Lab 6: Fluvial Processes Instructions Watch the lecture on fluvial…

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Question Lab 6: Fluvial Processes Instructions Watch the lecture on fluvial… Lab 6: Fluvial Processes Instructions Watch the lecture on fluvial processes, the stream system, stream erosion, transportation, and deposition, and stream and channel patterns. Also, view the video on stream velocity, slope, discharge, and shape. After you have reviewed the lectures and the video, use this document to work through your lab. After you have finished working through the lab, download the worksheet titled “Lab 6 – Fluvial Processes Worksheet” in Microsoft Word and type in your answers for each question. Once you have finished answering all questions, submit your worksheet online in the link titled “Lab 6 – Fluvial Processes”. Once your lab instructor grades those questions, your lab grade will be updated to the correct grade. Goals o Observe stream data from the San Marcos River in Central Texas, calculate its discharge, and estimate the velocity. o Understand Manning’s equation to calculate stream velocity. o Identify and analyze daily mean values of surface stream flow (in ft3 /s) from the United States Geological Survey (USGS) website for West Branch Mahoning River at Wayland OH. Key Terms / Concepts Fluvial Surface Runoff Surface Erosion Stream Stream Discharge Stream Ordering Stream Corrosion Hydraulic Action Stream Abrasion Stream Transportation Stream Velocity Stream Width/Depth Manning’s Equation Wetted Perimeter USGS Roughness Co-efficient For Lab 6 do the following: • Print out this lab instructions and work through the problems. • Download “Lab 6- Worksheet” in Microsoft Word o Using the questions from this lab below, fill in your answers on the worksheet. Show all work. o Upload your worksheet to the link titled “Lab 6 Fluvial Processes” Fluvial Geomorphology In this lab exercise you will observe data from the San Marcos River in Central Texas, calculate its discharge, and estimate velocity. You will use the Mannings equation to calculate velocity. Mannings Equation calculates the average velocity and is a more accurate way to determine stream velocity. This equation takes in all characteristics of a stream. Mannings equation calculates the average velocity of a stream taking into account: • The slope of a channel • The depth of the water • The roughness of the channel • The shape of the channel Some of this quantitative data will directly be given to you for this exercise in understanding how to calculate Mannings Equation. Refer to chapter 14 of your textbook for background on fluvial processes and stream discharge. For this lab you will be calculating stream discharge for the San Marcos River in Central Texas, and also gather real time stream data for the West Branch Mahoning River in Ohio from the USGS website. **Credit will not be given if you do not show your work and also if you forget your units when you submit your answers** Section A: Stream Discharge Stream discharge is the amount of water that passes through a cross-section of a streams channel in a specific amount of time. Stream discharge affects velocity which determines a streams ability to erode its channel and transport sediment (Shankman 2004). Discharge is calculated as cfs (cubic feet per second) or cms (cubic meters per second). For this lab you will be using cms. Discharge (Q) is calculated by the equation: Q = AV? A = cross-sectional area of the water flowing in a channel V = Average velocity of the water Source : http://www.trincoll.edu/~cgeiss/GEOS_112/discharge/s_channel.jpg Using your data from the San Marcos River determine the cross-sectional area (A) of the stream. Imagine that you went out to the river and measured the width and depth of stream. This data is given to you below. Steps: • Measure the width of the stream. Width = 18.2 meters • Measure the depth of the stream. Depth = 2.8 meters 1. Calculate the cross-sectional area.?(width X depth will be in square meters (m2) Cross-sectional area (A) = _________________ (1pt) Section B: Stream Velocity Average velocity is expressed as meters/second (m/s) and can be determined by timing the passage of a float such as a stick or a rubber duck along a known distance. For example, if your stick takes 20 seconds (s) to go 60 meters (m), then 60m/20s = 3 m/s. Your float would travel by stream at 3 meters per second. For this exercise, use a distance of 15.2 meters (50 feet) and assume you use a tape measure to determine the distance along the river. Imagine we as a class have ventured out into the field and collected 10 time trials along the San Marcos River. A person will drop the float in the water and someone who is 15.2 meters (50 feet) from the starting point will time the float as it moves along the distance using a second hand on their watch. A total of 10 trials will be done and then the average velocity in meters per second can be calculated. The velocity measurements are repeated 10 times in the table below. The quantitative data is given to you. For example, on trial one, it took the float 17.31 seconds to float 15.2 meters. A total of 10 trials was conducted. Observations 1 2 3 4 5 6 7 8 9 10 Distance (meters) 15.2 15.2 15.2 15.2 15.2 15.2 15.2 15.2 15.2 15.2 Time (seconds) 17.31 19.95 19.13 23.70 19.15 21.00 21.13 20.48 21.32 20.09 Velocity (m/sec) Calculate the velocity for each trial in the chart and then calculate the average velocity (V) by totaling up all 10 trials in the third row and divide by 10. This will give you the average velocity (V) in meters per second (m/s). 2. Calculate average velocity (V): ____________________________ (2pts) Discharge (Q) To calculate discharge (Q), multiply the cross-sectional area (A) x average velocity (V). Q = AV This will be in cubic meters per second. (m3 /sec) 3. Q = ____________________________________ (1pt) Daily Flow What is the daily volume of water that flows through this river? Your answer should be in cubic meters per day (m 3 /day). To do this multiply the discharge times 60 X 60 X 24. 60 (60 seconds / 1minute) X 60 (60 minutes / 1 hour) X 24 (24 hours / 1 day) 4. Daily flow: ______________________________ (1pt) Section C: Wetted Perimeter You will need to measure the portion of water in the stream that comes in contact with the channel bank. This must be in meters (m). The wetted perimeter can be calculated as width plus 2 times the depth (w + 2d). It is the length of the channel cross-section that is wet. For this lab we will approximate the wetted perimeter by using the channel width plus two times the average depth (w + 2d). The wetted perimeter is calculated for you. Width (w) Wetted Perimeter = 23.8 m3 Depth (d) Depth (d) Section D: Stream Gradient – Slope (S) Stream gradient is a ratio of the elevational difference between two points along the stream and the length of the channel or distance between them. The steeper the gradient (slope), the faster the water will move within the channel. For this exercise, we will be using a slope gradient of 2 percent. Slope – .02% Rise is the elevational difference between two points on the channel Run is the distance between the points Slope = rise/run Section E: Roughness Coefficient (n) Water moves through a stream at a faster rate when its channel is smooth and straight. Channels that meander and have obstructions are irregular and the water moves at a slower velocity. Channel roughness is a measure of channel characteristics that directly affect velocity. This includes channel configuration (straight or meandering), the presence of vegetation, boulders, and smooth or irregular channel (sides and bottom) (Shankman 2004). As a rule, as channel roughness increases, its velocity decreases. For this exercise we will be using 0.035 roughness coefficient (n). See table below for approximate values for (n). Alluvial Stream: Straight, clean channels 0.030 Straight, weedy or with boulders 0.035 Clean winding channels 0.040 Mountain Stream: Cobbles and boulders 0.050 Gravel bottom 0.030 Sand bottom 0.020 Section F: Mannings Equation You calculated velocity earlier in the exercise using only the surface of the river. For the remainder of this exercise, you will use Mannings equation to calculate velocity. Mannings Equation calculates the average velocity and is a more accurate way to determine stream velocity. Mannings equation calculates the average velocity of a stream taking into account all the characteristics of a stream such as the slope of a channel, the depth of the water, the roughness of the channel, and the shape of the channel. By using the Mannings equation, velocity is controlled by the following channel characteristics: hydraulic radius, channel slope, and roughness of channel. Hydraulic radius (R) – the measure of the proportion of water in a stream that comes in contact with the channel bed or banks. Refer to section A for cross- sectional area and section C for wetted perimeter formulas. Show your work in the space below. R = cross-sectional area / wetted perimeter 5. R = _______________________________ (2pts) Channel slope (S) s = .02 Roughness of channel (n) n = .035 Mannings Equation V = 1.0 * R.67 * S.5 n You will need to use a scientific calculator to calculate the equation. Tor the hydraulic radius (R) and slope (S), you will need to use the Yx key on the calculator. For example, 7.13.67 = 3.72. On your calculator, punch in 7.13, and then hit the Yx and punch in .67. V= m/sec R = hydraulic radius (cross-sectional area of the channel divided by the wetted perimeter) S = slope or gradient of the channel n = roughness coefficient Enter the San Marcos river stream data in the table below from the previous sections. Width (w) Average Depth (d) Cross-sectional area (A) Wetted Perimeter (w + 2d) Hydraulic radius (R Stream gradient (S) Roughness Coefficient (n) 6. Using Mannings equation:? a) What was the velocity? Show your work. (3pts) b) Using your answer from 6a, what was the discharge? Q = AV Show your work. (2pts) c). Using your answer from 6b, calculate the daily volume of water that flows through this river. Show your work. (1pt) 7. What are the effects of floods on the stream compared to average flows on erosion and moving sediment? (1pt) 8. If this same stream should enter a broader channel with the same discharge (Q), what would happen to the velocity? (1pt) United States Geologic Survey (USGS) The USGS collects information that helps us understand the nation’s water resources and provides discharge records from its gauging stations on the internet. Each dot on the map (Figure 1) represents one USGS stream gaging station. Figure 1: Map of Current Streamflow locations for March 12, 2020 Source: USGS.gov. https://waterwatch.usgs.gov/index.php?id=ww_current A gage station is a facility used by hydrologists and other scientists to monitor streams, wells, rivers, lakes, and other water areas (Figures 2 & 3). The data collected by the station include water height, discharge, chemistry, water quality, temperature and weather conditions such as precipitation, wind speed, and air temperature (USGS.gov, 2020). This data is communicated via satellite and processed and delivered to the public via the USGS website/internet. Figure 2: Schematic of a stream gage. Figure 3: Stream gage along river Source: https://www.usgs.gov/media/images/usgs-streamgage-diagram Source: (Credit: Jeff Conaway, USGS, Alaska Science Center. Public domain.) The water that flows in a river or stream system depends on recent weather patterns and also on the character of the drainage basin in terms of its size, vegetation, rock and soil types, and land-use history (Petersen et al., 2015, 371-72). Over time, river and stream systems can experience water flow that exceeds the ability where the channel system can contain it. Eventually when this capacity is reached, flooding to the adjacent areas can occur. Stream discharge is the amount of water that passes through a cross-section of a stream channel in a specific amount of time and is measured as cfs (cubic feet per second) or cms (cubic meters per second). For further readings on the importance of USGS stream gages, go to https://www.usgs.gov/faqs/how-do-we-benefit-usgs-streamgages?qt-news_science_products=0#qtnews_science_products The UGSG website provides access to water data, various publications, maps, and recent water projects and events. The link to this website is: https://www.usgs.gov/centers/okiwater/data-tools. Your task is to go to the USGS website and gather daily mean (average) values of surface stream flow in (ft3/s) for a river in Ohio in graphical form for this week (Tuesday through Saturday). Instructions are provided on the next page to access the data and graphs. Go to this website: https://www.usgs.gov/centers/oki-water/data-tools. Click on the link titled, “streamflow” under real-time data for Ohio. You will find current streamflow conditions for Ohio. Scroll down to: USGS 03092460 West Branch Mahoning River at Wayland OH As you scroll down, you will be able to select the parameters of gage height, discharge, and precipitation. You will also be able to select the begin date and end date. Once you select the dates, hit the go button. Your task is to cut and paste the three graphs for the study period of 5 days (Tuesday to Saturday) into the word document. If needed, copy and paste instructions are given below. Right click on the graph and you can copy image. Right click on the mouse on your word document and hit paste. Your task is to relate and explain all three graphs together. See example below: Graph #1: Gage in height and feet Take note of the spike of the gage in feet on March 23, 2011 Graph #2: Discharge Graph #3: Precipitation Take note of the precipitation in inches that fell on this site on March 23, 2011. This affected the discharge and height of the water level on that day. 9. a. Graphs cut and pasted onto a word document: __________________ (2pts)? b. What is the county that this site is located in? ___________________ (.5 pt) c. What is the latitude and longitude coordinates? __________________ (.5 pt) 10. Did precipitation fall within the study period and if so, how did it affect the water level and discharge? If no precipitation fell during the study period, what happened to the water level and discharge? (2pts)  I want to look at the step that was taken to get the answer Earth Science Science Geography GEOG 21062 Share QuestionEmailCopy link Comments (0)