Lab 8 coastal hazards and floods - Google Docs

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University of Arkansas, Little Rock *

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1104

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Geography

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Oct 30, 2023

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pdf

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Uploaded by BrigadierKouprey15497

Open up the ArcGIS Webmap: Lab 8 - Coastal Hazards . In the upper left corner, type in La Conchita, CA In the webmap, the large pink rectangle has the Measurement tool and the Basemap Gallery. Click on these tools to learn how to use them (or watch the introduction video for Lab 8). The search bar is in the upper left corner. The scale bar is in the lower left corner. Investigate this webmap by turning on and off the Imagery, Topographic, Streets, and World Hillshade basemaps. View this area at differing scales (between 200 feet and a scale of 4 miles). Observe the topography of the land, the shoreline shape, and the beaches for this site. #1 While viewing the Imagery, zoom in (scale bar = 200 feet) and use the Measurement tool to measure the width of the beach in front of La Conchita, CA (from the highway to the water line). Record your width in meters . About 102 meters Would this be classified as a wide or narrow beach? Narrow #2 Zoom out to where the scale bar at the bottom of the map shows ~0.3 miles. Use the Measurement tool to measure the length of this beach (roughly north-south). Record this length in kilometers . 1.39 km, maybe more toward 2km Zoom out to ~2 miles. At this scale, is this coastline smooth or irregular ? It looks irregular #3 Based on the observations you just made, which type of shoreline is this ( active vs. passive )? Active Is this location along a tectonic boundary? If so, what type of boundary is it? It is on the San Adreas fault which is a transform plate boundary #4 La Conchita was established as a modern village in 1924. Why do you think people built a community of houses here at this location? I think it is a great place to live scene wise. The beach was untouched at that time and I know people had to be drawn to the beauty of that

#5 Based on Lab 7 (Mass Wasting), we know that landslides are a hazard at this location. Human activity DID contribute to the past landslides at La Conchita, CA. However, imagine if the village and the highway did not exist. What coastal processes would contribute to slope instability here? (hint: what repetative coastal processes would be concentrated where these steep slopes meet the ocean in the absence of the village and highway?) Waves and near-shore currents would definitely change the land. The process of hydraulic action would take place here. I also read that the sediment there is poorly indurated, affecting the slope. Location 2: Ocean City, MD Open up the ArcGIS Webmap: Lab 8 - Coastal Hazards . In the upper left corner, type in Ocean City, MD Investigate this webmap by turning on and off the Imagery, Topographic, Streets, and World Hillshade basemaps. View this area at differing scales (between 200 feet and a scale of 4 miles). Observe the topography of the land, the shoreline shape, and the beaches for this site. #6 While viewing the Imagery, zoom in (scale bar = 200 feet) and use the Measurement tool to measure the width of the beach just north of the fishing pier (from the road to the water line). Record your width in meters . 116 meters Would this be classified as a wide or narrow beach? Wide #7 Zoom far enough out (~6 miles) to use the Measurement tool to measure the length of this beach from the southern tip of Fenwick Island to the Indian River Inlet (to the north). Record this length in kilometers . 20 km At this scale, is this coastline smooth or irregular ? Smooth #8 Based on the observations you just made, which type of shoreline is this ( active vs. passive )? Passive Is this location along a tectonic boundary? If so, what type of boundary is it? No

#9 This area of Maryland was settled by European colonizers in the 17th century. Why do you think these people settled in this location? They were looking for flat and open land. This area's coastal shore line is also so smooth I figure that was enticing for colonists. #10 Based on what you know from previous labs, and about active and passive coastlines, are landslides a potential hazard in this location? Why or why not? No. The land is so flat on this coast I dont see landslides happenig there. #11 Based on the location of this area on the east coast of the United States, it has and is very likely to experience hurricane-related hazards. What is the recurrence interval for all hurricanes (category 1-5) for the Ocean City, MD coastal area? Refer to Figure 8.7 in the introductory materials. 105 Location 3: Chetco Point, Brookings, OR Open up the ArcGIS Webmap: Lab 8 - Coastal Hazards . In the upper left corner, type in Brookings, OR Investigate this webmap by turning on and off the Imagery, Topographic, Streets, and World Hillshade basemaps. View this area at differing scales (between 200 feet and a scale of 4 miles). Observe the topography of the land, the shoreline shape, and the beaches for this site. #12 While viewing the Imagery, zoom in (scale bar = 300 feet) and use the Measurement tool to measure the width of Mill Beach in Macklyn Cove (from the vegetation to the water line). Record your width in meters . 54 meters Would this be classified as a wide or narrow beach? narrow #13 At the same scale as for question #12, use the Measurement tool to measure the length of this beach (roughly east-west). Record this length in kilometers . About .5 km Zoom out (scale = 1 mile). Is this coastline smooth or irregular ? Irregular #14 Based on the observations you just made, which type of shoreline is this ( active vs. passive )? Active

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Is this location along a tectonic boundary? If so, what type of boundary is it? Convergent plate #15 This area of Oregon was inhabited by the Chetco tribe of Native Americans who first settled there between 1000 and 3000 years ago. Why do you think these people settled in this location? #16 Based on what you know from previous labs, and about active and passive coastlines, are hurricanes a potential hazard in this location? Why or why not? No. I read that the water temperate there is not warm enough for hurricanes. They are impacted by heavy rain but not the actual hurricane. Part 2 – Shoreline Retreat and Human Disruption as a Hazard For questions #17-20, refer to images in the introductory material as well as the Google Drawing file Lab 8 - Ocean City Map . This location is an example of when humans disrupt the natural balance of inputs and outputs, resulting in negative effects to natural features and human-built structures and infrastructure. #17 Using the Lab 8 - Ocean City Map , determine the number of meters that Assateague Island has retreated landward from 1933 to 1972 for both points X and Y. Recall, there are 1000 meters in 1 kilometer. Distance between points X and X' .5 km Distance between points Y and Y ' .7 km #18 First, calculate the retreat rate (i.e., velocity) in meters per year at both points X and Y. Remember that velocity equals distance divided by time. What is the time difference between the two positions? 39 years

What is the retreat rate for point X? 0.012 What is the retreat rate for point Y ? 0.017 #19 Next, find the average of your two retreat rates from above to calculate the average retreat rate for Assateague Island. Average retreat rate = 0.02 #20 Finally, based on your average retreat rate from above, how much farther should Assateague Island have migrated since the creation of the map in 1972 (50 years later)? Total additional retreat distance = BON US (2 points ) Using the points Z and Z' on the Lab 8 - Ocean City Map , how does the distance between the landward side of Assateague Island and the mainland in 1972 compare to the distance between similar points today (use the Webmap and the Measurement tool)? Does this distance support your answer from #20? If not, suggest a reason (or reasons) why these distances are not consistent.