Tsunami Building Damage in Seaside, Oregon
Stephen Duncan
& RJ Strength
Final Project
CE 202-003
March 13, 2009
http://web.engr.oregonstate.edu/~strengtr/
INTRODUCTION:
Tsunamis have been a widely discussed topic for the city of Seaside located on the Oregon Coast in recent years. It has been over 300 years since the last tsunami and there is a 1 in 7 chance that a large scale tsunami will occur in the next 50 years (Millstein). Many people are doing extensive research to minimize the effect the tsunami would have if it were to hit the Oregon coast. At the OSU wave lab, engineers are studying the effects that a tsunami would have on Seaside, OR. Elaborate evacuation routes have been designed to help as many people as possible escape to safety in the event that a tsunami was to occur. For our project, we wanted to look more into the details of what kind of damage the tsunami would cause. Since the likelihood of tsunami in the near future is very real, it would be helpful to know the extent of damage it would cause, and what it would take to rebuilt all the buildings the tsunami destroyed. For our GIS analysis, we are going look at data on possible tsunami wave heights and compare it to the layout of current structures. We will assume that the higher the wave height, the more the damage to the building. Our final data and maps will show how many buildings will be damaged and what percentage of damage each building will undergo.
SITE DESCRIPTION:
Since there is an abundance of data for tsunamis in Seaside, OR, we decided that Seaside would be the perfect area to do our tsunami analysis on. Seaside is located on the Oregon Coast in the northern part of the state. The size of the area we are investigating is 3.9 square miles (10.0 km2). Seaside has a large sandy beach that borders the ocean and the rest of the city is flat. The elevation is close to sea level for most of the city. The land near the ocean is sandy and lacks vegetation where as further inland, one can find lush forest land.
Screen Shot of Seaside relative to Oregon’s coastline
DATA:
http://www.oregon.gov/DAS/EISPD/GEO/alphalist.shtml#O Data type, Vector NAD_1983, UTM Zone 10, Meter Resolution 1:24,000
This is a file of the city limits in Oregon and this helped with the location of Seaside.
2. Wave Heights; USGS Web page http://pubs.usgs.gov/ds/2006/236/catalog.shtml Data type, Raster D_North_American_1983, Meter Resolution 1:30,000
This was a file that portrayed the height of waves along the shore of Seaside during the last 300 years. We used this to show what the tsunami might look like if it hits Seaside.
3. Buildings of Seaside; OSU Wave lab Source Tracy was able to find this from the research lab at OSU, Data type NAD_1983, UTM Zone 10, Meter resolution 1:30,000
This was a file that was given to us by the OSU wave research lab. This had all of the buildings of Seaside that were rendered off of goggle map through GIS. This contained the attributes, size, tax lot, location, and type of data (Polygon)
4. Shore Line, USGS web page http://pubs.usgs.gov/ds/2006/236/catalog.shtml#arcreader Data type Vector NAD_1983, UTM Zone 10, Meter Resolution 1:100,000
This was a GIS file that had an image of the Oregon and Washington coast line. This was used to aid us in better showing the damage area of where the tsunami would hit along the Seaside coast range.
GIS METHODS:
To start off our GIS analysis, we searched the web for Seaside Tsunami data until we found all the data we needed. Most of our data was obtained in this manner, except for the Seaside building data, which we obtained from the OSU wave lab via Tracy. We imported all four data sets (City Limits 2007, Wave Heights, Buildings of Seaside, and Shoreline) into ArcGIS and converted them to all have the same map projection: UTM zone 10 with datum of NAD 83. We reclassified the wave height data into just four categories: 0 damage, 30% damage, 55% damage, 85% damage, and 99% damage, with the percentage of damage being an estimate of how much damage the various heights of water would cause. We assumed 0 to 2.6 feet of water to cause no damage, 2.61 to 6.4 foot of waves would cause 30% damage, 6.41 to 8.5 foot waves would cause 55% damage, 8.51 to 10.34 foot waves would cause 85% damage, and 10.35 feet and higher waves would cause 99% damage to the building. We then converted the buildings from features to raster and input them into the raster calculator. We multiplied the buildings by the wave height raster to find the total number of buildings in each corresponding wave height category. We now have a dataset which states how many buildings were not damaged at all, damaged 30%, damaged 55%, damaged 85%, and damaged 99%.
OUTCOMES/RESULTS:
After conduction our GIS analysis, we came up with the results we were looking for. According to our map, 108 buildings lost 30% of their value, 518 buildings lost 55% of their value, 333 buildings lost 85% of their value, and 123 buildings lost 99% of their value. These results are shown in the chart below:
Number of Buildings in each Damage Category |
|
108 Buildings |
30 % value loss |
518 Buildings |
55 % value loss |
333 Buildings |
85 % value loss |
123 Buildings |
99 % value loss |
DISCUSSION:
While analyzing this scenario, we found the main outcome of a tsunami would be the failure of the buildings to withstand the force of the tsunami waves. While our damage percentages were just estimates, higher water would do significantly more damage. For future construction, in order to make the city of Seaside a safer place in the event of a tsunami, buildings need to be designed to be able to withstand the force of the water as well as be higher off the ground. The new buildings would not be affected so severely by the tsunami and the cost of repairs would greatly decrease. A tsunami is always going to cause a massive amount of destruction to any location it hits, but if the location was ready for it, and had as many tsunami proof buildings as possible, the path to recovery can be much shorter.
CONCLUSION:
Overall our group thought this project was a successful way to get students some hands on experience with GIS and really learn how to use the basics of the program. The project we chose was a difficult but accomplishable problem. The web had a lot of tsunami data that proved useful for our analysis of the city of Seaside. One challenging part of the project was getting a hold of the buildings of Seaside. We were fortunate enough to be able to get data from the OSU wave lab. With this data, we were able to show a GIS map of the damage a tsunami would do to Seaside Oregon.
It would have been nice if we could have started the project earlier in the term that way students can start to think about what they might want to do. Other than that, the project as a whole was very successful in teaching students how to find data off the internet and convert it into useful GIS information.
APPENDIX:
Bibliography
Bibliography:
Oregon Tsunami May Turn Out Bigger Than They Thought, by Michael Millstein
http://blog.oregonlive.com/pdxgreen/2008/03/oregon_tsunami_may_turn_out_bi.html
Cover page Picture
http://livesaildie.com/2007/04/tsunami-threat-to-eastern-australia/
OSU Wave Lab: Simulated Tsunami
http://wave.oregonstate.edu/news/story/2216
City of Seaside, Oregon Tsunami Education and Information
http://www.cityofseaside.us/tsunamiinfo/
USGS GIS data source
http://www.usgs.gov/
Oregon Geospatial Interface
http://www.oregon.gov/DAS/EISPD/GEO/alphalist.shtml#O
