Geologic Hazard Reports are sometimes required by county planning or building departments, however, they are not always required and it is important to realize why. The "Geologic Hazard Area" adopted by Coos and Curry Counties typically   includes two general areas: 

·         1) a strip of land along the coast (of variable width) including beaches, dunes and seacliffs

·         2) hillslope areas categorized in a regional study as having "slump earthflow" topography in county wide studies by the Oregon Department of Geology and Mineral Industries (DOGAMI) in the mid-1970's.

·         Areas of steep slope identified by DOGAMI as having a potential risk to be impacted by Rapidly Moving Landslides (RML).

Many hillslope areas within Coos and Curry counties which are not classified as having slump-earthflow topography or are particularly steep have landslide or soil-related hazards. In fact, two particularly susceptible areas to landsliding in Curry County which have been subdivided for residential development are not within the Curry County's geologic hazard area because they were not classified as having slump-earthflow topography in a 1976 county-wide DOGAMI study. These include areas adjacent to part of  Jerry's Flat Road near Gold Beach and the South Bank Chetco River Road several miles upriver from Brookings. Homes in both areas have been damaged by natural or grading related landslides and some lots are considered economically not feasible for development.  

                                                         
Why is this?

The county wide studies, done in the mid-1970's and were reconnaissance in nature. The determination of slump-earthflow topography was based on examination of aerial photographs and topographic maps. The findings of the study are shown on a topographic map with a scale of 1 inch = 1 mile and the minimum area delineated is 20 acres. (insert Scanned DOGAMI map here). The report for Curry County actually states on their map legend that landslide hazards exist on all slopes greater than 30% but, for various geo-political and economic reasons, these areas were not included in the Geologic Hazard Area adopted by Curry County in the mid-1980's. 

Settlement and landsliding of fills related to improper grading of hillslope lots has probably caused more damage to homes than natural landslides have in this area. This is because there are very few controls on ot grading within the rural portions of southwest Oregon. Fills are rarely appropriately compacted, they are often too steep, and typically contain woody debris. Ground surfaces beneath the fills often were not cleared of topsoil, limbs and even stumps before the fill was "sidecast" or pushed over them by the bulldozer, particularly on the sites that were "roughed in" in the 1970's and 1980's. Many building sites used to be old log landings or wide spots on logging roads and were never intended to have structures built on them. Cutslopes are often constructed too steep for long term stability and can either erode or fail. Damage related to cutslope failure and erosion is more common on driveways and roads than on building pads