The Ore Bin - Oregon Department of Geology and Mineral Industries

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For these reasons, removal of the sand by mining operations probably disrupted the natura I budget of beach sand, the ba lance of sand gai ns and losses on the beach. With decreased volume, the beach was less able to protect the coastal property from wave attack, and acce lerated erosion resulted. Therefore, although cycles of erosion to Siletz Spit are natural and are known to have occurred prior to beach sand mining, the mining operations probably caused increased erosion. Beach sand mining has subsequently been stopped. Present Status of Erosion on Siletz Spit The winters of 1973-74 and 1974-75 were mild, and the few storms that did occur were not intense (Komar and others, 1976). Erosion is again occuring during this winter (1975-76), centered principally near the park and at the far north end of the spit, near the northernmost house on the spit. In both cases the erosion is again caused by rip currents hollowing out the beach. The erosion to the north spit area wou Id have threatened one or two houses except that adequate riprap had been previously installed. Some of the lots that were eroded in 1972-73 have been subsequently restored (Figure 10). These are either not protected or are inadequately protected: another winter of intense storms could bring renewed erosion. During this winter (1975-76) no rip current is located offshore from this area, and there is no erosion. Some houses for which riprap was installed in 1972-73 could be endangered by future erosion because the riprap protection is inadequate. In some cases the riprap has partially eroded, exposing the dune sands (Figure 11). This riprap was installed hastily in order to save the houses at the time of severe erosion in 1972-73, and installation did not follow the established engineering procedures for riprap construction. Even more important, stones of inadequate size were used because of their availability: these are easily washed away by waves. Thi sill ustrates another lesson to be learned from the erosion of Siletz Spit. When homes are constructed in sandy areas close to the ocean, there is a strong possibility that subsequent erosion may necessitate the installation of riprap at considerable expense. Some homeowners have already spent about $15,000 in their defense against the ocean, and more expense may be required. It is now necessary that the area be uniformly protected with riprap. As we have seen from the experience at Siletz Spit, if one neighbor does not protect h is property, the defense wi II be breached and the erosion may come from the side rather than from the ocean-front. When sand areas near the ocean are deve loped without adequate setback the entire area must be protected, perhaps by the developer. The necessary placement of riprap acts to limit be9ch access from the homes. Riprapalso interferes with the scenic aspects of the coast that draw 128
29 October 1973 10 June 1975 Figure 10 . Restoration of the lots 228 and 229. Compare with Figures 3 and 4. 129
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Volume 38, No. I January 1976 STATE
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State of Oregon Department of Geolo
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The search for uranium was carried
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Although difficulties have been exp
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Table 1. Oil and gas drilling in Or
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GEOTHERMAL ACTIVITY IN 1975 Donald
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Richard Couch of Oregon State Unive
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Abandonment cementing operations at
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Table 5. Federal geothermal lease s
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21. Ferruginous bauxite and high-al
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8. Geology of Greenhorn District, S
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Volume 38, No.2 Februory 1976 STATE
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Figure 1. View of Mount Hood from s
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Recent Observations on Mount Baker
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A log of all anomalies has been mai
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Figure 6. Breakup of ice within cra
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Figure 8. Photo of East Breach area
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OUR CHANGING RESOURCE CLIMATE Ralph
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FEDERAL MINERALS POLICY OUTLINED BY
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The Ore Bin Published Monthly By ST
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Our research to determine heat flow
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ash-flow tuff. Regional heat flow i
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OPEN FI LE REPORTS ISSUED Oregon De
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AGE OF HOWARD 2 MONTHS, ME 10 The t
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STE ENS MOUN TA I N Volume 38, No.4
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the mountain into three distinct to
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Figure 5. Pike Creek Formation at t
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Figure 7. View east up Little Blitz
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Volume 38, No.5 May 1976 STATE OF O
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Figure 1. Massive rack failure near
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Douglas County. In the 1950's over
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Figure 8 . Damage to the picnic gro
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waves occurred at night during the
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high rainfall, rapidly melting snow
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Beaulieu, J.D., and Hughes, P.W., 1
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Kleppe told the audience that Inter
Page 112 and 113: State of Oregon Department of Geolo
Page 114 and 115: crusta I blocks. I t has been exten
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Page 118: exposed and structural relationship
Page 123: Schmela, R.J., and Palmer, L.A., 19
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Page 140: Acknow ledgements This work is a re
Page 143: Components of a 1975 Chevrolet Capr
Page 146: PITTSBURG BLUFF FOSSILS DESCRIBED "
Page 153 and 154: 28 December 1972 19 January 1973 .-
Page 155 and 156: Figure 4. View of both houses of Fi
Page 157 and 158: -.-, • Figure 6. logs had been sa
Page 159: Figure 8. Irregular shorel ine of b
Page 164 and 165: In 1875 the width of the spit, C, w
Page 169: Volume 38, No.9 September 1976 STAT
Page 172: (often minute) to medium vessels, t
Page 181 and 182: (above) in its increased dorso-vent
Page 183: MINERAL SYMPOSIUM ANNOUNCED The Pac
Page 186: KEEP IN TOUCH! Of course you notify
Page 191: State of Oregon Department of Geolo
Page 197 and 198: " " " EASY GIVING" " " ORE BIN READ
Page 199: TREASURES FROM OLD ORE BINS 25¢ pe
Page 204 and 205: 450 ___ -+---+-________ --+ _____ 4
Page 206: BLM ISSUES OIL AND GAS LEASES IN WE
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The Ore Bin Published Monthly By ST
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that some flows, such as the Roza B
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w I I I I 30 60 N . - .t. ..! + S N
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VOLlfIE 38, I'I:J, 12 DeCEMBER 1976
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Ancient terraces: Ancient elevated
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00 00 A u o EJ EXPLANATION Beach sa
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DESCHUTES COUNTY BULLETIN PUBLISHED
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The Ore Bin - Oregon Department of Geology and Mineral Industries

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