Lab 4 Community Structure Plants, Lab 5 Stream Morphology

Stream Morphology Investigation Manual

ENVIRONMENTAL SCIENCE

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STREAM MORPHOLOGY

Overview Students will construct a physical scale model of a stream system to help understand how streams and rivers shape the solid earth (i.e., the landscape). Students will perform several experiments to determine stream flow properties under different conditions. They will then use the scientific method to test their own scenario to understand how the geological landscape is altered by this system.

Outcomes • Design a stream table model to analyze the different

characteristics of stream flow. • Explain the effects of watersheds on the surrounding

environment in terms of the biology, water quality, and economic importance of streams.

• Identify different stream features based on their geological formation due to erosion and deposition.

Time Requirements Preparation ....................................................................... 5 minutes

(let sit overnight) Activity 1: Creating a Stream Table ................................ 60 minutes Activity 2: Scientific Method: Build Your Own

Stream Table .................................................. 45 minutes

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Key Personal protective equipment (PPE)

goggles gloves apron follow link to video

photograph results and

submit

stopwatch required

warning corrosion flammable toxic environment health hazard

Key Personal protective equipment (PPE)

goggles gloves apron follow link to video

photograph results and

submit

stopwatch required

warning corrosion flammable toxic environment health hazard

Table of Contents

2 Overview 2 Outcomes 2 Time Requirements 3 Background 7 Materials 8 Safety 8 Preparation 8 Activity 1 9 Activity 2 10 Disposal and Cleanup 10 Data Tables 11 Observations

Background A watershed is an area of land that drains any form of precipitation into the earth’s water bodies. Whether it is rain flowing into a lake, or snow soaking into the groundwater, the entire land area that forms this connection of atmo- spheric water to the water on Earth is consid- ered a watershed.

Water covers approximately 70% of the earth’s surface. However, approximately two-thirds of all water is impaired to some degree, with less than 1% being accessible, consumable fresh- water. Keeping watersheds pristine is the leading method for providing clean drinking water to communities, and it is a high priority worldwide. However, with increased development and people flocking towards waterfront regions to live, downstream communities are becoming increasingly polluted every day.

From small streams to large rivers (hereafter considered “streams”), stream flow is a vital part of understanding the formation of water and landmasses within a watershed. Understanding the flow of a stream can help to determine when and how much water reaches other areas of a watershed. For example, one of the leading causes of pollution in most waterways across the United States is excessive nutrient and sediment overloading from runoff from the land- masses surrounding these waterways. Nutrients such as phosphorus and nitrogen are preva- lent in fertilizers that wash off lawns and farms into surrounding sewer and water systems. This process can cause the overproduction of algae, which are further degraded by bacteria. These bacteria then take up the surrounding oxygen for respiration and kill multiple plants and organisms. A comprehensive understanding

of the interaction between streams and the land as they move downstream to other areas of a watershed can help us to prevent pollution. One example of this is to build a buffer, which is a group of plants that can be grown along parts of the stream bank that are more susceptible to pollution and can absorb excessive nutrients; this therefore lessens the effects of nutrient overloading in the streambed.

Sediment, which is easily moved by bodies of water, has a negative effect on water quality. It can clog fish gills and cause suffocation, and the water quality can be impaired by becoming very cloudy because of high sediment flow. This can create problems for natural vegeta- tion growth because of the obstruction of light and prevent animals from visibly finding their prey. Erosion also has considerable effects on stream health. Erosion, or the removal of mate- rial (soil, rock, or sand) from the earth to another location, is caused by actions such as physical and chemical weathering. These two processes loosen rocks and other materials, and can move these sediments to other locations through bodies of water. Once these particles reach their final destination, they are considered to be deposited. Deposition is also an important process because where the sediment particles end up can greatly impact the shape of the land and how water is distributed throughout the system. Erosion and deposition can occur multiple times along the length of a stream and can vary because of extreme weather such as flooding or high-wind events. Over time, these two processes can completely reshape an area, causing the topography, or the physical features, of an entire watershed to be altered. Depending

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STREAM MORPHOLOGY

Background continued on weather conditions, a streambed can be altered very quickly. Faster-moving water tends to erode more sediment than it deposits sedi- ment. Deposition usually occurs in slower- moving water. With less force acting on the sedi- ment, it falls out of suspension and builds up on the bottom or sides of the streambed.

Sediments are deposited throughout the length of a stream as bars, generally in the middle of a channel, or as floodplains, which are more ridgelike areas of land along the edges of the stream. Bars are generally made of gravel or sand-sized particles, whereas floodplains are made of more fine-grained material. Deltas and alluvial fans are sediment deposits that occur because of flowing water and are considered more permanent structures because of their longevity. They are both fan-shaped accumu- lations of sediment that form when the stream shape changes. Deltas form in continuous, flowing water at the mouth of streams, whereas alluvial fans only form in streams that flow inter- mittently (when it rains or when snow melts). Alluvial fans are usually composed of larger particles and will form in canyons and valleys as water accumulates in these regions. The fan shape of both deposits is easy to spot from a distance, as they are formed due to the sand settling out on the bottom of the streams.

Stream Flow Characteristics Discharge, or the amount of water that flows past a given location of a stream (per second), is a very important characteristic of stream flow. Discharge and velocity (the speed of the water moving in the stream), are both vital to the shaping of streambeds. Within stream ecosystems, there are microhabitats (smaller

habitats making up larger habitats) that have different discharges and velocities. The type of microhabitat depends on the width of that part of the stream, the shape of the streambed, and many other physical factors. In areas that contain riffles, water quickly splashes over shallow, rocky areas, which are easily observed in sunny areas (See Figure 1). Deeper pools of slower-moving water also form on the outside of the bends of the streams, as shown in Figure 1. Runs, which are deeper than riffles but have a moderate current, connect riffles and pools throughout the stream. The source of a stream is where it begins, while the mouth of a stream is where it discharges into a lake or the ocean.

Flow rate is very helpful for engineers and scien- tists who study the impacts of a stream on organisms, surrounding land, and even recre- ational uses such as boating and fishing. The

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Figure 1.

Riffles Pool

speed of the water in specific areas helps deter- mine the composition of the substrate in that area of the streambed, i.e., whether the material is more clay, sand, mud, or gravel; particle sizes of different sediments are shaped and deposited throughout various areas of a stream, depending on these factors.

Most streams have specific physical features that show periodicity or consistency in regular intervals. Meanders can occur in a streambed because of gravity. Water erodes sediment to the outside of a stream and deposits sediment along the opposite bank, forming a natural weaving or “snaking” pattern. This pattern can form in any depth of water and along any type of terrain. Sinuosity is the measure of how “curvy” a stream is. This is a helpful measurement when determining the flow rates of streams because it can show how the curves affect the water velocity. In major rivers and very broad valleys, meanders can be separated from the main body of a river, leaving a U-shaped water body known as an oxbow lake.

Another feature important for stream flow is the difference in elevation, or the relief of a stream as it flows downstream. Streams start at a higher elevation than where they end. This causes the discharge and velocity at the source versus that at the mouth of the stream to be quite different, depending on the meandering of the stream and the type of deposition and erosion that is occur- ring. The gradient is another important factor of stream morphology. This is a measure of the slope of the river over a particular distance (the relief over the total distance of the river). For a kayaker who wants to know how fast he can travel down a particular river, knowing the

difference in elevation (relief) is important over a particular area; however, knowing the slope of this area will give him a more accurate predic- tion. With erosion and deposition occurring at different rates and at different parts of the stream, knowing the gradient is a very important part of determining stream flow for the kayaker.

Groundwater is also affected by changes in the stream shape and flow. Water infiltrates the ground in recharge zones. If streams are contin- uously flowing over these areas, the ground is able to stay saturated. Most streams are perennial, meaning they flow all year. However, a drought or an extreme event may lower the stream level. This can lower the groundwater level, which then allows the stream to only sustain flow when it rises to a level above the water table. With the small amount of available freshwater on Earth, it is vital that our ground- water sources stay pristine.

Biotic and Economic Impacts of Streams Not only are streams a major source of clean freshwater for humans, they are also a hotspot for diversity and life. There is great biotic vari- ability between the different microhabitats (e.g., riffles, pools, and runs) of a stream. Riffles, in particular, have a high biodiversity because of the periodicity of the water. Pools usually have fewer and more hardy organisms in their slower, deeper moving waters. There are also a multi- tude of plant and animal species living around streams. From a stream in a backyard to the 1500-mile-long Colorado River, thousands of types of birds, insects, and plants live near these water bodies because they are nutrient-rich with clean freshwater. Sometimes nutrient spiraling

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STREAM MORPHOLOGY

Background continued can occur in these streams. Nutrient spiraling is the periodic chemical cycling of nutrients throughout different depths of the streams. This process recycles nutrients and allows life to thrive at all depths and regions of different-sized streams.

Many state and local governments maintain local waterway health by recruiting local volun- teers who test the quality of the streams in their communities. Simple water chemistry tests and basic macroinvertebrate identification can yield a lot of information about the health of a stream. Macroinvertebrates are small aquatic fauna found in streams. They are comprised of different worms, mollusks, arthropods, and bugs that can be caught in small nets. In addition to visual cues, identifying the types of organ- isms that live within different microhabitats of a stream and determining a few chemical factors can help scientists decide which streams are impaired and why.

Streams can also have significant economic impacts on a region. Streams are a channel for fishing and transportation, two of the largest industries in the world. Due to all the commer- cial boating operations that occur worldwide in these channels, it is vital to understand the formation and flow patterns of the streams so that they are clear and navigable. Fishing for human consumption is another large, worldwide industry that depends on stream health; keeping streams pristine and understanding how they form are of utmost importance in sustaining this top food industry. Recreational activities such as kayaking, sport fishing, and boating all shape areas where streams and rivers are prevalent as well.

All acts that happen on land affect the water quality downstream. When creating a model stream table in this lab, large, system-wide effects can be predicted. Many land features and physical parts of a streambed can affect the flow of water within a watershed. Houses along a streambed or numerous large rocks can cause the stream flow to change directions. If any of these factors cause erosion or deposition in an area of the stream, microhabitats can be created; these factors can affect the stream on a larger scale, creating changes in flow speeds and widths of the streambeds.

The Importance of Scaling and the Use of the Scientific Method When a stream table model is created, a large- scale depiction of a streambed is being reduced to a smaller scale so that the effects of different stream properties on the surrounding envi- ronment can be modeled. While the stream table made in this lab is not a “to-size” stream and landscape, the same processes can be more easily observed at a scaled-down size. Scientists frequently create models to simplify complex processes for easier understanding. For example, to physically observe something that is too big, such as how far each planet in the solar system is from one another, the spatial distance can be scaled to create a solar system model. By changing the distance between each planet (from kilometers to centimeters), this large system is now more feasibly observed. Similarly, the stream model allows us to physically view different scenarios of a streambed and analyze different stream properties. Mathematical equa- tions are also used frequently to observe data in order to predict future conditions, such as in

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meteorological models. Ultimately, models are a very important key for predicting future events and analyzing processes that occur in a system.

When creating a model, many different outcomes for the same type of setup are possible. In this investigation, multiple variations of similar-sized streambeds will be designed so that we are able to evaluate different stream features and their impacts on the surrounding ecosystem. When performing any type of scien- tific evaluation, the scientific method is very useful in obtaining accurate results. This method involves performing experiments and recording observations to answer a question of interest.

When creating stream table models, we are trying to understand how different factors can affect stream flow. A few very important steps are required. The first step is forming a test- able hypothesis, or an educated prediction, of what one expects to observe on the basis of previous knowledge of the subject. In Activity 1, the steps are already listed, so the main goal is to compare the two differences in stream reliefs. However, in Activity 2, the goal is to alter a different variable and predict what will happen to several stream features in this new situation. When recording these observations to test a hypothesis, it is important to repeat the tests. To obtain valid results, you need to have similar results over multiple attempts to ensure consis- tency in the findings and to show that what you are discovering is not by chance, but instead replicated each time the experiment is run.

Materials Included in the materials kit:

Included in the equipment kit:

Sand, 3 lb

Plastic cup

Foam cupFoam tray

RulerPaper clip

Reorder Information: Replacement supplies for the Stream Morphology investigation can be ordered from Carolina Biological Supply Company, item number 580819.

Call: 800.334.5551 to order.

Needed but not supplied: • 2 Books, one approximately 2-cm thick and

the other 4-cm thick • Tap water • 2 Plastic bags (to cover the books or objects

you don’t want getting wet) • Stopwatch (or cell phone with a timer)

STREAM MORPHOLOGY

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Safety Read all the instructions for this laboratory activity before beginning. Follow the instruc- tions closely and observe established labo- ratory safety practices, including the use of appropriate personal protective equipment (PPE) described in the Safety and Procedure sections.

Do not eat, drink, or chew gum while performing this activity. Wash your hands with soap and water before and after performing the activity. Clean the work area with soap and water after completing the investigation. Keep pets and children away from lab materials and equipment.

Preparation

1. Read through the activities. 2. Obtain all materials. 3. Pour the sand in an even layer on the yellow

foam tray. 4. Pour water slowly over the sand until it is

completely saturated. Pour off any excess water outside.

5. With your hands, rub the sand flat and let the sand dry overnight in the foam tray.

6. Using a paper clip, poke a hole in the side of the foam cup, 1 cm up from the bottom of the cup.

Note: This investigation is best performed outdoors or in an area where it is easy to clean wet sand and water. DO NOT dump any of the sand and water mixture down the sink, as it can cause clogging.

ACTIVITY 1

ACTIVITY

A Creating a Stream Table 1. Bring the tray outside and place the

4-cm-thick book in a plastic bag. Place the book under one end of the foam tray so that it is tilted, as shown in Figure 2.

2. Fill the plastic cup with tap water and slowly pour the water into the foam cup. Ensure that the cup is right above the higher end of the tray. Note: Store extra tap water on-site if more water is needed to form a stream.

3. Let the water trickle out of the hole in the cup down the sand. Observe how the water forms a stream in the table. Stop pouring after a small stream flow has formed down the table.

4. In the Observations section, draw what the formed stream looks like. Label where erosion and deposition occur along the streambed. In addition, take a photograph of the stream.

5. Use the instructions below to calculate the values for the different physical stream features and record these values in Data Table 1.

Measure the width and depth at the mouth of the stream to calculate the cross-sectional area.

a. Sinuosity = Curvy distance (cm)/Straight distance (cm) (no units) i. Use a ruler to measure the distance

Figure 2.

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Gently pour the excess water from the stream table into the grass and flatten the sand out where the stream formed, making a uniform layer.

6. Repeat Steps 2–6 to complete 2 more trials. 7. Repeat Steps 2–7 with the 2-cm-thick book

to obtain a more gradual stream formation.

ACTIVITY 2

A Scientific Method: Build Your Own Stream Table

1. Design a procedure similar to Activity 1. Choose one height to test the trials and change a different variable to analyze the same calculations for stream movement and formation throughout the streambed.

2. Form a hypothesis for what will happen to the various calculations and test it by using the same procedure as in Activity 1. Activities such as pre-digging a stream, adding a “dam” or other features along the streambed, changing the inflow of the water from the foam cup, or adding plants along these areas are all common factors that can be altered within a streambed.

3. Perform 3 trials of your experiment and record your results in Data Table 2.

from the mouth to the source of the stream along the curve (curvy distance).

ii. Use a ruler to measure the distance straight down the stream from the mouth to the source of the stream (straight distance).

iii. Now, divide the two distances. Note: If there is no curvy distance, then the sinuosity is 1.

b. Velocity = Distance traveled (cm)/Time for travel (s) (recorded in cm/s) Rip off a small piece of foam from the top of the foam cup. Using a stopwatch, time (in seconds) how long it takes the foam to float downstream. Divide the curvy distance by this time.

c. Discharge = Velocity (cm/s) x Cross-sectional area (cm2) (recorded in cm3/s)

Cross-sectional area: Width of the stream (cm) x Depth of the stream (cm)

d. Relief = Highest elevation (cm) − Lowest elevation (cm) (recorded in cm) Measure the elevation change from the beginning to the end of the stream. Use the ruler to measure the highest point of the incline to the ground for the highest elevation and measure the bottom part of the tray to the ground for the lowest elevation.

e. Gradient = Relief (cm)/Total distance (cm) (recorded in cm) Measures the slope of the stream; divide the relief by the total distance (If the stream is curvy, the “total distance” is the curvy distance; if not, then the total distance is the straight distance).

Note: In Activity 1, the heights of the source of the streams were altered to observe how stream flow and streambed formation were affected. In Activity 2, use your stream flow knowledge to design an experiment (with multiple trials) by altering a different char- acteristic. Record the same calculations for your new experimental setup.

Disposal and Cleanup 1. Dispose of the mixtures either in the

environment or in the household trash. 2. Clean up the areas containing any remnants

of the sand and water mixture and wash your hands.

Data Tables Data Table 1.

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Trial Sinuosity Velocity(cm/s) Discharge

(cm3/s) Relief (cm)

Gradient (cm)

4 cm

1

2

3

2 cm

1

2

3

Data Table 2.

Variable changed:_________________________________________________________________________

Trial Sinuosity Velocity(cm/s) Discharge

(cm3/s) Relief (cm)

Gradient (cm)

1

2

3

ACTIVITY

Observations Activity 1

Activity 2

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ENVIRONMENTAL SCIENCE Stream Morphology Investigation Manual

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