rOREGON STATE UNIVERS TY LIBRARIES IIIIII 111IIIII1 IIII III 12 0002098016 65458 .8 05 cop .3 FINAL RE PORT (Report on an investigation carried out under Contract Nonr-2771 (04), Project NR 388-062, between the University of Oregon and the Office of Naval Research, U. S. Department of the Navy.) Reproduction in whole or in part is permitted for any purpose of the United States Government. SOME RECENT PHYSICAL CHANGES OF THE OREGON COAST by Samuel N. Dicken assisted by Carl L. Johannessen and Bill Hanneson Department of Geography University of Oregon Eugene, Oregon November 15, 1961 Reprinted in the public interest by the EugeneRegister-Guard and the Lane County Geographical Society,Inc., April, 1976. ACKNOWLEDGEMENTS The subject of coastal changes is of interest to many people living on or near the Oregon coast and, as a result, numerous interviews, only a few of which can be acknowledged, furnished much information not otherwise available. Valuable assistance came from persons concerned professionally with some aspect of coastal change. The staff of the U. S. Army Corps of Engineers, Portland District, was most helpful, especially H. A. Kidby of the Rivers and Harbors Section, Lloyd Ruff of the Geology Section, Mr. Charles Oros of the Photogrammetry Office and Dorothy McKean, Librarian. Mr. E. Olson of the U. S. Coast and Geodetic Survey located copies of old charts and other materials.Ralph Mason of the Oregon State Department of Geology and Mineral Industriescon- tributed notes on Ecola Park and other areas. Robert L. Brown and the staff of the U. S. Soil Conservation Service furnished photographs andspec- ific information on vegetation changes of the dunes.Park Snavely of the U. S. Geological Survey contributed several suggestions and old photographs. The staff of the Oregon State Highway Department, including George Wells, Daniel Gano, and Lloyd Wolfe, aided in many ways. J. W. Johnson and R. L. Wiegel, Department of Hydraulics, College of Engineering, University of California, Berkeley, and F. P. Shepard and D. L. Inman of the Department of Geology, University of California at La Jolla, contributed counsel, unpublished material, and photographs. In Tillamook, Albert Kenny, Mr. and Mrs. R. H. Watkins, and Carl Sanders were especially helpful. Curtis Avery called attention to some interest- ing changes in the Nehalem region. B. A. Martin and Max Brainard contri- buted several critical items for the southern Oregon coast. Our colleagues at the University of Oregon gave freely of their time both in the office and in the field.Clyde Patton, Gene Martin, and Fritz Kramer of Geography, Ewart Baldwin and Ernest Lund of Geology, Leroy Det- ling, Stanton Cook, and Eugene Addor of Biology offered suggestions and aided in the identification of specimens. The Library staff aided in many ways; Martin Schmitt and Inez Fortt made available the uncatalogued mater- ial in The Oregon Collection. Roger Person drew most of the maps and dia- grams, David Smith checked references and read proof, and William Schetter analyzed sand samples. John Gierhart, who at the time of his death was studying the Oregon and Washington tidal marshes, contributed many ideas on coastal changes, through conversations and field trips with the principal investigator and through parts of an unfinished manuscript. Finally, special thanks are due Emily F. Dicken who, as field assistant, editorial assistant, and typist, is responsible for many of the details of this report. Samuel N. Dicken Carl L. Johannessen Bill Hanneson SOME RECENT PHYSICAL CHANGES OF THE OREGON COAST CHAPTER 1. DEFINITION OF THE AREA AND THE PROBLEMS Samuel N. Dicken At the time of white settlement, more than a century ago, most of the Oregon coast was retreating slowly while some sections, near the outlets of the large rivers, were advancing.The estuaries were filling and the coastal dunes were tending to become stabilized.Man's activities during the past cen- tury have tended to accelerate both erosion and deposition. The Indians burned small areas periodically but the white man logged, burned, and cultivated larger areas, thus increasing the sediment load of streams. Overgrazing down to the high-tide line changed the character of the backshore.During the last half-century man's structures, on and near the coast, have brought about striking changes.The natural changes are brought about by a number of interacting agents and materials - wind and waves, rain and sun, tide and currents, rock type and landform. Man's works have further complicated the problems and much more study will be necessary before the natural and human processes at work on the Oregon coast can be fully understood. Failure to understand them has cost hundreds of thousands of dollars in the past; in the future the amount will be measured in millions. SCOPE AND PURPOSE This report is concerned with some of the physical changes of the Oregon coast (from the California boundary to the Columbia River) which have occurred since settlement.More specifically, it includes changes of the beaches and the immediate backshore, of the active dunes near the shore, and of the estu- aries. Some parts of the report are of a more general nature, in an effort to place the specific studies in the proper perspective. The time span, arbitrarily-chosen, is the period since white settlement, a little more than a century. This is the time for which historical records are available to document the nature of the changes. The purpose of the report is to describe, measure, and explain some of the Oregon coast changes within the limitations of time and resources available.Special emphasis is placed on the beaches, dunes, and tidal marshes in the estuaries, where changes have occurred and are occurring. Many aspects of these three categories and many lines of investigation had to be left unstudied.It is hoped that the content of this report, as well as its shortcomings, will point out the need for further research. SOURCES A great variety of source materials is available for the study of coastal changes, some of it scattered 'In various libraries and unavoidably mixed up with records of little significance; some more readily avail- able. The old topographic charts of the U. S. Coast and Geodetic Survey, some of them dating back to the 1850's, were very useful. Some of these charts were mapped by the use of a plane table on the scale of 1:10,000 and show the nature of the shoreline and the backshore in more detail than moet present day maps. Comparison of these charts with recent aerial photographs has proved to be most rewarding.The old charts provide much specific information on the shore vegetation of the early days.Various editions of the Coast Pilot, first published in 1859, were most helpful; the most complete is the edition of 1889. U. S. Army Corps of Engineers reports from the late 19th century to the present have provided maps of historical interest and much useful information. Old ground photographs of the coast are available in quantity and comparison of these with very recent photographs has revealed many specific changes, espec- ially in vegetation. Journals, diaries, and first-hand descriptions of early travelers have been quite helpful, as have the reports of many scientists who have studied special aspects of the Oregon coast. Interviews with local residents, who recall word by word accounts of early conditions, have often pointed up specific changes. By far the most valuable source materials, however, are the aerial photographs of the Oregon coast. For many parts of the coast, good vertical coverage is available for the years 1939 and 1940: in a few cases aerial photographs are available for earlier years.Comparison of these with aerial photographs of 1960 and 1961 has given the most precise measure of changes in shoreline, landforms, and vegetation. Approximately 500 of these photographs were examined, many of them with stereoscope, in the course of this study. A few are reproduced in this report. Field work carried out for the duration of this study, 15 months, supplied much additional information and the means of interpreting and evaluating the sources mentioned above. The field work was long enough to observe many specific changes and especially to isolate the purely seasonal variations which have -1- limited meaning. Measurements were made of slopes and beaches;beach profiles were mapped; samples of sand, rock, and plants were collected forlaboratory analyses. PRE-SETTLEMENT CONDITIONS It is apparent that at the time of settlement the coast of Oregonwas in a state of slow change.For approximately 6000 years the sea level has been relatively constant and during this timeerosion and de- position have proceeded at a comparativelyuniform rate. To be sure, storms and floods often caused an unusual amount of erosion and deposition within a short period of time but, considered in terms ofcen- turies, it appears that conditions have been fairly uniform during the last 6000years. There are those who will disagree with this statement. Some students of shorelines believe thata lowering of sea level occurred 400 or 500 years ago with the result that, in places, a two meter terrace has been formed. No clearcut evidence has come to the attention of the authors that this has occurredon the Oregon coast. It appears that the beaches, the estuaries, and the dunes of the Oregon coast of 100years ago were approaching an equilibrium. This does not mean that conditionswere static; on the contrary, change was constant. Some of the changes were ofan oscillatory nature, such as the changing in the spits and bars of the lower estuaries. It is a part of the naturalprocess that the openings of the rivers in the coastal spits should shift from time to time.