Name: Date: Team Name: Team Members: Our goal today is to characterize some fluvial sediments, at two different sites along the Mad River, and within each site. We will form teams and describe sediments in a few locations. When taking notes of our observations, we want to take the notes in the same order each time, as usual. We will form groups of three or four. We will learn: How particle size distributions are controlled by geomorphic setting How gravel orientation may be related to geomorphic setting There will be two stops along the Mad River. The first stop will be at the Mad River pump station park. We will map the sediment particle size distribution along a cross sectional transect perpendicular to river flow. We will prepare a plan view map and a vertical cross section. We will collect Wolman Pebble Count Fig. 1. Process domains defined by (a) Schumm (1977) (as depicted by Kondolf, 1994) and (b) Montgomery (1999). 1 P age
Fig. 2. Channel pattern (meandering, straight, and braided) as a function of channel slope and bankfull discharge. Leopold, L.B., Wolman, M.G. (1957). Particle size data at stations based upon an initial review of the sedimentary / geomorphic environments present. These data will be entered into a spreadsheet and plotted in various ways. The second stop will be along a tributary to the Mad River, immediately upstream of its Fig. 3. Schumm s (1963a, 1977, 1981, 1985) classification of alluvial rivers. confluence with the Mad 2 P age
River. We will also prepare a plan view map, vertical cross section, and particle size data. We will supplement these data with a sediment clast imbrication analysis. The particle size data will be plotted like for stop 1. The clast imbrication data will be plotted on a stereo net, using poles to planes and plunge axis plots. This may be done by hand or with software. Sedimentary Environments Fluvial sedimentary environments can be spatially related to different fluvial geomorphic processes. When interpreting fluvial sediments and rocks, having a knowledge about what particle size distributions occur in different geomorphic settings improves the likelihood that one s interpretation is correct. To do this, we must know a little about fluvial processes and different geomorphic settings. One way to approach this is to consider geomorphology, which implies that form implies process. There are many uses for channel classification systems (simplifying Fig. 4. Schumm s (1977, 1981, 1985) classification of channel pattern and response potential as modified by Church (2006). complex models for interpreting the complex continuum of processes and conditions within a landscape 3 P age
by identifying places that function in a similar manner, interpreting and assessing entrainment, transport, and depositional conditions, etc.). We will use some of these classification systems to help us visualize the variation in fluvial sedimentary environments. Process Domains: Schumm (1977) divided rivers into sediment production, transfer, and deposition zones, providing a process based view of sediment movement through river networks over geologic time (Figure 1A). Process domains are portions of the river network characterized by specific suites of interrelated disturbance processes, channel morphologies, and aquatic habitats, and at a general level roughly correspond with source, transport, and response reaches in mountain basins (Figure 1B; Montgomery, 1999). Classification of rivers using process domains is a coarse filter (typically lumping several channel types), but it identifies fundamental geomorphic units within the landscape that structure general river behavior and associated aquatic habitats. Figure 5. Map and diagrammatic schematic views of a drainage basin to illustrate the concept of coupling between a stream channel and adjacent hillside slopes. Near the upstream limit of the decoupled reach there will usually be a significant partially coupled reach, where stream channels move against, and then away from adjacent hillslopes. On the left side of the diagram are schematic graphs of characteristic grain size distributions through the channel system. In each graph, the next upstream distribution is shown (dashed line) so the intervening modification by stream sorting processes may be directly appraised. On the right hand side of the diagram are graphs to illustrate the attenuation of sediment movement down the system. Attenuation is the consequence of increasing mobility of finer material farther downstream, tributary confluences with variations in runoff timing, and of diffusive processes associated with channel flow. Channel Pattern: Most river classifications that have been developed involve classification of channel pattern (i.e., planform geometry, such as straight, meandering, or braided), which can be broadly 4 P age
divided into two approaches: (1) quantitative relationships (which may be either empirical or theoretical) and (2) conceptual frameworks. Quantitative relationships Lane (1957) and Leopold and Wolman (1957) observed that for a given discharge, braided channels occur on steeper slopes than meandering rivers (Figure 2). Conceptual frameworks Schumm s (1960, 1963, 1968, 1971a, b, 1977) work on sand and gravel bed rivers in the Great Plains of the western U.S. emphasized that channel pattern and stability are strongly influenced by the imposed load of the river (size of sediment and mode of transport) and the silt clay content of the floodplain (providing cohesion necessary for the development of river meandering). Based on these observations, Schumm (1963, 1977, 1981, 1985) proposed a conceptual framework for classifying alluvial rivers that related channel pattern and stability to (1) the silt clay content of the banks, (2) the mode of sediment transport (suspended load, mixed load, bed load), (3) the ratio of bed load to total load (a function of stream power, sediment size, and supply), and (4) the slope and width to depth ratio of the channel (Figure 3). Schumm s (1963a, 1977, 1981, 1985) classification has since been refined to include a broader range of channel types (Mollard, 1973; Brice, 1982), including steeper morphologies present in mountain rivers (Church, 1992, 2006; Figure 4). Channel pattern classification approaches are typically descriptive (associating physical conditions with channel morphology, but not explaining the underlying processes) or involve a mixture of descriptive and process based interpretations. A comprehensive presentation of different channel classification systems is in Buffington and Montgomery (2013). Channel elements in high gradient channels (a) step pool system; (b) pool riffle bar system. 5 P age
Church (2002) presented a figure that shows how sediment size may vary in a drainage basin, a conceptual approach listed above (Figure 5). Church (2002) also presents a figure that shows how particle size may vary in different sedimentary settings (Figure 6). Bunte and Abt (2001) present a schematic longitudinal and planform view of five stream types at low flow. (A) Cascade with nearly continuous highly turbulent flow around large particles; (B) Step pool channel with sequential highly turbulent flow over steps and more tranquil flows through intervening pools; (C) Plane bed channel with an isolated boulder protruding through otherwise uniform flow; (D) Pool riffle channel with exposed bars, highly turbulent flow over riffles, and more tranquil flow through pools; and (E) Dune ripple channel with dune ripple bedforms (Figure 7). Fig. 7. Schematic longitudinal (left) and planform (right) illustration of the five stream types at low flow: (A) Cascade with nearly continuous highly turbulent flow around large particles; (B) Step pool channel with sequential highly turbulent flow over steps and more tranquil flows through intervening pools; (C) Plane bed channel with an isolated boulder protruding through otherwise uniform flow; (D) Pool riffle channel with exposed bars, highly turbulent flow over riffles, and more tranquil flow through pools; and (E) Dune ripple channel with duneripple bedforms. Finally, Rosgen (1994) relates stream form to slope, cross section, plan view, and particle size (Figure 8). 6 P age
An illustration that attempts to bring together the major factors that control entrainment, transport, and deposition in a fluvial system is presented in Figure 9. In the Lane balance diagram, flow sediment interactions determine the aggradational degradational balance of river courses. (a) The river maintains a balance, accommodating adjustments to the flow/sediment load. (b) Excess flow over steep slopes, or reduced sediment loads, tilts the balance towards degradation and incision occurs. (c) Excess sediment loads of a sufficiently coarse nature, or reduced flows, tilt the balance towards aggradation and deposition occurs. The arrows on (b) and (c) indicate the way in which the channel adjusts its flow/sediment regime to maintain a balance. Wolman Pebble Count Fig. 8. Rosgen s stream classification. Longitudinal, cross sectional and plan views of mayor stream types (top); Cross sectional shape, bed material size, and morphometric delineative criteria of the 41 major stream types (bottom). The composition of the streambed and banks are important facets of stream character, influencing channel form and hydraulics, erosion rates, sediment supply, and other parameters. Observations tell us that steep mountain streams with beds of boulders and cobbles act differently from low gradient streams with beds of sand or silt. You can document this difference by collecting representative samples of the bed materials using a procedure called a pebble count. In this case, one would collect particle size 7 P age
Fig. 9. The Lane balance diagram. Flow sediment interactions determine the aggradational degradational balance of river courses. (a) The river maintains a balance, accommodating adjustments to the flow/sediment load. (b) Excess flow over steep slopes, or reduced sediment loads, tilts the balance towards degradation and incision occurs. (c) Excess sediment loads of a sufficiently coarse nature, or reduced flows, tilt the balance towards aggradation and deposition occurs. The arrows on (b) and (c) indicate the way in which the channel adjusts its flow/sediment regime to maintain a balance. Modified from Lane (1955). data across the entire fluvial landscape within the reach of river or stream, using the zigzag data collection pattern (Bevenger and King, 1995). Alternately, one could analyze different geomorphic settings within a reach of a river or stream. In this case, one would limit their station analyses to those specific geomorphic settings. We will be analyzing Fig. 10. Clast axes: (A) Long Axis, (B) Intermediate Axis, and (C) Short Axis. specific geomorphic settings at our first stop and a hybrid approach at our second stop. Regardless of which method one uses, for each data collection station, the following are the general steps. Averting your gaze, pick up the first particle touched by the tip of your index finger at the toe of your shoe/boot/wader. Measure the intermediate axis (neither the longest nor shortest of the three 8 P age
mutually perpendicular sides of each particle picked up; Axis B; Figure 10). Measure embedded particles or those too large to be moved in place. For these, measure the smaller of the two exposed axes. Call out the measurement. The note taker tallies it by size class and repeats it back for confirmation. There are many different size class schema. For this lab, use the size classes presented in Table 1. Clast Orientation Clast imbrication is an indicator of modern current and palaeocurrent direction. There are many aspects that are important to consider and these are detailed in Bunte and Abt (2001). For our data collection in this lab, we will collect the strike and dip for a number of clasts at stop 2 of our field trip (Figure 11). For clasts that have equal B and C axis measurements (a roller ), collect the data as trend (compass orientation; the same as strike) and plunge (angle below the horizontal plane; Figure 12). Many people use a small sheet of rigid aluminum to help determine the orientation of the clasts that one is measuring. The instructor will have small pieces of cardboard for those without a sheet of aluminum. Basically, hold the card (aluminum or cardboard) with the flat dimensions of the card aligned with the A B axis direction. Then use one s pocket transit to measure the strike and dip of the orientation of the card. Have one person make observations, one person collect the data, and the third person locate the station on the map and the cross section. Rotate these roles during the cross section transect. Table 1. Clast Site Classes Fig. 11. Strike and Dip. From Dr. M.H. Hill at Jacksonville State University here: http://www.jsu.edu/dept/geography/mhill/phylabtwo/lab4/dipf.html 9 P age
Stop 1: Mad River at the pump station park Here we will conduct our first sediment sampling transect. We will conduct a single river flow perpendicular crosssection transect along the river, perpendicular to the flow. The crosssection transect will extend from the wetted edge, southward, across the gravel bar, and up to the edge of the vegetated floodplain. Take a look at the cross section transect and think about the different sedimentary Fig. 12. Orientation and Plunge. From: http://www4.ncsu.edu/~fodor/mea101.html environments along the crosssection transect. Choose three pebble count stations. We will conduct a Wolman Pebble Count at stations in each of these sedimentary environments. One person should make the observation and the other two should take notes. Rotate these roles during the lab, at each of the three stations. Make sure that everyone has a full set of these data observations in their own notebooks. This might involve making electronic scans of your notebooks after the field trips is over (to save time). Prepare a plan view and cross sectional view of your cross section transect. Distances will be based upon your paces and the vertical changes in elevation will be estimated. Make sure that your group s maps and cross sections generally match. Label your stations on the map and the topographic cross section. You will include these illustrations in your report. Pebble count data will be entered into an electronic spreadsheet. Prepare two plots: (1) a volume percent frequency distribution and (2) a cumulative percent distribution. Plot each sample location with a different symbol. Stop 2: Mad River upstream of the Blue Lake Bridge Here we will conduct our second sediment sampling transect. We will conduct a single transect along this tributary to the Mad River, Just upstream of the confluence. Each team will prepare a topographical 10 P age
cross section, using a stadia rod and pocket transits. Each team will sample the particle size distribution at evenly spaced stations across the river flow perpendicular cross section transect. Finally, each team will collect clast imbrication data for about 10 clasts in each sedimentary environment. We will set up the cross section transects at one river mile position, and collect clast orientation data upstream of the cross section transect. Report Meet with your group sometime after the field trip is over. Discuss your observations in the field, the data, the results, and what you learned during and after the field trip. You might want to meet twice, before you do your analyses and after you perform your analyses. If you work together, feel free to share the same spreadsheet within your group (the data entry is time consuming). I would like each student to prepare their own plots. Prepare a report and submit electronically to Jason.Patton@humboldt.edu. This lab is due prior to class two weeks from the day of the field trip. I will not accept hard copies of your report. The filename needs to be in the correct format or you will miss out on some points!!! The name format is in the syllabus. The report should be in a standard format (e.g. introduction, methods, results, discussion, and conclusion). I have placed a writing guide on the website. The report should include tables of your data, your maps, and your cross sections. Each table, map, and cross section needs to have a figure caption. References: Bevenger, Gregory S.; King, Rudy M., 1995. A pebble count procedure for assessing watershed cumulative effects. Res. Pap. RM RP 319. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 17 p. Brice, J.C., 1982. Stream channel stability assessment. US Department of Transportation, Federal Highway Administration Report FHWA/RD 82/021, Washington, DC, 42 pp. Buffington, J.M., Montgomery, D.R., 2013. Geomorphic classification of rivers. In: Schroder, J. (Editor in Chief), Wohl, E. (Ed.), Treatise on Geomorphology. Academic Press, San Diego, CA, vol. 9, Fluvial Geomorphology, p. 730 767. Bunte, K. and Abt, S. R. 2001. Sampling surface and subsurface particle size distributions in wadable gravel and cobble bed streams for analyses in sediment transport, hydraulics, and streambed monitoring. Gen. Tech. Rep. RMRS GTR 74. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 428 p. Church, M., 1992. Channel morphology and typology. In: Carlow, P., Petts, G.E. (Eds.), The Rivers Handbook. Blackwell, Oxford, UK, pp. 126 143. Church, M., 2002. Geomorphic thresholds in riverine landscapes. Freshwater Biology 47, p. 541 557. Church, M., 2006. Bed material transport and the morphology of alluvial rivers. Annual Review of Earth and Planetary Sciences 34, p. 325 354. 11 P age
Kondolf, G.M., 1994. Geomorphic and environmental effects of instream gravel mining. Landscape and Urban Planning 28, p. 225 243. Lane, E. W., 1955. The importance of fluvial morphology in hydraulic engineering. Proceedings, American Society of Civil Engineers, v. 81, Paper 745, pp. 17. Lane, E.W., 1957. A study of the shape of channels formed by natural streams flowing in erodible material. U.S. Army Engineer Division, Missouri River, Corps of Engineers, MRD Sediment Series no. 9, Omaha, NE, 106 pp. Leopold, L.B., Wolman, M.G., 1957. River channel patterns: braided, meandering, and straight. U.S. Geological Survey Professional Paper 282 B, Washington, DC, p. 39 84. Mollard, J.D., 1973. Air photo interpretation of fluvial features. Fluvial Processes and Sedimentation. National Research Council of Canada, Ottawa, ON, p. 341 380. Montgomery, D.R., 1999. Process domains and the river continuum. Journal of the American Water Resources Association 35, p. 397 410. Rosgen, D.L., 1994. A classification of natural rivers. Catena 21: 169 199. Schumm, S.A., 1960. The shape of alluvial channels in relation to sediment type. U.S. Geological Survey Professional Paper 352 B, Washington, DC, pp. 17 30. Schumm, S.A., 1963. A Tentative Classification of Alluvial River Channels. U.S. Geological Survey Circular 477, Washington, DC, 10 pp. Schumm, S.A., 1968. Speculations concerning paleohydrologic controls of terrestrial sedimentation. Geological Society of America Bulletin 79, p. 1573 1588. Schumm, S.A., 1971a. Fluvial geomorphology: channel adjustment and river metamorphosis. In: Shen, H.W. (Ed.), River Mechanics. H.W. Shen, Fort Collins, CO, p. 5 1 5 22. Schumm, S.A., 1971b. Fluvial geomorphology: the historical perspective. In: Shen, H.W. (Ed.), River Mechanics. H.W. Shen, Fort Collins, CO, pp. 4 1 4 29. Schumm, S.A., 1977. The Fluvial System. Blackburn Press, Caldwell, NJ, 338 pp. Schumm, S.A., 1981. Evolution and response of the fluvial system, sedimentological implications. In: Ethridge, F.G., Flores, R.M. (Eds.), Recent and Nonmarine Depositional Environments. SEPM (Society for Sedimentary Geology), Special Publication 31, Tulsa, OK, p. 19 29. Schumm, S.A., 1985. Patterns of alluvial rivers. Annual Review of Earth and Planetary Sciences 13, p. 5 27. 12 P age