Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
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Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandties in the last 150 years greatly altered the riverine landscape and salmonid habitats of the Puget Lowland. Archival investigations together with field studies of relatively undisturbed rivers make it possible to describe the landscape prior to settlement by Euro-Americans. Landforms, dynamics, an Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandd habitats in lowland river valleys and estuaries varied broadly with differences in regional geologic history. Rivers that incised a Holocene valleyCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
through Pleistocene glacial sediments typically had an anastomosing pattern with multiple channels, floodplain sloughs, and frequent channel-switching4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandlly had a single-channel meandering pattern, with oxbow lakes, infrequent meandercut-off avulsions, and vast floodplain wetlands. Because wood appears to have strongly influenced riverine dynamics at a wide range of scales, floodplain forests are central to river restoration. Archival sources can ch Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandaracterize species and diameters of trees in historical forests and the geomorphic, hydrologic, and geographic variables influencing them; process stuCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
dies indicate conditions and wood characteristics necessary for jam formation. Regional differences in channel morphologies, processes, suites of vall4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandeeded in restoring lowland river and forest ecosystems.80Reconstructing the Historical Riverine LandscapeRiver History AM) THE Puget Low LAM)A century and a half of development since European settlement has transformed the appearance and function of Puget Sound s riverine landscape. Human inhabitanc Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandy has been most extensive and landscape change most noticeable in lowland river valleys, eradicating or degrading much of the region’s historically riCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
chest and most abundant salmonid habitat (Sedell and Luchessa 1981; Beechie et al. 1994, 2001; Collins and Montgomery' 2001). This river-use history i4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandally simplified and biologically impoverished (e.g.. Vileisis 1997; McNeil 2000). However, the relatively-recently settled Puget Lowland is unusual in having remnant natural areas and a wealth of archival sources describing pre-settlement conditions (we use the term “presettlement” as an abbreviated Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland reference to “prior to settlement by Euro-Ameri-cans”). These circumstances make it possible to reconstruct on paper the historical river as an aid tCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
o undertaking river rehabilitation or restoration.The problem of reconstructing badly degraded landscapes or landscapes that no longer exist spans the4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandtorical ecology (e.g., Egan and Howell 2001). Environmental history, which includes a focus on understanding the political. social, and cultural forces behind landscape change and how those changes in turn shape society, overlaps with and complements historical ecology (e.g., White 1992; Whitney 199 Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland6). Reconstructing the riverine environment of Puget Sound can draw on the methods of these disciplines but also must be grounded in geology and proceCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
ss geomorphology, because the region’s riverine landscape is geologically young and physically dynamic, and its ecosystems are closely linked to physi4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland Stillaguamish to the 7,800 km2 Skagit. Steep mountain headwater slopes lessen in mountain valleys and decrease dramatically in the Puget Lowland. In the low land, deep, generally north-south trending troughs either partially filled w ith sediments or by Puget Sound or other water bodies, are a domi Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandnant topographic feature (Chapter 2). Repeated advances by the Puget Lobe of the Cordilleran ice sheet created these valleys at least in part by subglCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
acial fluvial runoff (Booth 1994). Sev-Collins, Montgomery and Sheikh81Figure 1. Location of watersheds and rivers in eastern Puget Sound.82Reconstruc4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandack, the Snohomish. Snoqualmie. Sammamish. Duwamish, and Puyallup Rivers (Figure I). These valleys hasc a low gradient and are typically 3 5 km wide. Other rivers cut across the lowland glacial fabric, and incised steeper and narrower (1-2 km wide) postglacial (Holocene) valleys. These include the u Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandpper Nooksack, the Stillaguamish. and Nisqually Rivers.Various post-glacial forces modified (and continue to modify) this Pleistocene legacy. HoloceneCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
fluctuations of sea level and isostatic rebound changed the extent of subaerial valley bottom (Beechie et al. 2001), especially in north Puget Sound 4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlanduamish Rivers (Beget 1982); remnants of lahar deposits since incised by fluvial erosion can be found in each of these three valleys. These lahars also extended the Skagit River delta greatly seaward (Dragovich et al. 2000). At least 60 Holocene lahars moved down valleys heading on Mount Rainier (Hob Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandlitt Ct al. 1998), many of which traveled into the White and Puyallup Rivers (Figure 1). Mount Rainier’s National Lahar traveled from the Nisqually RiCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
ver to Puget Sound less than 2,200 ybp (Hoblitt et al. 1998).These lahars have been most influential in shaping channels and habitats in valleys that 4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandt, Sauk. North Fork Stillaguamish. and Skykomish; each valley includes terraces of Pleistocene glacial and Holocene lahar sediments, through which the river has incised (Beechie et al. 2001). In the less-glaciated south, such lowland-to-mountain transitional valleys as the White and upper Puyallup a Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandrc more heavily influenced by the presence of lahar deposits. For example, the White River is cutting a deep canyon through deposits of the 5.600 yearCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
s before present (lloblitt et al. 1998) Osceola Mudflow. In this chapter, we concentrate on lowland rivers, but many of the concepts we develop can be4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandnts, especially those greatly changed by anthropogenic forces, is inherently uncertain. This uncertainty reflects the incomplete views through the available windows onto past landscapes as well as the spatial and temporal variability of landscape processes. In light of this uncertainty, how reliably Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland should historical reconstructions be viewed?Collins, Montgomery, and Sheikh83The answer depends on the methods used. Using independent methods with oCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
verlapping temporal and spatial scales, and cross-referencing between archival studies and field investigations can define and reduce uncertainty. By 4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandtives.Our reconstruction of the landscape is necessarily limited to conditions that existed in the mid I9'h century, or around the time when non-native settlers arrived, because for the time prior to the written record we can only make broader, less detailed descriptions using indirect field methods Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland. However, it is possible to supplement this snapshot-in-time with inferences about long-term (Holocene) landscape and ecosystem evolution and more raCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
pid change. For example, forest composition in the region probably attained modem characteristics approximately 6,000 ybp (Bamosky 1981; Leopold et al4. Reconstructing the Historical Riverine Landscape of the Puget LowlandBrian D. Collins, David R. Montgomery, and Amir J. SheikhAbstractHuman activit Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandthe time frame of a few centuries. We have recent analogs to draw on for understanding the effects of intermittent, dramatic disturbances to river valleys such as volcanic lahars (e.g., from the 1980 eruptions of Mt. St. Helens) and earthquake-associated uplift. Archival and field studies can adequa Collins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowlandtely characterize the changes occurring on decadal and more frequent time scales. Moreover, many agents of anthropogenic change over the last *150 yeaCollins_et_al_2003_Reconstructing_the_historical_riverine_landscape_of_the_Puget_Lowland
rs have been much more rapid than natural processes.We refer to the “historical” landscape rather than the “natural” environment, because people haveGọi ngay
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