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Lateral Channel Migration and Bank Erosion Along the Marys River and Selected Tributaries

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Lateral Channel Migration and Bank Erosion Along the Marys River and Selected Tributaries - • Lateral Channel Migration and Bank Erosion along the Marys River and Selected Tributaries A report prepared for the Marys River Watershed Council ! by Barbara ElIIs-Sugal, PhD Siuslaw National Forest December 1998 Table of Contents Introduction................. ," ....................................................................... 1 Methodology.......................................................................................... I Geologic and Geomorphic History of the Marys River. ........................................3 Recent History of the Marys River, Greasy Creek and Muddy Creek ........................5 Marys River ..................................................................................5 Discussion of Marys River Cross-Sections ............................................. 16 Greasy Creek ...................................... ,.........................................20 Discussion of Creek Cross Sections ............................................20 Muddy Creek ...............................................................................24 Discussion and Conclusions.......................................................................24 Marys River .................................................................................24 Greasy Creek ...............................................................................27 Recommendations..................................................................................28 Other Questions .....................................................................................30 Glossary..............................................................................................34 References...........................................................................................35 Contacts and Sources ..............................................................................36 Tables Table 1: Stream channel location and riparian vegetation for selected streams analyzed by air photo date .....................................................................................3 Table 2: Cahnges in the Marys River over time by reach .................................... 14 Table 3: Changes in length of Marys River stream reaches over time ..................... 14 Table 4: Sinuosity of the Marys River from mouth to Greasy Creek .......................16 Table 5: Marys River Cross-Sections ...........................................................19 Table 6: Greasy Creek Cross-Seetions ..........................................................20 Table 7: Comparison of areas of bank erosion with and without bank vegetation by year air photos were taken ..............................................................................26 List ofFigures Figure l: Location map ... , .,',.. " .. ,', .................... ' .. '" .,",." .. ,,, .... "., ...............2 Figure 2: Delta deposit ofthe Marys River, Corvallis topographic quad map ...............6 Figure 3a: Patterns of braided streams and large. old meanders can be seen in the fannland around Muddy Creek, 1936 air photo ............ ," .. , ... ,',.<" •••. , ....•....•. « .....7 Figure 3b: Patterns ofold drainage channels can be seen around the confluence of Muddy Creek with the Marys River, 1936 air photo ...... ,."' ...... ,... ,..... ""."." .........., .. ,_ .. .,8 Figure 4.: Muddy Creek meander belt width .....................................................9 Figure 4b: Close-up of Muddy Creek meander helt width .................................... 10 Figure 5: Reaches analyzed for length and sinuosity on the Marys River between Grea."iy Creek and its mouth .................................................................................12 Figure 6: Dramatic changes in the Marys River downstream of Greasy Creek can be seen in the 1994 photos ( Plate 3).......................................................................15 Figure 7a: Location of the cros.s-sections on the Marys River.with air pho[O .. ,"" ....... 17 Figure 7b: Location of the cross-sectjons on the Marys River ..........., .. , .. , ..... ,... ". 18 Figure Sa: Greasy Creek cross.-s.ections location with air photo ...... _......... " ......." ... 21 Figure 8b: Greasy Creek cross-sections location ...", .... ,.... ' .... ,. , ................ , .. , .... 22 Figure 9: Greasy Creek cross-sections....... ,... " .. ", ... ". ", ....... ,.........,........... ,..23 Figure 10; 1994 air photo showing bank: erosion where riparian vegetation is lackjng... 27 Figure Jla: Meander bell width in the Corvallis area.. ,................................ " ... .32 Figure lIb: Meander belt width south of Philomath..........................................33 List of Plates Plate 1: Comparison of 1936 and 1956 Marys River chaI1nellocation. Plate 2: Comparison of 1956 and 1963 Marys River channel location. PIa'" 3: Comparison of 1963 and 1970 Marys River channel location. Plate 4: Comparison of 1970 and 1994 Marys River channel location. Plare 5: All Marys River channel locations mapped from air photos. Plate 6: Extent of the floodwater during the 1996 flood. Plate 7: Marys. River cross Plate 8: Greasy Creek channellocation in 1956 and 1994. Plate 9: Muddy Creek channel location 1fl 1936, 1956 and t994. Plate 10a: Difference in riparian vegetation, 1936-1994. Marys River and Muddy Creek (north part) Plate lOb: Difference in riparian vegetation, 1936-1994, Muddy Creek (,outh part) Lateral Channel Migration and Bank Erosion along the Marys River and Selected Tributaries A report prepared for the Marys River Watershed Council by Barbara Ellis-Sugai, PhD Siuslaw Natjonal Foresl Introduction The Marys River and most of its tributaries drain the eastern slope of the Coast Range west of CorvaUis. The exception is Muddy Creek. a tributary system that flows north for 15 miles along the western edge of the \Villarnette Valley and joins the Marys River Corvallis and Philomath. The Marys Rjve-r enters the \Villamette River at Corvallis (Figure 1)_ The purpose of this study is to document where lateral channel migration and bank erosion have occurred, and possible causes for bank erosion along the Marys River and selected tributaries. In order to understand why rivers change over time, it is necessary to understand the geologic and geomorphic setting of the river system and the Jand use history that influences channel stabiHty. Methodology Digital ortboquad aerial photos from 1994 and other map data were obtained from the Bemon County GIS (geographical information systems) Department These digital air photos served as the base map for creating new maps that show the location of selected stream channels and the extent of riparian vegetation over time, ArcView 3.0 software wa... used to ereate and analyze the maps made for this study. Historic air photos were obtained from the Oregon State University library. Air photos were available for the following years: 1936 (air photos were only taken of the Willamette Valley), 1956, 1963, and 1970_ Stream channel1ocations aud the extent of dpadan vegetation that consisted of trees and brush were traced onto drafting film I Figure 1: Location map of the Marys River, Greasy Creek and Muddy Creek. 2 (mylar). These mylar maps were reduced to the same scale as the 1994 stream maps. and the historic location of the stream channels were overlain with the 1994 channel location. Historic channel locations were then digitized onto new layers (computer files) using ArcView 3.0. TabJe 1 shows which streams were analyzed for each year air photos were available. Table 1: Stream channel location and riparian vegetation for selected streams analyzeI db'Dyate hoto date. , , , 1936 1957 1963 1970 1994 , : Stream c c c c c c,2 c: .2 e.Q ro- we ii ·2 w c a,g ",- wc ro- c 0 -$ co co -J!! "!:s c 0 c::;::: c:;..::< 0::; e:;::: c·- c:;::: -"mm. !l.", 0.'" '" " .!l-. .q .c 0 li,- '" '" " -0'" ' ""8u_ ti: > if u_ u..Q"" n::, ""80_ oc>: ; Marys River above X : Greasv Creek i Tum Tum River X Marys River from X X X X X X X X X X , , Greasy Creek to , , mouth , , , Greas Creek X , X X Ix , Muddy Creek :X X X X X X Cross-sections were measured on Greasy Creek and on the Marys River south of Philomath. Cross-sections add a third dimension to a stream's description. Several pieces of data can be collected from a cross-section. The cross-sectional area is necessary for calculating discharge, The ratio of the width to the depth of the stream is useful for classifying the stream type. The amount of entrenchment, or downcutting into the floodplain. can be calculated from a GeolQgic and Geomorphic History of tbe Marys River Before uplift of the Coast Range began at approximately 25 million years ago (mid-Oligocene) (Orr, et 01 .• 1992), the Marys River was a fairly large river that flowed west from the Cascades to the Pacific Ocean. As uplift of the coastal mountains began. the Mary'S River began to downeut into the volcanic bedrock of the Coast Range. Today. these incised meanders of the Marys River can be seen west of Greasy Creek. Eventually, the uplift of the Coast Range cut the Marys River into two distinct rivers. 3 The Marys River on the east side of the Coast Range crest reversed flow and began to flow into the Willamette Valley. The Marys River west of the Coast Range crest became the modem Yaquina River. This larger. older continuous river system left behind three pieces of evidence: for its fonner existence: 1) 1be incised meanders are much larger in the upstream portions of the Marys River in the Coast Range. as compared to the meanders
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