The questions should be answered as required. There should be 1 point made per mark so questions 1 will have 10 points, 2 will have 10 points, and 3 will have 15. Please follow the criteria.
The area chosen isHoldfast Shores SA for the coastline.
UNIVERSITY OF SOUTH AUSTRALIA Engineering & Environmental Geology Page 1 Metro Beaches Background Info UNIVERSITY of SOUTH AUSTRALIA School of Natural and Built Environments, Mawson Lakes ENGINEERING & ENVIRONMENTAL GEOLOGY (ENR 120) Coastal processes This exercise deals with the Adelaide metropolitan coastline, mainly in the area between Kingston Park to the south and Outer Harbor to the north. This region is of considerable value to the inhabitants of Adelaide and its surrounds, both as a recreational area and as a place to live. As we will see, engineering and environmental science play a vital role in protecting this natural environment and preserving its sustainability. On completion of this practical, you should be able to: Interpret aerial photographs and geological maps, and use them to identify both modern and historical patterns of erosion and landscape modification; Understand the erosional processes that shape the Adelaide coastline, and their links to human activities such as housing development and waste disposal; Describe the various different management practices that are currently being implemented along the metropolitan coastline, and identify how engineering solutions need to take into account a range of coastal processes such as longshore drift and storm activity. INTRODUCTION Figure 1 is a schematic view of the Adelaide region. It shows the location of major fault structures such as the Eden and Para Faults, as well as the position of the modern shoreline. South of Kingston Park, the land has been uplifted by the Eden Fault and there is a series of coastal cliffs that extend several kilometres further south. To the north of Kingston Park, the coastline comprises essentially sandy beaches backed by a coastal dune system. These have been substantially modified since European settlement in 1836. Figure 1. Simplified block diagram of the Adelaide region, showing uplifted fault blocks and the position of the coast. H = Hallett Cove; K = Kingston Park; O = Outer Harbor. After Talbot & Nesbitt (1968). Engineering & Environmental Geology Page 2 Metro Beaches Background Info About 20 000 years ago, at the time of the last major ice age, sea level was about 130 metres lower than it is today due to the amount of water locked up in ice sheets, ice caps and glaciers. As the ice melted, sea level rose and reached its present level about 7000 years ago. There have been several important factors involved in the development of the Adelaide coastline (and other similar coastlines) since that time. These include: 1. South to north longshore drift (Fig. 2) caused by the prevailing southwesterly winds. It has been estimated that each year 40 000 to 70 000 cubic metres of sand passes any given point along the coastline. Any obstruction, such as a breakwater or groyne, will impede the progress of the sand and result in significant build-up on the ‘upstream’ side of the obstruction and a shortage of sand on the lee side. Figure 2. Longshore drift is caused by waves approaching the shore at an angle. The sand grains are swept obliquely forwards by the waves and then move at right angles to the beach in the backswash due to the influence of gravity. From Press & Seiver (1998). 2. Above the normal high tide mark, sand dries out during the day and onshore winds blow it inland, where it forms a coastal dune system (or a series of parallel dunes) that trend parallel to the shoreline. During storms, particularly if the storms coincide with a very high tide, there may be substantial erosion of the dune system, and the sand it contains will be transported into offshore bars. When normal weather resumes, the dunes will be re-established. Hence, the dunes act as a reservoir of sand for the beach. Figure 3 shows the profile of a sandy beach. Engineering & Environmental Geology Page 3 Metro Beaches Background Info Figure 3. Profile of a sandy beach. Note the presence of the dune system behind the beach. From Press & Seiver (1998). 3. There is a natural seasonal change in beach profile during the year (Fig. 4). In winter, the waves are bigger and have a shorter wavelength than those of the summer. The winter waves tend to be erosional, with sand being moved from the beach into a series of offshore bars. The summer waves tend to be constructional and move the sand from the offshore bars back up on to the beach. Figure 4. Seasonal variations in beach profile from Carmel Beach, California. Note that this is a northern hemisphere beach, and seasons are therefore opposite to the southern hemisphere. From Twidale (1973). Engineering & Environmental Geology Page 4 Metro Beaches Background Info 4. Posidonia australis is a densely growing seagrass that binds sand together in the shallow subtidal areas of Gulf St Vincent. There has been considerable loss of seagrass in near-shore parts of this region due to the discharge of metropolitan waste water into the sea (Fig. 5). Detailed surveying of near-shore areas that exhibit seagrass loss has shown that the substratum has been eroded by an average amount of one metre. This allows an increase of wave energy on to the coast and hence a rise in the velocity of longshore drift. It has been estimated that prior to European settlement, surface runoff to Gulf St Vincent was about 20 gigalitres per year. It is now approximately 120 gigalitres per year. Figure 5. Seagrass loss, Adelaide metropolitan coastline. From Harvey & Caton (2003). 5. There has been a rapid relative sea level rise in the Port Adelaide/Outer Harbor area of approximately 2.08 mm per year. However, it is estimated that local land subsidence in the same region accounts for about three-quarters of this relative sea level rise. Part of this subsidence is due to groundwater withdrawal. Further information on the Adelaide Metropolitan Coastline is available from the Department of Environment and Natural Resources at the following website: http://www.environment.sa.gov.au/our-places/coasts/Adelaides_Living_Beaches http://www.environment.sa.gov.au/our-places/coasts/Adelaides_Living_Beaches Engineering & Environmental Geology Page 5 Metro Beaches Background Info The sand management strategy for 2005‒2025 is summarised in Fig. 6. Further details about the sand pumping component of this strategy can be found here: http://www.environment.sa.gov.au/our- places/coasts/Adelaides_Living_Beaches/Sand_Transfer_Infrastructure_project Figure 6. Summary of proposed sand management strategy for Adelaide metropolitan beaches, 2005‒2025. (From Adelaide’s Living Beaches: A Strategy for 2005‒2025, DEWNR; http://www.environment.sa.gov.au/files/84d361f9-0231-4518-b73d-a0a100b5c0c3/con-gen-albstrategy.pdf). http://www.environment.sa.gov.au/our-places/coasts/Adelaides_Living_Beaches/Sand_Transfer_Infrastructure_project http://www.environment.sa.gov.au/our-places/coasts/Adelaides_Living_Beaches/Sand_Transfer_Infrastructure_project http://www.environment.sa.gov.au/files/84d361f9-0231-4518-b73d-a0a100b5c0c3/con-gen-albstrategy.pdf UNIVERSITY of SOUTH AUSTRALIA OPEN UNIVERSITIES AUSTRALIA ENGINEERING & ENVIRONMENTAL GEOLOGY (ENR120) Metropolitan beaches field trip assignment Your task is to virtually visit the Adelaide metropolitan coastline and investigate its record of modern and historical patterns of erosion and landscape modification. For one selected site along the coast, answer the following questions: 1. Provide historical evidence of the ways in which the environment at this site was significantly different to how it appears today. Describe the geological characteristics of this past environment that have since undergone modification, and support your statements using historical accounts, archival photographs or any other appropriate records. 10 marks 2. Provide your own observations (using satellite imagery) for current landscape modification issues at this site. Support your observations with maps, photographs or aerial imagery of key problems, and describe the major causes that have contributed to them. 10 marks 3. Discuss the current ways in which landscape modification is being managed at this site, and comment on the advantages and disadvantages of a range of solutions that could be implemented. You should consider their relative feasibility and sustainability, their economic and aesthetic impacts, and speculate on how engineering innovations or environmental initiatives might assist the management and preservation of Adelaide’s coastal environments. 15 marks Marks will also be awarded for presentation according to the scheme below: • Spelling, grammar, punctuation, sentence construction, report organisation 5 marks • Use of an appropriate and consistent referencing style – note that there is no need to reference lecture/practical notes or personal communications 5 marks This means there are 45 marks in total for this assessment piece. It counts for 10% towards the total course assessment. Please note that it must contain evidence that you have done the following: 1. Explored the web links provided in the Coastal processes practical handout and the learnonline website (e.g. flyers and reports available from the Department of Environment, Water and Natural Resources) and referenced these sources in your answers (see below); 2. Shown evidence for further personal research to substantiate answers provided to the three questions (i.e. do not just list references already given to you in lectures or background material – show evidence that you have undertaken your own research). 3. Used aerial photos available from Google Earth or other map providers (e.g. Bing Maps, ESRI, etc