UNIT 7 RIVERS AND STREAMS (Chapter 12 Running Water) Study Guide

Transcription

1 UNIT 7 RIVERS AND STREAMS (Chapter 12 Running Water) Study Guide (Revised 7/16) UNIT 7 HOMEWORK worth 10 points WEB HIT: WORK ON RIVER RESEARCH PAPER HOMEWORK see page 11/12 For any Unit Web Hits, go to the DMC HOME website; in Search box type Geology, select Vernon Kramer, scroll down to GEOL 1303, select Syllabus, select Web Hit Links, click on icon of interest for web sites OR: go to DMC Home website, select Degrees, Certificates, Courses, scroll down to Natural Sciences and select Geology, select Faculty Listings, select Walter Vernon Kramer, find Geol 1303, select Syllabus, and there you can find the web hit links click on icon of interest for web sites [IF NONE OF THE WEB SITES COME UP, YOUR COMPUTER PROBABLY NEEDS TO BE REBOOTED (RESTARTED) SEE PAGES 12 & 13 FOR RIVER RESEARCH PAPER General - Landscapes without a hydrologic system will change very little over time. For example, the Moon surface has changed very little over the last billion years. Erosion: the removal of rocks and soil by ground water, running water, waves, glaciers or wind - There are many large river channels that have deeply cut the surface of Mars. Surprisingly, the water that cut these channels did not come from rainfall, but from groundwater. - Recent satellite pictures show channels that were carved by rivers of liquid methane on the Saturn moon of Titan. Thus we know of river channels on two planets and one moon. - River and stream valleys dominate the appearance of the Earth s surface as impact craters dominate the lunar surface. Erosion River erosion: surface removal and transport of rocks and soils by flowing water - River and stream valleys dominate the appearance of the Earth s surface as impact craters dominate the lunar surface. - There are more than 11,240 rivers in Texas alone that cause erosion and shape our landscape! Truth is stranger than fiction, but it is because fiction is obliged to stick to possibilities; truth isn t. Mark Twain Landforms Can be Created by Rivers - Landforms (hills and valleys) shaped by running water (rivers) produce the most significant erosional landforms on Earth. The Grand Canyon is a prime example of this. - River networks can even dominate landscapes in both humid and desert environments. Water Supply - Rivers and lakes provide 50% - 60% of the US public water supply, even though rivers and lakes contain about 2%-3% of Earth s water. - Some have suggested that the creation of millions of large and small lakes has prevented a rise in sea level. These lakes are preventing the water from returning to the oceans. Basic River Components - What is a river? Any large body of water that flows downhill in a well-defined channel (water that flows under gravity to progressively lower levels). 1

2 Headwaters: The source area for the beginning point of rivers and streams. River bed or river channel: An elongated depression or passageway containing (or had contained) flowing water. River banks: The ground bordering both sides of a river that serves to confine the water to the natural channel during its normal course of water flow. Tributary: A stream or smaller river that joins a larger river. This larger river can be a tributary if it joins an even larger river. River mouth: The final point of water discharge for a river (usually where a delta forms). River system: a river channel and all its tributaries GENERAL CHARACTERISTICS OF A RIVER SYSTEM (Remember the Gonsalves painting that compares river drainage systems to a large tree with many branches) - Again: a tributary is a smaller river that joins a larger river 1) The number of tributaries decreases downstream. (Like the number of branches that decrease as you go down from the very top of the tree) 2) Tributary length increases downstream. (Individual tree branches get longer as you go down the top of the tree.) 3) The river gradient (steepness) generally decreases downstream. (Water runs downhill.) 4) River channels are wider and deeper downstream. (Just like tree branches get bigger as you go down from the top of the tree.) 5) Valley size is proportional to river size and increases downstream. Generally - larger the river, the larger the river valley. The tragedy of life doesn't lie in not reaching your goal. The tragedy lies in having no goals to reach. Benjamin Mays 2

3 Reported Speeds of River Flow 1. River Discharge velocity: The calculated volume of water of a river as it moves past a specified line per unit of time (i.e. 4,000 cubic feet of water/second). - A common number reported by TV news reporters during times of floods. 2. River water velocity (in the US commonly reported as feet/sec) within a river channel 3. The steeper the river gradient (from high elevation to low elevation), the faster the water will flow The surest way not to fail is to determine to succeed. Richard B. Sheridan Relative Water Speeds of Various Types of Channels Straight River Channel verses Curved River Channels Velocities: In any channel, moving water speed is affected by friction on the sides and the bottom of the channel - Even the surface air presents a weak friction force on the river s surface to slow down the water movement. - Straight river channel: a) Slower water velocity rate: is found along the river bottom, along river edges (banks) and along the top of the water (air surface) b) The fastest water velocity rate is found at the center of the river channel, slightly below the surface; water velocities in straight and curved channels; darker is faster - Curved river channel: When the water of a river enters a curved river channel, centrifugal forces take over and the water mass begins to rotate. a) Slower water velocity rates are found on the inside of a curve; here sand will be deposited as sand bars. This also presents a shallow river area that is safer to play and wade. b) Faster water velocity rates are found toward the outside of curves; here erosion occurs by undercutting the banks (cut-banks). This is a dangerous area to swim because the water speed could sweep you under the eroding river banks. Channel Components Along the River - Most natural rivers do not flow very far in a straight line; river channels are noted by their curvedshaped patterns. Whenever you see very straight, long river channel it was probably man who prepared these channels. Meanders: Broad, looping bends in a river that can form a sinuous (winding) pattern Cut banks: A river bank eroded on the outside curve of a river channel meander 3

4 Point bars: A crescent-shaped accumulation of sand and gravel deposited on the inside of a river channel meander Natural levees: A broad, low embankment built up along the banks of a river channel during floods Oxbow lakes: A temporary lake formed in the channel of an abandoned meandering river or stream - The creation of oxbow lakes can cause land ownership problems if the title uses the river channel as a property boundary instead of using surveyed points. The formation of oxbow lakes can also create problems for state and international boundaries that use only the river bank for a boundary instead of surveyed points. River sketch: cut banks, point bars, meanders, oxbow lakes We must be vigilant in our quest to prevent the death of consequences such as: -You find it acceptable to fail a class and don t feel that you wasted your time and money River Systems and Drainage Basins River system consists of a main channel and all its tributaries all within a single drainage basin. - Any water (precipitation as rain or snow) that falls within a certain drainage basin is confined to that river system or drainage basin. 4

5 Drainage basins of Texas Drainage Divides Drainage Divide: A boundary that separates one drainage basin (river system) from another - Water from rainfall within one drainage basin (watershed) will not enter another drainage basin (watershed). US Continental Divide Continental Divide Continental Divide: The main divide (an imaginary line) of any continent that separates rivers that empty into different ocean basins US Continental Divide: The US continental divide runs along the crest of the Rocky Mts. from Canada to Mexico, and divides the US into two large drainage basins. - The US Continental Divide separates the rivers; one set of rivers drains water westward to the Pacific Ocean and the other set of rivers drains water to the east and southward to the GOM and the Atlantic Ocean. River Systems - General River Systems may be divided into three subsystems with gradational boundaries: 1. Erosion Subsystem - mostly eroding sediments at headwaters of rivers 2. Transporting Subsystem mostly transporting eroded sediments along the rivers 3. Deposition Subsystem mostly deposition of sediments at the end of a river system 5

6 1. EROSION SUBSYSTEM rivers as agents of erosion of rocks and sediments - A network of headwater tributaries that funnels water and eroded sediments into a larger channel - River systems commonly form a dendritic (tree-like) drainage patterns that extend upslope to the eroding edge of the drainage basin. - We have found dendritic drainage patterns on Mars and the moon Titan - Dendritic channels and valleys generally have V-shaped valleys. - There are other types of drainage patterns, but these patterns are not very extensive. - Typically, headwaters have clearer stream or river waters like we find in the upper Frio River. - River erosion processes on Earth operate at a faster pace in areas that have large, major river systems (more water available). - Erosion will proceed at a much slower pace within areas with minor river systems such as within deserts (less water available). Rivers Erosional Processes Changing Landscape - There are three processes that a river system uses to erode and change the landscape A. Removal of regolith (regolith is loose soil and rock on top of solid rock) - Regolith can be washed or can slide into a river channel and can be removed from the area B. Downcutting of the river channel (which broadens and deepens the river valley) C. Headward erosion uses several processes to expands the drainage basin A. Removal of Regolith - The loose regolith will be washed down slope (hydraulic action) and transported down slope into the river channels. B. Downcutting of River Channels by Abrasion Abrasion: In swift moving water, colliding individual rocks and sand will grind out of the bottom and sides of the river channel - In swift moving rivers, you can often hear the noise made by the grinding action Down-cutting of river channels by abrasion occurs mostly during floods results in deeper channels Incised channel river channel cut into solid rocks (which form canyons) 6

7 Pothole: Cone-shaped hole or depression formed in a river bed by swirling and grinding action of individual rocks and gravel. - These resemble grinding bowls produced by earlier Native Americans. C. Headward Erosion Headward Erosion - Upriver Migration of Waterfalls - Erosion and down-cutting of waterfall ledges can cause these rocky ledges to locally collapse. This results in a new waterfall ledge. With this process, we can witness the head-ward (upriver) migration of a waterfall over time, as exemplified by the ever-moving location of Niagara Falls. Headward Erosion Extending Drainage Basin - Erosion that can extend the reach of a drainage basin Headward Erosion River Piracy Stream Piracy: The diversion of the waters of one stream into another stream (modifies and changes the drainage basin of more than one river). - The Pecos River system of West Texas provides a good example of stream or river piracy. As the Pecos River eroded head-ward, it encountered other river channels. Because the Pecos River channel had a lower elevation than the river it encountered, the captured channel water was diverted into the Pecos. Then 3-D Presentation of Eroding Canyons We must be vigilant in our quest to prevent the death of consequences, such as: -You take money from grants, parents, scholarships and feel it is acceptable to earn less than an A and it is acceptable to later quit your education 2. TRANSPORTING SUBSYSTEM - rivers as agents for transporting rocks and sediments - River channels through which water and sediment flows from the eroding area toward an ocean or a basin. - Depending upon sediment size and location, it may take thousands of years or longer to move from its eroded site to a transporting river - Rivers associated with transporting systems generally have U-shaped valleys. 7

8 - Erosion and deposition both occur but are generally balanced in a transporting subsystem. Sediment Load: rocks and soil, etc. that is carried along by the water movement A) Suspended load involves fine particles (such as mud) carried at same rate as the water velocity. This load represents the largest fraction of transported sediment that will be deposited within oceans, lakes, or basins. B) Bed load represents coarse particles (such as sand and gravel) that is moved along the river bed by rolling, etc.; the water velocity controls the grain size of the bed load; during floods bed loads can represent 50% of the total sediment load C) Dissolved load: dissolved minerals, acids, ions, gas, and pollutants from areas of heavy vegetation, shale and igneous rocks; in jungles and swamps is represented by dark-colored river waters FYI: usually involves 4 cations [Ca +2, Na +1, Mg +2, K +1 ] and 3 anions [HCO3-1, SO4-1, Cl -1 ]. Dams Affecting Sediment Transportation - Dams also can severely impact river systems and people; sometimes in a very negative way by upsetting biologic cycles and sediment cycles that prevent sediment from maintaining and expanding deltas. 3. DEPOSITIONAL SUBSYSTEM - rivers as agents for depositing rocks and sediments - The dispersion of the sediments from the river is a deposition system i.e. the sediment load is dropped to fill in a basin, which is generally an ocean basin. - Rivers with the largest active deposition of sediments into the oceans: Ganges River, Amazon River, Mississippi River. 8

9 Deposition within an Erosion Subsystem (filling a non-ocean basin) - Not all sediment reaches an oceanic basin Alluvial fan: Accumulation of sediment in a dry basin. The sediment will form fan-shaped deposits especially in dry, mountainous areas. 9 Alluvial fan sketch Deposition in the Transporting Subsystem (filling a non-ocean basin) Alluvium: Any sediment deposited by the recent action of rivers (most sediment is deposited by floods) Floodplain: The flat, occasionally flooded area that borders a river or stream (filled with alluvium) The Depositional Subsystem Delta: a low, nearly flat alluvial area near the mouth of a river, formed by sudden drop in water velocity and dumping of its sediment load - There are many types of delta classifications - The Mississippi River delta is classified as a bird-foot delta because of its unique shape - Large swamps are an integral part of most deltas. Delta Creation Deltas evolve by 2 mechanisms: 1) Distributary Channels, 2) Avulsion 1. Distributary Channel: numerous stream channels in a delta that disperse water and sediment 2. Avulsion: This represents a shift in the main course of a river to a totally new and different channel that results in forming a new delta in a new location. Flooding - Floodplain stages: 1) Normal stage: river water level that is below its bank or natural levee 2) Bank-full stage: river water level that stays about even with its banks or levee 3) Flood stage: the water in the river that overflows its river banks and the water submerges the local area (flooding) We must be vigilant in our quest to prevent the death of consequences such as: -You convince yourself that it is ok to fail exams and that you don t have to change your study methods

10 Floods Floods: Rivers overflowing their natural levee. Floods are not a rare event but a seasonal occurrence. - Floods have possibly been the cause of the greatest natural loss of human life in recorded history. Flash Flood: A local and sudden flood of short duration caused by a local large downburst of rain. Flash floods often occur in valleys in a semi-arid regions and hilly terrain but can also occur in cities (because of all of the pavement and poor drainage planning). These floods can wash vehicles and people downstream or flood roads and streets and underpasses. Some River Generalities - In Texas, any stream bed wider than 30 feet is public property, regardless if it has flowing water or is a dry bed. These stream beds are legally navigable streams. - In January2004, it became illegal in Texas to drive off road vehicles in river beds. - Nueces Drainage Basin includes the Nueces River, Frio River, Atascosa River and many smaller tributaries. - There are two large reservoirs, created by dams, within the Nueces watershed: Choke Canyon Lake (near Three Rivers) and Lake Corpus Christi (near Mathis). - Lake Texana is located near Edna, TX on the Navidad River. This reservoir provides almost 50% of the drinking water for Corpus Christi via the 101 mile long Mary Rhodes pipeline. ALWAYS ON EXAM - There is a salt water barrier dam on the Nueces River at Labonte Park to prevent high tides (salt water) from entering the upper reaches of the river system and contaminating our water supply. The squeaky axle gets the grease 10

11 LOCAL RIVERS TEAM DISCOVERY PROJECT FOR UNIT #7 RIVER SYSTEMS (Designed for Written Communication Skills and Critical Thinking Skills Guadalupe, San Antonio, Nueces River Basins Frio River Basin (Tributary of Nueces River) Purpose: Prepare a tri-folded travel brochure or tour guide for your selected local Texas river ITEM #1; Each team member must select one of the four (4) possible choices of rivers for a brochure River Choices: (Only one river each student in a group of 4 thus each group will have 4 different rivers) 1) Guadalupe River; 2) San Antonio River (tributary to the Guadalupe River); 3) Nueces River; 4) Frio River (tributary to Nueces River) References to List: at least 3 (list only references used) and include your name at END of brochure You can create a black and white or colored TRAVEL BROCHURE with a map of the river and interesting pictures of river features. Do not copy a brochure from the internet called plagiarism, as I will check! Get your pictures from the internet or use your own pictures. Some features that you may want to point out could include: (up to you which to use): a) location source of the river b) location of estuary into which it empties or main river that intercepts this river (if a tributary) c) length of the river; d) maybe list a few major towns along its banks; e) maybe mention dams or lakes along its course; f) maybe list names of public State parks and a few public campgrounds along its course; g) maybe popular sports/recreation centers along its course; h) maybe special species of fish, animals, plants found along its course; i) maybe any special information that you found interesting about the river For your team members: Print out completed copies for each one; REMEMBER THE DUE DATE See following page 12 for grading rubrics 11

12 GRADING RUBRICS for RIVER RESEARCH PROJECT COMMUNICATIONS SKILLS-(for RIVER RESEARCH PROJECT) Rubric for Aspect 1 Written communication: 6 points Exceeds Expectations 5 points Meets Expectations 2 points Below Expectations 0 Not Acceptable Message appropriate for purpose, Exceptionally appropriate/effective for purpose, occasion Content adequately appropriate/effective for purpose, Content inadequate for purpose, Failed to meet assignment purpose Clear & coherent organizational structure Main points fully supported ( 10 examples, figures, etc.) Referenced web sites Exceptionally clear organization pattern; easily followed Multiple examples, memorable details that support central theme Reasonably organized; logical progression of ideas Adequate details and 10 examples, to support central theme Rambled; organization difficult to follow; lacked unity Lacked adequate number of examples to support central theme More than 3 websites Referenced 3 websites Referenced 2 websites Repetitive ideas; impossible to follow No details provided or failed to support central theme No websites referenced or listed references they did not use Aspect 6 Synthesis: Integrate/organize information in its functional context CRITICAL THINKING SKILLS (for RIVER RESEARCH PROJECT) Rubric for Aspect 6-2 Exceeds 1 Meets 0 Below 0 Not Acceptable Information is clearly organized & integrated into a functional context Some information is organized and integrated into a functional context Information is organized but not integrated into a functional context Ideas are disjointed and presented without a contextual framework If you use Microsoft Office and Word: Open Word Document Click File Click New Depending upon version of Office: Select Brochures and Booklets or Tri-fold brochure (remember to use front and back sides) 12