FLOOD06541 - Laserfiche WebLink

Home Browse Search

. . John W. Rold Page 5. July 23, 1973 3) Active 1ands1iding on east side of Carbonate Creek. Our original report on the Marble area depicted some of the larger areas of active sliding east of Carbonate Creek and discussed the general problem which is caused by the dip of bedding and joint planes of the bedrock and rapid downcutting by Carbonate Creek. More detailed field study reported by Robinson and Associates in November of 1972 showed active sliding along a half mile or more on the east side of the creek. At some locations they mapped open cracks indicating ongoing activity of the slide masses. During the th~rd week of May, 1973, we started receiving calls from people in and around Marble informing us of active sliding of a large slab toward Carbon- ate Creek. There was concern that the trees and rock debris might temporarily dam the creek and together with the additional sediment cause a serious water or mud flood in the town of Marble. Mr. Ro1d of our office suggested that the slide be put under surveillance and so residents installed a crude but effective ex- tensometer to indicate changes of distance between points on opposite sides of the main slide fissure. the The area of concern was located just downstream from/effluent line that runs from the provisional sewage treatment plant location to Carbonate Creek. The very ac- tive slide extended approximately a hundred yards downstream and the main fissure was about 100 feet east of the stream channel and was about 20 feet back of the steep stream bank. The fissure had opened up from one foot to as much as four or five feet and live trees as well as broken shale bedrock had caved into the active stream channel. When I first checked the "strain gauge" it hadn't moved for more than a week. Closer inspection of the surrounding area indicated that very recent movement ranging from a few inches to as much as a foot had taken place over a much more extensive area back of the main feature and for a greater distance down- stream. There were two hard showers on the second day I was 1n the Marble area and on the fo11~wing day (June 29, 1973) I noticed from the' opposite side of the canyon that several additional trees had fallen into the creek from the slide. When I checked the slide at 2:00 p.m. it had moved nine inches on the reference cord and several feet at a point farther upstream. A considerable amount of new broken shale and large live trees had caved into the stream channel since the previous day. Evaluation There has been considerable discussion and controversy concerning the history of sliding in this area, the possible role of diverted surface water on the activity of the slides, and what if anything can be done to alleviate any threat that such sliding might have on downstream areas. Concerning the first que~tion the geologic evidence is overwhelming that this is a natural and essentially continuous process that extends well past man's tenure in the area. Tilted and bent trees of consid- erable age and landslide scarps of varying ages confirm this, and geologic reports covering the time from 1966 to the present document current activity. To evaluate the possible influence of diverted surface water on slide activity I tried to determine existing as well as natural drainage of the up~ope area. There