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"ln-stream structure" is a human-made structure placed within a stream or river watenvard of the ordinarv high water mark that either causes or has the potential to cause water impoundment. or the diversion, obstruction. or modification of water flow. ln-stream structures may include those for hydroelectric generation. irriqation. water supply, flood control. transportation. utilitv service transmission. fish habitat enhancement. or other purpose. 174.02.470 LandslideHazardAreas. "Landslide hazard areas" are areas potentiallv subject to landslides based on a combination of qeoloqic. toooqraphic. and hvdroloqic factors. Thev include anv areas susceptible because of anv combination of bedrock. soil. slope (gradient). slope aspect. structure. hvdroloolr. or other factors. A slope is delineated by establishing its toe and top and measured by averaqinq the inclination over at least ten (10) feet of vertical relief. Potential landslide hazard areas include but are not limited to the followinq areas: 1. Areas designated as quaternary slumps. earth-flows. mudflows. or landslides on maE published by the U.S. Geolooical Survev or Washinqton State Department of Natural Resources. 2. Areas with all three (3) of the followinq characteristics:a. Slopes steeper than fifteen percent (15%): b. Hillsides intersectinq qeoloqic contacts with a relativelv permeable sediment overlvinq a relativelv impermeable sediment or bedrock: andc. Springs or qroundwater seeoaqe. 3. Areas that have shown movement and/or are underlain or covered bv mass wastaoe debris:4. Slopes that are oarallel or sub-parallel to olanes of weakness (which mav include but not be limited to beddino planes. soft clay layers. ioint systems. and fault planes) in subsurface materials: 5. Slopes havinq qradients steeper than eiohty percent (80%) subject to rock fall during seismic shakino: 6. Areas that show evidence of. or are at risk from snow avalanches; and7. Any area with a slope of forty percent (40%) or steeper and with a vertical relief of ten (10) or more feet except areas composed of competent bedrock.8. Potentiallv unstable slopes resultino from river erosion or undercuttinq.9. Areas that show past slouqhinq or calvino of sediment or rocks resultinq in a steep slope that is poorlv veqetated. 10. Deep-seated landslide areas characterized bv one or more of the followinq features. which mav be evident in aerial imaqes. topoqraphic maps. LiDAR imaqerv or on the oround:a. scalloped ridqe crests at the too of the slope. b. crescent shaped depressions.c. head scarps. d. side scarps.e. ponds or sag areas on mid slopes,f. benches and scaros on mid slope areas,q. hummocky ground. h. linear fractures in the qround. 11. Areas below unstable slooes or that have been identified as landslide hazard areas that could be impacted bv landslide run out. 12. Areas above or adiacent to unstable slopes that could be impacted if the landslide area expands. 17A.02.480 Mine Hazard Areas. 26