Geography Geomorphology Info & Questions PDF

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You have Downloaded, yet Another Great Resource to assist you with your Studies  Thank You for Supporting SA Exam Papers Your Leading Past Year Exam Paper Resource Portal Visit us @ www.saexampapers.co.za  TABLE OF CONTENTS 1. INTRODUCTION 3 2. HOW TO USE THIS SELF STUDY GUIDE? 4 3. EXAMINATION STRUCTURE 5 4. EXAMINATION TIPS 6 4.1 TYPES OF QUESTIONS 6 4.2 FLASHBACK ON THE WATER CYCLE 8 5. CONCEPTS OF DRAINAGE BASINS 9 A. KEY CONCEPTS AND NOTES 9 B. FACTORS INFLUENCING INFILTRATION OF WATER 10 C. DRAINAGE BASINS ACTIVITIES 11 6. TYPES OF RIVERS 14 A. KEY CONCEPTS 14 B. NOTES AND EXPLANATION 14 C. TYPES OF RIVERS ACTIVITY: 16 7. DRAINAGE PATTERNS 17 A. KEY CONCEPTS 17 B. NOTES AND EXPLANATIONS 17 C. DRAINAGE PATTERNS ACTIVITIES 21 8. DRAINAGE DENSITY 25 A. KEY CONCEPTS 25 B. FACTORS INFLUENCING DRAINAGE DENSITY 26 C. DRAINAGE DENSITY ACTIVITIES 28 9. STREAM ORDERS 30 A. KEY CONCEPTS AND NOTES 30 B. LAWS OF STREAM ORDERS 30 C. ACTIVITY ON MAP WORK APPLICATION OF STREAM ORDERS 31 10. RIVER DISCHARGE 32 A. KEY CONCEPTS AND NOTES 32 B. FLUVIAL PROCESSES 33 11. RIVER PROFILES AND THE STAGES OF A RIVER 34 A. LONGITUDINAL PROFILE AND STAGES OF A RIVER 34 B. CROSS /TRANSVERSE PROFILE: FRONT VIEW OF A RIVER FROM BANK TO 35 BANK 1 12. RIVER GRADING 36 A. KEY CONCEPTS AND NOTES 36 B. BASE LEVELS OF EROSION 37 C. RIVER GRADING ACTIVITIES 38 13. FLUVIAL LANDFORMS IN THE DIFFERENT STAGES OF THE RIVER 40 A. KEY CONCEPTS AND NOTES 40 B. FLUVIAL LANDFORMS AND FEATURES ACTIVITIES 48 14. RIVER REJUVENATION 55 A. KEY CONCEPTS AND NOTES 55 B. RESULTANT LANDFORMS 55 C. RIVER REJUVENATION ACTIVITIES 56 15. RIVER CAPTURE/STREAM PIRACY 58 A. KEY CONCEPTS AND NOTES 58 B. CAUSES AND CHARACTERISTICS 59 C. STREAM PIRACY ACTIVITIES 62 16. SUPERIMPOSED AND ANTECEDENT DRAINAGE PATTERNS 64 A. KEY CONCEPTS AND NOTES 64 C. SUPERIMPOSED AND ANTECENDENT DRAINAGE ACTIVTIES 65 17. CATCHMENT AND RIVER MANAGEMENT 66 A. KEY CONCEPTS AND NOTES 66 B. CAUSES, IMPORTANCE AND IMPACT OF RIVER MANAGEMENT 66 C. CATCHMENT AND RIVER MANAGEMENT ACTIVITIES 69 18. POSSIBLE ANSWERS 72 19. EXAMINATION ACTION VERBS 84 20. REFERENCES 87 21. ACKNOWLEDGEMENTS 88 2 1. INTRODUCTION The declaration of COVID-19 as a global pandemic by the World Health Organisation led to the disruption of effective teaching and learning in many schools in South Africa. The majority of learners in various grades spent less time in class due to the phased-in approach and rotational/ alternate attendance system that was implemented by various provinces. Consequently, the majority of schools were not able to complete all the relevant content designed for specific grades in accordance with the Curriculum and Assessment Policy Statements in most subjects. As part of mitigating against the impact of COVID-19 on the current Grade 12, the Department of Basic Education (DBE) worked in collaboration with subject specialists from various Provincial Education Departments (PEDs) developed this Self-Study Guide. The Study Guide covers those topics, skills and concepts that are located in Grade 12, that are critical to lay the foundation for Grade 12. The main aim is to close the pre-existing content gaps in order to strengthen the mastery of subject knowledge in Grade 12. More importantly, the Study Guide will engender the attitudes in the learners to learning independently while mastering the core cross-cutting concepts. 2. HOW TO USE THIS SELF STUDY GUIDE? This Self-Study Guide only covers the section on Geomorphology. The booklet is designed to explain concepts that seem to be challenging to learners in the Grade 12 exams. The first part focuses on the Exam structure for Paper 1 or Paper 2, followed by explanation of the most common action verbs used in the question paper and how learners should manage their time. The second part focuses on the selected key concepts with their explanatory notes, followed by assessment activities designed from previous examination question papers. The guide also provides relevant answers and guide learners on how to use a mark allocation (on a question) in order to determine the extent of your response. Mapwork has been integrated in all the relevant sections to follow the new exam structure. The guide should be used in conjunction with other resources such as DBE approved textbooks, 2021 Exam Guidelines and Geography CAPS document. 4 3. EXAMINATION STRUCTURE PAPER 1 3.1.1 This is a 3-hour question paper which is written on a SEPARATE DAY from Paper 2. 3.1.2 The mark allocation for this paper is 150. 3.1.3 The question paper consists of two sections, namely SECTION A and SECTION B: SECTION A: Climate and Weather and Geomorphology (Theory) SECTION B: Geographical Skills, Techniques, Application and Interpretation and GIS (Mapwork) 3.1.4 SECTION A consists of TWO questions of 60 marks each. SECTION B consists of ONE question of 30 marks. 3.1.5 All the THREE questions are compulsory. PAPER 2 3.2.1 This is a 3-hour question paper which is written on a separate day from Paper 3.2.2 The mark allocation for this paper is 150. 3.2.3 The question paper consists of two sections, namely SECTION A and SECTION B: SECTION A: Settlement and Economic Geography of South Africa (Theory) SECTION B: Mapwork- Geographical Skills and Techniques (Map work) 3.2.4 SECTION A consists of two questions of 60 marks each and SECTION B consists of one question of 30 marks. 3.2.5 All the three questions are compulsory. 5 4. EXAMINATION TIPS 4.1 TYPES OF QUESTIONS The types of questions in both Paper 1 and Paper 2 are as follows: 4.1.1 Short objective questions: Multiple-choice: o Know what each multiple-choice question is asking. o Read the entire question. o Evaluate each answer to the multiple-choice question. o Eliminate each answer that is clearly wrong. o Select the best answer. o Do not leave any question unanswered. Matching: o Know the definitions/explanations of concepts for each section as you will be required to pair each item with the correct terminology provided. o These questions assess recognition and recall of knowledge acquired. 4.1.2 Data response questions With a data response question, you are required to interpret diagrams, maps, photos, tables, statistics, cartoons, graphs, etc. Data response questions require knowledge, application, analysis, critical thinking and evaluation. Marks for data response questions range from 2-8 marks. 4.1.3 Paragraph-type questions Paragraphs assess communication skills, knowledge, and insight. These questions require critical and analytical thinking. In order to master these questions, learners should: o underline the main topic of the question, o underline the action words or question verbs, o underline the focus areas of the question (note that most paragraph questions might require two aspects or issues that must be discussed/ explained in two equal parts), o write in full sentences to explain answers, and o avoid repetition of facts. 6 An illustration of how to analyse a paragraph question statement: The cost of food will increase because the polluted water will be expensive to purify so that it could be used in agriculture. Farmers will have to buy more chemicals to purify the water. If not, they will have to buy purified water from other service providers at a costly price. This will have a negative impact on production costs in agriculture, leading to increased food prices. Furthermore, polluted water reduces soil fertility which could lead to crop failure. This could lead to food being imported from other countries at very expensive prices in order to prevent food insecurity in the country. Polluted water will be expensive to purify so as to generate hydro-electricity, thereby causing Eskom to inflate electricity prices. Increased production costs will increase electricity costs. Less production of electricity due to river pollution will increase demand and supply, making electricity costs expensive. (4 x 2) (8) 7  4.2 FLASHBACK ON THE WATER CYCLE Water cycles refers to the process whereby water evaporates from the ocean and is transported by wind, in the form of water vapour and clouds to the atmosphere where it falls back to the surface as precipitation. The precipitation flows on the surface as *sheet flow and *channel flow and become part of the drainage basin. * Sheet flow * Channel flow The even flow of water on the surface The flow of water mainly in rivers 8 5. CONCEPTS OF DRAINAGE BASINS A. KEY CONCEPTS AND NOTES CONCEPT DESCRIPTION Drainage Basin This is the area through which a river system flow Catchment Area The collection area of rainwater in lakes, rivers, and reservoirs River System The mainstream and its tributaries Tributary A river or stream flowing into a larger river Confluence The junction of two rivers/streams Watershed High laying area that separates drainage basins Interfluve High laying area that separates tributaries in a drainage basin Source The place where the river begins It is the part of the river, where the river flow into another river, a lake, a River mouth reservoir, a sea, or an ocean Ground water Water underneath the earth surface Through flow It is the lateral flow of water in the soil zone Water table Upper level of ground water Infiltration When water soaks or filters into the soil 9  B. FACTORS INFLUENCING INFILTRATION OF WATER 1. Amount of water already in the ground Saturated soil can hold more water increasing surface flow. Dry soil absorbs more water increasing infiltration. 2. Evaporation rate High evaporation means that there is less water for infiltration. Dry, hot, and windy 3. Gradient of slope Gentle gradient slopes allow more to infiltrate and be retained by the soil. Steep slopes enable water to run-off more easily 4. Nature and Amount of precipitation Heavy showers cause greater run-off and less infiltration. Softer rains allow more infiltration. 5. Density and type of plant cover Sparse (Little) vegetation encourages run-off and allows rapid evaporation. Thick plant cover allows more infiltration. 6. Porosity High porosity results in high permeability, therefore more infiltration. High porosity in soil increases infiltration. A rock or soil is porous when it is able to store water. 7. Permeability Rocks or soil is permeable when it allows water to pass through it. Rock with high permeability and high porosity are known as aquifers. Rock with low permeability and low porosity are known as aquicludes. 8. Soil Moisture Dry soil absorbs more water and reduce stream runoff. This leads to lower drainage density. Infiltration is low in soil that has high moisture content. 10  C. DRAINAGE BASINS ACTIVITIES 5.1 Refer to FIGURE 5.1 which shows fluvial features and give ONE term for each of the statements below. 5.1.1 Water that flows on the surface after it rains 5.1.2 High-lying area that separates two rivers in the same drainage basin 5.1.3 Water found below the earth's surface 5.1.4 River that flows throughout the year 5.1.5 Upper level of ground water 5.1.6 Meeting place of two rivers 5.1.7 Soaking of water into the ground 5.1.8 Movement of water through the soil to rivers (8 x 1) (8) 11 5.2 FIGURE 5.2 illustrates the main features of a drainage basin. Study the diagram to answer the following questions. 5.2.1 Define the term drainage basin. (1 x 2) (2) 5.2.2 Explain the difference between a watershed and an interfluve. (2 x 1) (2) 5.2.3 What major factor influences the type of river that exists? (1 x 2) (2) 5.2.4 How will the urban environment affect the rate at which run off occurs? (1 x 2) (2) 5.2.5 Give TWO reasons for your answer in QUESTION 5.2.4. (2 x 2) (4) 5.2.6 “Due to human activities, the natural balance that exists within a river system has been disturbed and the natural catchment areas have been degraded.” Write a paragraph of approximately EIGHT lines on the negative impact that human activities have on drainage basins. (4 x 2) (8) 12 MAP WORK APPLICATION 5.3 Refer to the extract from a topographic map and answer the questions that follow. 5.3.1 The area at A represents the (river system/drainage basin). (1 x 1) (1) 5.3.2 Differentiate between high lying areas B and C. (2 x 1) (2) 5.3.3 Refer to D (a) In which direction does the mainstream at D flow? (1 x 1) (1) (b) Provide TWO reasons for your answer to QUESTION 5.3.3(a). (2 x 2) (4) 5.3.4 At which point E or F are the chances of flooding higher? Motivate your choice. (1 + 2) (3) 13 6. TYPES OF RIVERS A. KEY CONCEPTS Concept Explanation Permanent Rivers Flows throughout the year Periodic Rivers Flows every year only in the rainy season Episodic Rivers The rivers only flow for a short period of time after heavy rainfall This is a permanent river that originates in a rainy/wet area but Exotic Rivers later flows through a desert B. NOTES AND EXPLANATION PERMANENT RIVERS / PERENNIAL RIVERS Flows throughout the year. The water table intersects the riverbed throughout the year. Usually occur in areas of high rainfall PERIODIC RIVERS / NON-PERENNIAL RIVERS Flows every year only in the rainy season. The water table intersects the riverbed only in the rainy season. 14  EPISODIC RIVERS The rivers only flow for a short period of time after heavy rainfall The water table never intersects the river bed. Very important water source in dry areas These rivers do not necessarily flow every year. EXOTIC RIVERS This is a permanent river that originates in a rainy/wet area but later flows through a desert. The river does not show the climatic characteristics of its surroundings. 15  C. TYPES OF RIVERS ACTIVITY: 6.1 Refer to FIGURE 6.1 and answer the questions that follow. Photograph A shows an episodic river in the north-western part of South Africa. Photograph B shows a permanent river in the same area. 6.1.1 (a) What is an episodic river? (1 x 2) (2) (b) Give evidence from the QUESTION 6.1.1(a) photograph to support your answer. (1 x 1) (1) (c) State TWO physical factors that will influence the discharge (stream flow) of this river. (2 x 2) (4) 6.1.2 (a) What do you call a permanent river that flows through dry areas? (1 x 2) (2) (b) Explain why the river in QUESTION 6.1.2(a) flows throughout the year. (2 x 2) (4) (c) State TWO advantage of this river for farmers in the north-western part of South Africa. (2 x 2) (4) 16 7. DRAINAGE PATTERNS A. KEY CONCEPTS Concept Explanation Pattern Arrangement of stream in a drainage basin Resistant to erosion Hard rock that does not erode easily Underlying rock structure Type of rock on which the river system flow Alternate layer Layers of hard and soft rock next to one another B. NOTES AND EXPLANATIONS UNDERLYING ROCK PATTERN SKETCH /DIAGRAM EXAMPLE STRUCTURE Dendritic pattern Found in areas with rocks of equal Tributaries join the resistance to erosion main stream at acute angles. Resembles the branches of a tree. 17 Trellis pattern Occurs in areas of folded sedimentary Tributaries join the rocks. main stream at right angles. Occurs in areas where hard rocks and Main streams are soft rocks alternate. parallel to each other Radial Pattern Found in areas with dome like structures Streams radiate from a central point. Rectangular Found in areas with Pattern igneous rocks with joints and cracks. The mainstream displays right-angle bends. 18 Deranged Pattern Occur in regions subjected to glaciation Streams have irregular patterns. Tributaries do not link up with the main stream Centripetal Basin like structure Pattern Streams converge into a low-lying area. rivers discharge their waters from all directions in a lake or depression 19 Parallel Pattern Parallel drainage patterns form where Pattern of rivers there is a pronounced caused by steep slope to the surface. slopes with some relief. Because of A parallel pattern also the steep slopes, develops in regions of the streams are parallel, elongate swift and straight, landforms like with very few outcropping resistant tributaries, and all rock bands flow in the same direction. 20  C. DRAINAGE PATTERNS ACTIVITIES 7.1 FIGURE 7.1 illustrates a drainage basin. [Source: Adapted from Hydrology and landforms] 7.1.1 Define the term drainage basin. (1 x 1) (1) 7.1.2 Identify the drainage pattern assumed by the river system in this drainage basin. (1 x 1) (1) 7.1.3 Give ONE reason, visible in FIGURE 7.1, for your answer to QUESTION 7.1.2. (1 x 1) (1) 7.1.4 The drainage density of the river system seems to be denser (finer) at R than at S. Explain why this is the case. (1 x 1) (1) 7.1.5 Determine the stream order of the river system where it flows at X. (1 x 1) (1) 7.1.6 (a) At which point, R or S, would there be a greater risk of flooding? (1 x 1) (1) (b) Explain your answer to QUESTION 7.1.6(a). (1 x 1) (1) (c) Write a short paragraph (approximately 8 lines) outlining flood prevention methods that can be implemented to reduce the risk of flooding in this drainage basin. (4 x 2) (8) 21 7.2 Choose the term in COLUMN B that matches the statement in COLUMN B. You can choose one term for more than one response. COLUMN A COLUMN B 7.2.1 A pattern found in areas that experienced A Dendritic pattern glaciation. 7.2.2 The underlying rock is a dome like B Centripetal pattern structure. 7.2.3 Occurs in areas of folded sedimentary C Rectangular rocks. pattern 7.2.4 Main stream and tributaries all flow in the D Radial pattern same direction on a steep slope. 7.2.5 Pattern found on a basin like structure E Trellis pattern 7.2.6 Tributaries join the main stream at acute F Deranged pattern angles. 7.2.7 Underlying rock structure has cracks and G Grid pattern joints. 7.2.8 Streams converge into a low-lying area. H Parallel pattern I Linear pattern (8 x 1) (8) 22 7.3 Study the FIGURE 7.3 below and answer the questions that follow. 7.3.1 What is a drainage pattern? (1 x 2) (2) 7.3.2 Identify drainage patterns A and C. (2 x 1) (2) 7.3.3 Compare the underlying rock structures of drainage patterns B and C. (2 x 2) (4) 7.3.4 Account for the direction of the stream flow in patter A. (2 x 2) (4) 7.3.5 Explain why drainage pattern B is suitable for farming? (2 x 2) (4) 7.3.6 Draw a simple, labelled plan view sketch of a drainage pattern that will develop in a folded landscape. (2 x 2) (4) 23 MAP WORK APPLICATION 7.4 Refer to the Topographic Map extract and answer the questions that follow. 7.4.1 Name the type of river at A. (1 x 1) (1) 7.4.2 Explain the purpose of the human-made feature at B. (1 x 1) (1) 7.4.3 Name drainage patterns C and D. (2 x 1) (2) 7.4.4 Discuss the reasons for the development of the respective drainage patterns C and D. (2 x 2) (4) 7.4.5 Explain why the location of the Blyderivierpoort Dam is ideal. (2 x 2) (4) 24 8. DRAINAGE DENSITY The drainage density is the measure of the length of stream channel per unit area of drainage basin. It describes how many streams there are in a drainage basin. Drainage Density is affected by infiltration and surface runoff. A. KEY CONCEPTS Infiltration: Water soaks or filters into the soil Surface runoff: Water moves across the surface of the earth becoming a stream, tributary or river. 25  B. FACTORS INFLUENCING DRAINAGE DENSITY A decrease in precipitation such as in an arid environment results in lower drainage density soil with little high evaporation rate will lead to fewer moisture will result in high infiltration and number of streams less streams LOW DRAINAGE DENSITY high porosity and areas with high high permeability vegetation cover will lead to high will have high infiltration and less infiltration and less streams streams slope/gradient Gentle slopes will promote high infil;tration and less streams 26  Increase in precipitation results in high run-off Low evaporation Soil with high rate will lead to high moisture will result number of streams in low infiltration and high run-off HIGH DRAINAGE DENSITY Areas with little Low porosity and low vegetation cover permeability will lead will have little to high run-off infiltration and high run-off Slope/Gradient Steep slopes will promote high run-off and less infiltration 27  C. DRAINAGE DENSITY ACTIVITIES 8.1 Refer to FIGURE 8.1 which shows drainage basins. 8.1.1 Explain the concept drainage density. (1 x 2) (2) 8.1.2 Compare the drainage density at A and at B. (2 x 2) (4) 8.1.3 Describe two factors that may have resulted to the drainage density at B. (2 x 2) (4) 8.1.4 Write a paragraph of approximately EIGHT lines discussing how human activities could have impacted on the drainage density at A. (4 x 2) (8) 28 8.2 The diagram below represents drainage densities, study it and answer the questions that follow. [Adapted from: https://gis4geomorphology/com/wp-ontent/uploaded/201403threshold.jpg] 8.2.1 Define the term drainage density (1 x 2) (2) 8.2.2 Which ONE of the drainage basins, A or B, shows the drainage density during the dry season and rainy season respectively? (1 x 2) (2) 8.2.3 Explain why the drainage density of the drainage basins changes during the course of the year. (2 x 2) (4) 8.2.4 The change in drainage density changes the stream order of the drainage basin over the course of a year. In a paragraph of approximately EIGHT lines, explain why this is the case. (4 x 2) (8) 29 9. STREAM ORDERS A. KEY CONCEPTS AND NOTES 1st order streams 2nd order streams 3rd order streams below the junction of the The smallest stream in When two first order second order streams the the river is classified streams join 1 + 1 they stream become a third order as first order stream, become second order stream first order streams stream (2) below their have no tributaries joining place NOTE If a second order stream joins the third order stream the stream below the junction remains a third order stream B. LAWS OF STREAM ORDERS The steeper the slope the lower the stream order The bigger the drainage basin the higher the stream order The longer the stream the higher the stream order There are more lower order streams than higher order stream 30  C. ACTIVITY ON MAP WORK APPLICATION OF STREAM ORDERS 9.1 Refer to the Topographic Map extract and answer the questions that follow: 9.1.1 Is the drainage density in the mapped area high or low? (1 x 1) (1) 9.1.2 Discuss how the topography in the mapped area influenced the drainage density you mentioned in QUESTION 9.1.1. (2 x 2) (4) 9.1.3 Determine the stream order at A. (1 x 2) (2) 9.1.4 Predict the likely stream order at A, in the dry season. Give a reason for your answer. (1 + 2) (3) 31  10. RIVER DISCHARGE A. KEY CONCEPTS AND NOTES TURBULENT LAMINAR FLOW FLOW Turbulent flow is water motion characterised by Laminar flow is water motion chaotic changes in characterised by smooth pressure and velocity layers of water Water flows bubbly Water flows in parallel sheets Riverbed is uneven Riverbed is even More erosion Less erosion 32  B. FLUVIAL PROCESSES What are Fluvial The physical interaction of flowing water and Processes? the natural channels of rivers and streams TYPES OF FLUVIAL PROCESSES TRANSPORTATION DEPOSITION EROSION It is the It is the process processes in It is a process in in which eroded which materials which material are materials are dumped are removed by an agent carried away How do the Primarily vertical erosion. Large boulders deposited fluvial and eroded. Continues to cut vertically, but it also processes work begins to cut laterally as it gets closer to the lowest together? point. Deposition occurs in the slower moving insides of meanders 33 11. RIVER PROFILES AND THE STAGES OF A RIVER A. LONGITUDINAL PROFILE AND STAGES OF A RIVER (Longitudinal profile - Side view of a river from source to mouth) UP PE RC B. C OU RO RS E SS MIDDL E COU RSE MIDDL LOWER COUR E COU SE RSE LOWER COUR SE Vertical erosion decreases and lateral erosion dominates Deposition dominates with very little Vertical erosion deepens the valley The channel becomes wider erosion Straight stream channel with short The river starts to meander due to lateral The channel is at its widest non-perennial streams erosion Extensive meandering of the river Turbulent flow due to uneven Tributaries join the mainstream, increasing due to the flat surface and lateral riverbed and valley slopes the volume and erosive power movement of the river Waterfall and rapids are being Both laminar and turbulent flow occurs Laminar flow dominates due to the eroded through headward erosion depending on the roughness of the riverbed smooth riverbed and sides Large stream load with big boulders and the sides Suspension and solution load Traction load Saltation load occurs dominates Load becomes smaller due to attrition and Very large load but smaller particles abrasion 34  B. CROSS /TRANSVERSE PROFILE: FRONT VIEW OF A RIVER Upper course Middle course Lower course V-shaped valleys U-shaped valleys Wide open Waterfalls River starts to meander valley Rapids Floodplain Deltas 35 12. RIVER GRADING A. KEY CONCEPTS AND NOTES River grading: This is the balance/equilibrium between rate of erosion and rate of deposition. GRADING Graded Rivers Ungraded Rivers When there is a balance between erosion When either erosion or deposition and deposition dominates LONGITUDINAL PROFILES OF GRADING Graded Profile Ungraded Profile The longitudinal profile is The longitudinal profile indicates SMOOTH CONCAVE knick points like waterfalls and Steep in the upper course and gentle rapids. in the lower course The profile is therefore not smooth concave. 36  B. BASE LEVELS OF EROSION Permanent / Ultimate base level of Temporary / Local base level erosion When features/ structures delay further erosion The lowest level to which a river This local base level causes a knick point in the can erode. profile, making it ungraded. It is usually sea level Types of local base levels Human-made Natural e.g., lakes, e.g., dams waterfalls, rapids Processes involved in a river becoming graded from ungraded. Downward/Vertical erosion dominates in the upper course causing a steep valley slope. Headward erosion removes temporary base levels of erosion in the upper course. Downward/Vertical erosion removes temporary base levels (waterfall) in the upper course. This material is then transported downstream. Discharge of the river increases in middle course causing lateral erosion. Gradient in the middle course becomes less steep. Deposition dominates in the lower course because the gradient is gentle. Deposited materials fill up lakes and dams. The river profile will now develop a concave shape from upper to lower course. Equilibrium between erosion and deposition will maintain (result in) a graded profile. 37  C. RIVER GRADING ACTIVITIES 12.1 FIGURE 12.1 illustrates the stream profiles of a typical South African river from its source to its river mouth. [Adapted: Hydrology and Landforms] 12.1.1 Define the term base level of erosion. (1 x 2) (2) 12.1.2 Identify ONE temporary base level of erosion in FIGURE 12.1 (1 x 1) (1) 12.1.3 Draw a labelled longitudinal profile of the river illustrated in FIGURE 12.1, clearly showing how the temporary base levels of erosion could have influenced the shape of the profile.(3 x 1) (3) 12.1.4 How would you describe the longitudinal profile that you have drawn in QUESTION 12.1.3? (1 x 2) (2) 12.1.5 Give a reason for your description in QUESTION 12.1.4. (1 x 2) (2) 12.1.5 Suggest THREE reasons why the cross-section profiles of the river change, from its source (1) to its river mouth (2). (3 x 2) (6) 38 MAP WORK APPLICATION 12.2 The map is an extract of 2930CA MERRIVALE. 12.2.1 In which stage is the Gqishi river at A and B on the topographic map. (2 x 1) (2) 12.2.2 Provide map evidence as reasons for your answers to QUESTION 12.2.1. (2 x 1) (2) 12.2.3 Explain the characteristics of the erosion in stages A and B. (2 x 2) (4) 12.2.4 Determine the stream order at C. (1 x 2) (2) 39 13. FLUVIAL LANDFORMS IN THE DIFFERENT STAGES OF THE RIVER A. KEY CONCEPTS AND NOTES Fluvial landforms are those landforms generated by running water, mainly rivers. Some features are a result of river erosion and some a result of river deposition. 1. MEANDERS A meander is defined as a distinct curve or loop in the course of a river channel. Formation In the middle course the river has more energy and a high volume of water as a result of tributaries joining Lateral (sideways) erosion starts to widen the river channel. As the river erodes laterally (to the right side then the left side) it forms large bends, and then horseshoe-like loops called meanders. The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream 1. MEANDERS Two slopes with different characteristics develop at the meander loop. A meander is defined as a distinct curve or loop in the course of Undercut slope a river channel. Slip-off slope This slope develops at the outer This slope develops at the inner bank. bank. Formation In the middle course the river has more Characteristics: energy and a high volume of water as a result of tributaries joining This slope is convex. Characteristics: The slope Lateral is concave. (sideways) The erosion starts to widen river channel. the river flows slow at this side. The river flows fast at this side. As the river erodes laterally (to the right side then theoccurs. Deposition left side) it Erosion, forms largeespecially undercutting bends, and The then horseshoe-like slope loops is shallow. called meanders. occur The formation of meanders is due to both deposition and The areaand erosion is deep. meanders gradually migrate downstream 40 2. OXBOW LAKE The cut-off meander loop filled with water is called an oxbow lake. Continuous undercutting at the outer bank and deposition at inner bank Causes the horseshoe to become tighter over time, until the ends become very close together. During heavy rainfall and flooding the river breaks through the ends Significance of OXBOW LAKES The loop is cut-off from the main channel. Oxbow lakes can be rich wildlife habitats, Can be utilised for agricultural purposes especially crop farming. 2. OXBOW LAKE Tourist attractions The cut-off meander loop filled with water is called How is the water in the oxbow lake maintained? an oxbow lake. During rainfall periods Continuous undercutting at the outer bank and Flooding of the mainstream deposition at inner bank Underground water Causes the horseshoe to become tighter over time, until the ends become very close together. Development of MEANDER SCARS During heavy rainfall and flooding the river breaks (Dry oxbow lake) through the ends Decrease in average rainfall over the years. The loop is cut-off from the main channel. Silt deposits from flooding 41 3. BRAIDED STREAM: A stream consisting of multiple small, shallow channels (distributaries) They divide and recombine numerous times forming a Significance of BRAIDED STREAMS pattern resembling the strands of a braid. Source of water for crop farming Silt deposits form fertile soil. Formation Area preserves bird life. Braided streams form where the sediment load is The area hampers the deposited as shifting islands or bars between the construction of infrastructure. channels It is therefore expensive to build roads When the river’s carrying capacity is exceeded the river and railway lines. deposits its load into the channel. 3. BRAIDED STREAM: A stream consisting of multiple small, shallow channels (distributaries) They divide and recombine numerous times forming a pattern resembling the strands of a braid. Formation Braided streams form where the sediment load is deposited as shifting islands or bars between the channels When the river’s carrying capacity is exceeded the river deposits its load into the channel. 42 4. FLOOD PLAIN Significance of FLOOD PLAINS Floodplains provide fertile land for agriculture. A wide, flat area of land surrounding a river that Easy to construct infrastructure. continuously flood. Flat area is heavily populated. Settlements develop. Formation Tourist attraction Source of water for economic and domestic Floodplains form due to mainly deposition. purposes Because of the gentle gradient, there is more They are beneficial for wildlife by creating a deposition occurring. variety of habitats for fish and other animals. The heavier load (rocks and pebbles) is deposited It preserves water quality by continuous closer to the banks of the river. refreshing due to flooding. It provided numerous recreational Lighter and smaller load is dropped further away opportunities. from the river banks. 4. FLOOD PLAIN A wide, flat area of land surrounding a river that continuously flood. Formation Floodplains form due to mainly deposition. Because of the gentle gradient, there is more deposition occurring. The heavier load (rocks and pebbles) is deposited closer to the banks of the river. Lighter and smaller load is dropped further away from the river banks. 43 5. NATURAL LEVEE Levees are natural embankments (raised river banks) which are formed when a river flood. Significance of NATURAL LEVEES Formation They prevent rivers from flooding. Levees are usually parallel to the way the river Levees are formed by the repeated flooding of the river. flows, so levees can help direct the flow of the When the river floods, the biggest, most coarse material will river. be deposited. Levees can also provide a measure of protection This will be close to the river banks. from invaders. Continuous flooding causes repeated deposition on the Fertile soil near levees is suitable for farming. river banks. Levees may be used to increase available The banks form levees made of sediment, silt, and other land for habitation. materials. 5. NATURAL LEVEE Levees are natural embankments (raised river banks) which are formed when a river flood. Formation Levees are formed by the repeated flooding of the river. When the river floods, the biggest, most coarse material will be deposited. This will be close to the river banks. Continuous flooding causes repeated deposition on the river banks. The banks form levees made of sediment, silt, and other materials. 44 6. DELTAS Significance of DELTAS Deltas are usually highly fertile areas and support It is landform at the mouth of a river, where different extensive crop cultivation. channels (distributaries) of the same river flow into an Sand and gravel are also quarried from deltas and ocean or sea. are utilized for a variety of purposes e.g., road and building construction. Formation They are important industrial hubs. The river slows down at the mouth due silt Large settlements often grow up in the delta regions. deposits and gentle gradient. Deltas are a source of water. The channel splits into several smaller channels Deltas sustain all ecosystems. (distributaries) and it loses velocity. Deltas ensures biodiversity. As the river loses velocity it deposits its load on Tourism(leisure activities) opportunities are created the river bed. by deltas and contributes to the economy. Both the bed load and suspended load are Can be part of water transport system. deposited producing fertile alluvial land. Deltas are a source of protein (fish) 6. DELTAS It is landform at the mouth of a river, where different channels (distributaries) of the same river flow into an ocean or sea. Formation The river slows down at the mouth due silt deposits and gentle gradient. The channel splits into several smaller channels (distributaries) and it loses velocity. As the river loses velocity it deposits its load on the river bed. 45 Both the bed load and suspended load are deposited producing fertile alluvial land. 7. WATERFALLS A waterfall is an area where water flows over a vertical drop or a series of steep drops in the course of a stream or river. Significance of WATERFALLS The strong currents near falls are often used to generate Formation hydro- electricity. Waterfalls often form in the upper stages of a river where Waterfalls are sometimes a disadvantage since they form it flows over different layers of rock. a barrier to infrastructure development. The soft rock erodes more quickly, undercutting the hard Waterfalls attract tourists. rock. Fishing can be carried out on waterfalls. The hard rock is left overhanging and because it is not Waterfalls is aesthetically pleasing. supported, it eventually collapses. Waterfalls also provide opportunities for a wide range of, sometimes incompatible, outdoor leisure activities. The fallen rocks crash into the plunge pool. They swirl around, causing more erosion. Over time, this process is repeated, and the waterfall moves upstream. A steep-sided gorge is formed as the waterfall retreats. 7. WATERFALLS A waterfall is an area where water flows over a vertical drop or a series of steep drops in the course of a stream or river. Formation Waterfalls often form in the upper stages of a river where it flows over different layers of rock. The soft rock erodes more quickly, undercutting the hard rock. The hard rock is left overhanging and because it is not supported, it eventually collapses. The fallen rocks crash into the plunge pool. They swirl around, causing more erosion. 46 Over time, this process is repeated, and the waterfall moves upstream. A steep-sided gorge is formed as the waterfall retreats. 8. RAPIDS Rapids are areas of shallow, fast-flowing water in a stream. Rapids are stretches of fast-flowing water tumbling over a Significance of RAPIDS rocky-shallow riverbed. Attract tourists who want to raft down the stream. Formation Water splashing over rocks is called white- water and it dissolve oxygen. Water goes from one hard rock to softer rock The oxygen is useful to the ecosystem around Rock layers below the water is exposed the stream e.g., fish, insect and bacteria in the Flowing water splashes over and around the rocks, water. forming what is called “white water”. 8. RAPIDS Rapids are areas of shallow, fast-flowing water in a stream. Rapids are stretches of fast-flowing water tumbling over a rocky-shallow riverbed. Formation Water goes from one hard rock to softer rock Rock layers below the water is exposed Flowing water splashes over and around the rocks, forming what is called “white water”. 47  B. FLUVIAL LANDFORMS AND FEATURES ACTIVITIES 13.1 Study FIGURES 13.1 A and 13.1 B showing fluvial landforms. FIGURE 13.1A FIGURE 13.1B 13.1.1 Refer to FIGURE 13.1 A (a) Define the term river discharge. (1 x 2) (2) (b) Identify feature X. (1 x 1) (1) (c) Along which course of the river does this feature commonly occur? (1 x 1) (1) (d) Give a reason for your answer in QUESTION 13.1.1 (c). (1 x 1) (1) (e) Account for the formation of feature X. (2 x 1) (2) (f) Explain how feature X contributes to the economy of a country. (1 x 1) (1) 48 13.1.2 (a) Identify feature labelled Y. (1 x 1) (1) (b) Name ONE popular sport that takes place at Y. (1 x 1) (1) 13.1.3 Refer to FIGURE 13.1 B showing a meandering river channel. “Distinctive landforms (features) develop along the course of a river as a result of erosion or deposition.” (a) Define the term meander. (1 x 2) (2) (b) Explain how a meander develops. (2 x 1) (2) (c) Describe ONE characteristic of the “undercut slope” in a meander. (1 x 1) (1) (d) Name the feature that will result from the narrowing of the meander neck. (1 x 1) (1) (e) Suggest ONE reason why the feature identified In QUESTION 13.1.3(d) is classified as a “temporary feature”. (1 x 1) (1) 49 13.2 Study the FIGURE 13.2 below and answer the questions that follow. [Adapted from easymapwork.blogspot.com] 13.2.1 Identify fluvial landform C on the sketch. (1 x 1) (1) 13.2.2 In which course of the river is this landform found? (1 x 1) (1) 13.2.3 Identify slopes A and B. (2 x 1) (2) 13.2.4 Account for the differences in the gradient of slopes A and B. (2 x 2) (4) 13.2.5 Explain what will happen to feature C over time. (2 x 2) (4) 13.2.6 Mention one significance of the landform C. (1 x 2) (2) 50 13.3 Refer to the cartoon which illustrates activities at a river bend. [Source: Ucdenver.org] 13.3.1 What is the term used to describe a river that winds and bends? (1 x 1) (1) 13.3.2 Name the TWO dimensions of a river that are visible in the cross profile. (2 x 1) (2) 13.3.3 Name the slope of the river at B. (1 x 1) (1) 13.3.4 Why does the fish think both boys are idiots? (2 x 2) (4) 13.3.5 In a paragraph of approximately EIGHT lines, give a detailed explanation to account for the difference in the formation of slope A and slope B. (4 x 2) (8) 51 MAP WORK APPLICATION 13.4 Refer to the topographic map and an extract of an orthophoto map of the same area. 52 13.4.1 Name the dominant fluvial landform evident on the topographic map. (1) (1 x 1) 13.4.2 Refer to fluvial feature A (a) Name fluvial feature A. (1 x 1) (1) (b) How did the fluvial feature mention in QUESTION 13.4.2 (a) influenced the construction of roads in the area? (1 x 2) (2) 13.4.3 Refer to the orthophoto map, which is a part of the topographic map. (a) Draw a labelled cross section from 1 to 2 on the orthophoto map. (4 x 1) (4) (b) Explain how the dominant geomorphological process at 1 influenced agricultural activities. (1 x 2) (2) 53 13.5 The topographic map is part of the 2829AC HARRISMITH. 13.5.1 The Nuwejaarspruit (river) is in its lower course. Provide TWO evidences from the topographic map to support this statement. (2 x 1) (2) 13.5.2 Explain the impact of the Nuwejaarspruit (river) on human activities in the area. (2 x 2) (4) 13.5.3 Identify fluvial features A and B. (2 x 1) (2) 13.5.4 Discuss why the existence of landform feature A help to reduce flooding. (2 x 2) (4) 54 14. RIVER REJUVENATION A. KEY CONCEPTS AND NOTES Explanation Characteristics Definition It is made young River flows faster and When a river regains (gaining erosive power) vertical erosion its erosive power again and starts eroding increases DROP IN SEA LEVEL INCREASE IN RAINFALL CAUSES OF STREAM PIRACY/RIVER CAPTURE REJUVENATION ISOSTATIC UPLIFT DECREASE IN STREAM LOAD B. RESULTANT LANDFORMS River terraces: Knick point: Incised meanders: Bench or step that Part of a river channel where The curve of a winding river extends along the side there is sharp change in channel with steep slopes on both of the valley and slope such as a waterfall or lake. sides rising to the former represents former level A point where the new profile floodplain of the valley floor meets the old profile 55 IMPORTANCE OF REJUVENATED LANDSCAPES Landforms are good for tourist attractions. People can visit areas with terraces for recreation. Old flood plain suitable for crop farming People can visit areas with terraces for recreation. Water at the knick point waterfalls can be used for power generation. C. RIVER REJUVENATION ACTIVITIES 14.1 The FIGURES below illustrated the process of rejuvenation. [Adapted from https://www.google.com/search?q=rejuvenation+of+rivers] 14.1.1 What type of erosion is associated with river rejuvenation? (1 x 1) (1) 14.1.2 What evidence indicates that river rejuvenation has taken place? (1 x 2) (2) 14.1.3 Identify the force of upliftment associated with rejuvenation. (1 x 2) (2) 14.1.4 Why is rejuvenated land not suitable for human activity? (2 x 2) (4) 14.1.5 In a paragraph of approximately EIGHT lines, explain how rejuvenation could change the fluvial features downstream of the point of rejuvenation. (4 x 2) (8) 56 14.2 FIGURE 14.2. represents river rejuvenation. [Source: https://alevelrivers.weebly.com/rejuvenation.html] 14.2.1 Define the term river rejuvenation. (1 x 2) (2) 14.2.2 Identify the condition that resulted in river rejuvenation. (1 x 1) (1) 14.2.3 Name ONE fluvial feature that can form at the knick point along the (2) river profile. (1 x 2) 14.2.4 Explain the impact of river rejuvenation on the grading of a river. (2 x 2) (4) 14.2.5 Write a paragraph of approximately EIGHT lines elaborating on the changes that will occur in the fluvial features found in the illustrated course of the river as a result of river rejuvenation. (4 x 2) (8) 57 15. RIVER CAPTURE/STREAM PIRACY A. KEY CONCEPTS AND NOTES Concepts Definition River capture/stream When the more energetic (active) river, captures some of the piracy water of a less energetic river. Abstraction The process whereby the watershed becomes lower and its position shifts. Headward erosion The stream erodes away at the rock and soil at its headwaters (source) in the opposite direction that it flows. This lengthens the Erosion takes place stream channel and enlarge the drainage basin towards the source of a river. Headwaters of a river are moving upstream. Upper stream is moved backward. Undercutting of upper reaches of river Less resistant rocks promote the erosion process. 58  B. CAUSES AND CHARACTERISTICS 1. Causes of stream piracy. Steeper gradient on the side of the energetic stream of the watershed. The low-lying stream has more energy. Higher precipitation, giving greater runoff and more erosion to the energetic stream. Softer rocks on the side of the energetic stream cause faster erosion. Presence of faults or joints in rocks to assist the erosion process. How does stream piracy occur. The more energetic stream erodes backward at its source. The energetic stream captures the waters of the less energetic stream. FEATURE EXPLANATION The energetic stream that intercepts (takes) the water of the less Captor Stream energetic stream The river from which water was intercepted (taken) by the captor Captured Stream stream) The stream that has lost his water. Also called beheaded stream. Misfit Stream The river is too small for then valley it flows in The place at which stream piracy (river capture) takes place. Elbow of capture Usually, a knickpoint waterfall develops. The dry river valley between the misfit stream and the elbow of Wind gap capture. 59 Characteristics of Captor stream after piracy Volume of water increases in the stream. Downward erosion increases. Carrying capacity of the river increases. River rejuvenates. Characteristics of misfit stream after stream piracy Volume of water decreases Stream too small for its channel/valley Deposition of stream load occurs. Water erosion is reduced, but wind erosion will increase. Carrying capacity is reduced. 2. IMPLICATIONS OF RIVER CAPTURE 1. Human activities At the Captor Stream At the Misfit Stream More agricultural production People will relocate due to job losses in Less irrigation agriculture. Increase in production might lead Decrease in agricultural production. to manufacturing. Financial implication due to irrigation Increase in water might cause Less of recreational facilities due to less flooding and people must relocate. income More water might have damaged the Factories close due to lack of water recreational facilities on the banks of Decrease in fishing for source of food the river. 2. Settlements Captor Stream Misfit Stream Due to increase of water along Due to the decrease in agricultural the banks people must relocate. production people relocate. Rural- urban migration The settlement might become a ghost town 3. Recreation Captor Stream Misfit Stream Recreational facilities along the Decrease in water sports. banks of the river might be damaged. Because of less people, there is financial Increase in water sports instability in the area 4. Agriculture Captor Stream Misfit Stream Increase in crop production. More water expenses. More exports Decrease in crop production Less irrigation 60  2. IMPLICATIONS OF RIVER CAPTURE 5. Ecosystem Captor Stream Misfit Stream Habitat will be disturbed. Marine/water ecosystem disturbed. Increase in water will cause an Less fish increase in fish. Land degradation due to soil erosion Diversity of ecosystems will develop Decrease in biodiversity because of the increase in vegetation. IMPLICATIONS OF RIVER CAPTURE Elbow of capture Wind gap Tourist attraction due to the waterfall Biodiversity is destroyed. Job creation in the tourism sector Decrease in crop production and farming There can be hydroelectricity activities. being generated. Soil erosion will increase. Area of research 61  C. STREAM PIRACY ACTIVITIES 15.1 Refer to sketches A and B of FIGURE 15.1 15.1.1 Define the term river capture. (1 x 2) (2) 15.1.2 Describe the erosion associated with the process of river capture in sketch A. (1 x 1) (1) 15.1.3 Identify features L and M that result from river capture. (2 x 1) (2) 15.1.4 Match the terms captor stream and misfit stream to streams J and K in diagram B. (2 x 1) (2) 15.1.5 (a) What is a watershed? (1 x 2) (2) (b) How can the process of river capture cause the watershed to change its position? (1 x 2) (2) 15.1.6 What effect will river capture have on the volume of water in stream K? (1 x 2) (2) 15.1.7 What can the local farming community around stream J do to continue with their daily activities after river capture have taken place? (2 x 2) (4) 62 15.2 Refer to the sketches that indicate the river capture process. 15.2.1 Identify streams S and Y. (2 x 1) (2) 15.2.2 Name the features of river capture at A and B respectively. (1 x 1) (1) 15.2.3 Give TWO reasons for the river S eroding at a faster rate. (2 x 1) (2) 15.2.4 In a paragraph of approximately EIGHT lines, explain the impact of river capture on the volume of water and the erosive ability of rivers B and S respectively. (4 x 2) (8) 63 16. SUPERIMPOSED AND ANTECEDENT DRAINAGE PATTERNS A. KEY CONCEPTS AND NOTES Concepts Definition Description Superimposed A drainage Rivers are younger pattern/stream than the structures that has been across which they established on cut. an earlier surface May cut narrow gab/gorges if forced across bands of hard rock Antecedent Occurs where a Rivers is older than river developed the landform across its course before which they cut. the high- lying Warping, folding or area was faulting occurred. formed. May cut narrow gab/gorges if forced across bands of hard rock B. Why the streams maintained their course Softer rock over which they flow. Volume of water increase through rejuvenation and increased rainfall. There are crack and joints where the river flows 64  C. SUPERIMPOSED AND ANTECENDENT DRAINAGE ACTIVTIES 16.1 Study FIGURE 16.1 which shows superimposed drainage (A) and antecedent drainage (B). 16.1.1 Distinguish between superimposed drainage and antecedent drainage. (2 x 2) (4) 16.1.2 Give ONE reason why superimposed drainage does not change its course. (1 x 2) (2) 16.1.3 Name ONE unique feature associated with the flow patterns of superimposed and antecedent drainage. (1 x 2) (2) 16.1.4 Identify the tectonic force associated with the uplift of the surface evident in diagram B. (1 x 2) (2) 16.1.5 Give the relationship between the rate of down cutting and tectonic uplift in antecedent drainage. (2 x 2) (4) 16.1.6 Explain why the illustrated landscapes are not suitable for human habitation. (2 x 2) (4) 65 17. CATCHMENT AND RIVER MANAGEMENT A. KEY CONCEPTS AND NOTES Concepts Definition River Management is defined as the management of water resources River management of a basin in relation to their socio-economic setting. The area from which rainfall flows into a river, Catchment area lake, or reservoir. Overgrazing Excessive grazing which causes damage to vegetation. Afforestation Planting more trees to reduce stream discharge and surface runoff Deforestation, clearing or thinning of forests by humans to make Deforestation the land available for other uses Environmental It is the poor treatment/use of the natural injustice resources/environment by humans B. CAUSES, IMPORTANCE AND IMPACT OF RIVER MANAGEMENT CAUSES OF POOR RIVER MANAGEMENT Inadequate sewage collection and treatment are sources of water pollution. Cutting down trees and concreting over large areas generates an acceleration of flows which does not give enough time for water to infiltrate and be purified by the ground. Agriculture has an impact on water pollution due to the use of chemicals such as fertilizers, pesticides or insecticides running off in the water, as well as livestock excrement, manure and methane (greenhouse effect). Industries produce a lot of waste containing toxic chemicals and pollutants. A huge amount of the industrial waste is drained in the fresh water which then flows into canals, rivers and eventually in the sea. Garbage such as plastic, paper, aluminum, food, glass, or rubber are deposited into the sea. IMPORTANCE OF MANAGING DRAINAGE BASINS Store water and protecting for future use. Reduce discharge and recycle harmful agricultural run-off. Agricultural purposes e.g., crop farming Industrial purposes e.g., to cool the machines in factories and is also a vital part of production. Control the flow of water to reduce the chances of flooding. Domestic purposes Recreation e.g., water sports Generation of Hydroelectricity Preserve natural vegetation. Preserve biodiversity. 66  River Pollution - Industrial waste - Sewage and waste water - Marine dumping - Accidental oil leakage - Burning of fossil fuels Causing acid rain - Chemical fertilizers and Industrial Waste pesticides Untreated Sewage - Untreated wastewater - Leakage from sewer lines - If untreated sewage gets pollute ground- and surface into rivers, microorganisms water decompose it. - Drinking water sources and - They use oxygen from irrigation water may be negatively affected the water - Aquatic biodiversity and - There is less oxygen in habitats may be destroyed water - Dumped chemicals - Aquatic organisms such as increases eutrophication fish is unable to survive. IMPACT OF PEOPLE ON DRAINAGE BASINS Deforestation Human Settlements Increases run-off causing - Increases waste dumping in silting in the rivers the river Impact of silting - Water quality decreases - Hydroelectric projects and leads to increased affected waterborne diseases - Irrigation infrastructure lose - Marine ecosystems and productivity biodiversity destroyed - Riverbed are raised - Eutrophication destroys water habitats Overgrazing increasing flood risk - Biodiversity is disturbed - Overgrazing increases soil erosion - This increases run-off that causes silting of the river - Salinity increases and nutrients are loss 67  Vegetation must be maintained in areas close to Legislation to rivers. control the Deforestation pollution of must be underground controlled. water. Avoid Legislation to construction control what is and discharged in settlements on rivers. the floodplains. ACTIONS TO ENSURE SUSTAINABLE USE OF DRAINAGE BASINS Greater care Research must be taken before new when altering dams is built river channels. Educate farmers on Wetlands must sustainable be conserved. farming methods. International cooperation to Educate public manage rivers on water that flow in conservation. more than one country. 68  C. CATCHMENT AND RIVER MANAGEMENT ACTIVITIES 17.1 The FUGURE below show catchment and river management. 17.1.1 What is the main source of wastewater? (1 x 1) (1) 17.1.2 Discuss how the removal of the natural vegetation for human activities increased the eroded soil and sediments in the river. (1 x 2) (2) 17.1.3 Explain how run-off from both settlements and cultivated land decreases the quality of water of a river. (2 x 2) (4) 17.1.4 In a paragraph of approximately EIGHT lines, discuss why sustainable river management is important for all sectors of the economy. (4 x 2) (8) 69 17.2 Refer to FIGURE 17.2 showing catchment and river management. 17.2.1 What is river management? (1 x 2) (2) 17.2.2 Name ONE way in which the factory pollutes the river. (1 x 2) (2) 17.2.3 Explain the importance of the wastewater treatment plant in river management. (2 x 2) (4) 17.2.4 State TWO ways in which fertilizers from the crop land can impact on the ecology of the river. (2 x 2) (4) 17.2.5 Outline the negative impact of water pollution on the economy of a country. (2 x 2) (4) 70 MAP IMPLICATIONS 17.3 2930CA MERRIVALE / 2930CA 5 MERRIVALE 17.3.1 Name features 1 and 2 on the orthophoto map. (2 x 1) (2) 17.3.2 Identify the slope represented by line 3-2. (1 x 1) (1) 17.3.3 Draw a rough cross profile from 3 to 2 to support your answer to QUESTION 13.3.2. (3 x 1) (3) 17.3.4 Discuss how human activities, evident on the topographic map, might influence the quality of water of the Midmar Dam. (2 x 2) (4) 71 18. POSSIBLE ANSWERS 5. DRAINAGE BASINS CONCEPTS 5.1 5.1.1 Surface runoff 5.1.2 Watershed 5.1.3 Ground water 5.1.4 Permanent 5.1.5 Water table 5.1.6 Confluence 5.1.7 Infiltration 5.1.8 Base flow (8 x 1) (8) 5.2 5.2.1 Total area drained by a river and its tributaries (1 x 2) (2) 5.2.2 Watershed: separates two drainage basins Interfluve: separates two streams (2 x 1) (2) 5.2.3 Precipitation (1 x 2) (2) 5.2.4 Built up area will promote high runoff. (1 x 2) (2) 5.2.5 There are artificial surfaces. No vegetation cover to increase infiltration. (2 x 2) (4) 5.2.6 Inadequate sewage collection and treatment are sources of water pollution. Cutting down trees does not give enough time for water to infiltrate and be purified by the ground. Use of chemicals such as fertilizers, pesticides or insecticides running off in the water, as well as livestock excrement, manure and methane (greenhouse effect). A huge amount of the industrial waste is drained in the fresh water which then flows into canals, rivers and eventually in the sea. Garbage such as plastic, paper, aluminium, food, glass, or rubber are deposited into the sea. (4 x 2) (8) 5.3 5.3.1 drainage basin (1 x 1) (1) 5.3.2 B: watershed (2 x 1) (2) C: interfluve 5.3.3 Refer to D (1 x1) (1) c) Easterly d) Tributaries join the main stream in an easterly direction. Contour lines point towards the opposite direction of flow. (2 x 2) (4) 5.3.4 F- confluence has more water joining the streams (1 + 2) (3) 72 6. TYPES OF RIVERS 6.1 6.1.1 a) A river that only flows after heavy rainfall, short duration (2) (1 x 2) (2) b) Many rocks and boulders visible in the river course (1) Dry river bed (1) (1 x 1) (1) c) Regularity of rainfall/droughts (2) Amount of rainfall (2) Soil type over which the streams flow (2) Underlying rock structure (2) Rate of evaporation (2) Vegetation density in catchment area (2) The speed/velocity at which the water flows (2) The volume of flowing water/floods (2) The manner in which the water flows (2) Infiltration rate (2) Soil water content (2) Gradient (2) [ANY TWO] (2 x 2) (4) 6.1.2 a) Exotic river (2) (1 x 2) (2) b) Gains water in much wetter areas – Drakensberg Mountains (2) Stream flow volume exceeds infiltration rate (2) Fed by tributaries in high rainfall areas (2) Reliable ground water close to the source (2) Construction of dams to regulate the flow of water (2) [ANY TWO] (2 x 2) (4) e) Regular water supply (2) Irrigation (2) Stock farming (2) [ANY ONE – ACCEPT OTHER] (2 x 2) (4) 7. DRAINAGE PATTERNS 7.1 7.1.1 Total area drained by a river and its tributaries. (1 x 1) (1) 7.1.2 Trellis Pattern (1 x 1) (1) 7.1.3 Tributaries join the main stream at right angles (1 x 1) (1) 7.1.4 Steep slopes at R more erosion. (1 x 1) (1) 7.1.5 3rd order (1 x 1) (1) 7.1.6 a) At S (1 x 1) (1) b) More water in the river Gentle gradient (1 x 1) (1) c) More load and the river is entering the sea Plant more vegetation along the river banks Building artificial levees Divert the channel flow of rivers (4 x 2) (8) 73 7.2 7.2.1 F 7.2.2 D 7.2.3 E 7.2.4 H 7.2.5 B 7.2.6 A 7.2.7 C 7.2.8 B (8 x 1) (8) 7.3 7.3.1 The way in which streams are arranged within a drainage basin/ The surface pattern formed by a river and its tributaries. (1 x 2) (2) 7.3.2 A. Radial pattern C. Rectangular pattern (2 x 1) (2) 7.3.3 Pattern B: found on a rock with a uniformed resistance to erosion. Pattern C: found on an igneous rock with cracks and joints. (2 x 2) (4) 7.3.4 High lying area at the center. Streams are flowing outwards from a central elevated point. Dome like structure at the center will cause water to flow in all directions. (Any ONE) (1 x 2) (2) 7.3.5 In the dendritic pattern water is widely distributed in the drainage basin and water is accessible Longer tributaries therefore water is more accessible Occurs over flat/gentle land (middle/lower course) thus more suitable for farming Larger floodplains with access to fertile soils (2 x 2) (4) 7.3.6 (2 x 2) (4) 7.4 7.4.1 Permanent (1 x 1) (1) 7.4.2 Because of the bridge to cross the river. (1 x 2) (2) 7.4.3 C – Parallel D – Trellis (1 x 2) (2) 7.4.4 C – steep slope all streams flowing down in one direction. D – tributaries join main stream at right angles 90°. (2 x 2) (2) 7.4.5 The Dam is located in the basin. Lots of tributaries flowing towards the center. (2 x 2) (4) 74 8. ACTIVITY DRAINAGE DENSITY 8.1 8.1.1 Total number of streams found in an area. (1 x 2) (2) 8.1.2 A. density is high B. density is low (2 x 2) (4) 8.1.3 High vegetation cover results in high infiltration rate and less streams on the surface. Little rainfall will lead to few streams on the surface High porosity and permeability will result in high infiltration and less streams. Gentle slopes will lead to high rate of infiltration and less runoff. Soil with little moisture will lead to high amount of infiltration and low density. (2 x 2) (4) 8.1.4 Clearing of natural vegetation/deforestation will increase run-off (2) Overgrazing by animals removes natural vegetation which increases run-off (2) Incorrect ploughing methods can result in more water flowing down the furrows (2) Over-cultivation of farmland destroys vegetation and top soil (2) The loss of topsoil due to human activities can result in the formation of gullies (dongas) (2) Building of settlements increases artificial surfaces therefore more run-off (2) Building of canals to divert run-off create more river channels (2) Building of roads reduces natural vegetation which increases run- off (2) Open cast mining causes removal of natural vegetation increasing run-off (2) Trampling of soil by livestock decreases infiltration (2) [ANY FOUR] (4 x 2) (8) 75  8.2 8.2.1 The ratio between the total length of all the streams in a river system and the area of the drainage basin that it drains (1 x 2) (2) 8.2.2 A: Dry season B: Rainy season (1 x 2) (2) 8.2.3 In the wet season drainage density will be high due to high rainfall (often soil is saturated) and a high rate of run-off occurs (2) In the dry season the drainage density will be low due to low rainfall and high rate of infiltration occurring (2). (2 x 2) (4) 8.2.4 IMPACT OF DRAINAGE DENSITY ON DRAINAGE BASIN ORDER In the wet season there will be higher rainfall, which leads to higher volumes of water (2) leading to more 1st and 2nd order streams/rivers (2) The area will have high rates of run-off (2), as soils will be saturated (2) This increases the drainage basin order (2) In the dry season there will be less run-off due to less rainfall (2) Less 1st and 2nd order streams will be found (2) The area will have higher levels of infiltration creating lower drainage densities (2) This decreases drainage basin order (2) [ACCEPT OTHER REASONABLE ANSWERS] (4 x 2) (8) 9. STREAM ORDERS 9.1 9.1.1 High (1 x 1) (1) 9.1.2 Steep