/16/2004
Ohop (7,100KB ZIP)08/16/2004
Onion Creek (7,510KB ZIP)08/17/2004
Ozette Lake (7,400KB ZIP)02/29/2008
Powell Creek (4,590KB ZIP)09/15/2004
Queets (9,330KB ZIP)06/19/2006
Quinault (7,840KB ZIP)08/16/2004
Racehorse Creek (4,680KB ZIP)10/06/2006
Raging River (4,040KB ZIP)08/31/2004
Sauk Prairie Rinker (11,500KB ZIP)07/14/2006
Silverton (7,220KB ZIP)07/20/2006
Sinlahekin (7,380KB ZIP)03/29/2005
Siouxon Statelands (10,600KB ZIP)01/13/2006
Skamokawa (14,700KB ZIP)01/16/2007
Smay Creek (6,630KB ZIP)12/20/2004
South Prairie (8,500KB ZIP)02/05/2005
Spada Lake (10,200KB ZIP)04/25/2006
Sultan River (7,200KB ZIP)08/15/2005
Tahuya Statelands (7,590KB ZIP)08/15/2005
Tanwax (7,550KB ZIP)08/27/2004
Teanaway WF (5,800KB ZIP)08/14/2005
Tiger Summit (9,680KB ZIP)12/11/2007
Toats Coulee SF (13,700KB ZIP)03/29/2005
West Branch (8,450KB ZIP)09/17/2004
Whitesalmon Buck Ck (6,030KB ZIP)12/15/2006
Wishkah Lower (2,844KB ZIP)06/05/2009


The approach for regulating forest practices on unstable slopes developed by the authors of the Forests and Fish Report (FFR) has several elements, one of which is the Landslide Hazard Zonation project. The goal of the Landslide Hazard Zonation project (LHZ) is to create an improved screening tool by better mapping and describing potentially unstable slope areas. The purpose is to minimize, to the greatest extent possible, the error of omission in the identification of unstable landforms during the forest practices permitting process.

Where LHZ maps are not available, the next best available screening tool should be used in the following order:   
   1. Mass wasting map units from watershed analysis
   2. Regional unstable landform map combined with SLPSTB data (DNR GIS screen)
   3. SLPSTB data (currently available for the west side)
   4. Soil survey

LHZ mapping is done by applying the watershed analysis mass wasting module methodology (revised for this purpose) to forested Watershed Administrative Units (WAUs) in the state that are subject to Forest Practices Rules (i.e., State and private timber lands); are not urban; and those WAUs where no watershed analysis has yet been completed. Priority was identified for watersheds on the basis of previous work available. Priority 1 watersheds were defined as those that have had a watershed analysis nearly completed in them. Priority 2 watersheds have a mass wasting assessment begun in them, and Priority 3 watersheds had little to no previous studies done in them.

Prescriptions and the LHZ project
In some WAUs where a watershed analysis was started but not completed, the analysis includes draft prescriptions. Completion of the LHZ project does not finalize the watershed analysis prescriptions. In those instances, when the prescriptions make sense on the ground, it is at the forester’s discretion to use the draft prescriptions as conditioning language during the application process.

Completing a Watershed Analysis and the LHZ project
In some watersheds, the landowner may desire to complete the watershed analysis after the LHZ team has done their study of the watershed. It is appropriate to include the results and findings from the LHZ project (including map products) into the completed analysis, prior to submission of the watershed analysis document to SEPA. If the results and findings are not included, then the watershed analysis should not be allowed to enter into the SEPA process, because more recent information has been brought forward that improves the original product.

FPARS-Resource Maps
In the future, the mass wasting units (AKA: hazard zones) will be placed on the Forest Practices Application Review System (FPARS) Resource Map, as one of the ‘clickable’ layers. The DNR is currently compiling these data and will make it available as soon as possible. At present, we do not have an estimated date of arrival for its implementation on FPARS.

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Leslie Lingley
Forest Practices Science Team Lead


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