Week 5: Data Analysis

Hi guys, welcome to Week 5. This week I will be sharing some of the data I have observed and will be collecting this week. My analysis will entail the studying of a few articles and data from the textbook Environmental Research Letters, more specifically these articles Modelling sea level rise impacts on storm surges along US coasts and Tidally adjusted estimates of topographic vulnerability to sea level rise and flooding for the contiguous United States by Claudia Tebaldi, Benjamin H Strauss, and Chris E Zervas.

Based on the National Research Council’s mid-range Pacific coast sea level rise projections, it is projected to rise 3 feet locally by 2100, from a 1992 baseline. The analysis translates this to 29 percent multi-year risk of at least one flood exceeding 3 feet from 2016 to 2030, a 91 percent risk from 2016 to midcentury, and a 100 percent risk by 2100. Under the Council’s high-end projections, these chances increase to 44, and 100 percent, respectively, and there exists a 100 percent change of a flood exceeding 6 feet. 

To better understand the exposure to sea level rise and flood, we must utilize a good map software. By combining tidal elevation models and lidar-based (laser-based) elevation data from the NOAA (National Oceanic and Atmospheric Administration) and levee location data from FEMA, we can identify both fully exposed and potentially protected land less than 1-10 feet above the local high tide line. The various exposure values show what is on the land below the selected water level or elevation using computing for any protection and without. It depicts general exposure for future sea level rise or flooding but not actual damage. Complications arise from protection, the bathtub method, elevation errors, data limitations, dynamics, and feature representation. Protection includes criteria, such as levees, walls, dams, ridges, or other features that may protect and safeguard some areas. An example would be block hydrologic connectivity at lower elevations, such as 10-year flood heights. Data limitations include incomplete levee data and elevation data that may not capture narrow seawalls, which results in a harder assessment of protection. The online tool included does allow for exclusion or inclusion of protected areas for analysis. If I am assessing protection, I will assume levees are always sufficiently tall and well built because data on height and condition are not available. However, I am assuming that these structures will not be sufficient, which is the point of this project to raise awareness and bring attention to mandating the structures and defense mechanisms to be enacted. The bathtub method involves employing elevation relative to local high tide lines (MHHW) by using near-flat water surfaces statewide to compare exposure. Future storms due to temperature changes may create uneven flooding in limited areas as well. Elevation error is accounted for by laser-based (“lidar”) data. Localized error could cause large low-lying areas to be mistakenly connected or isolated from the ocean at certain water levels. Dynamics, such as future erosion, marsh migration, coastal development and defense, or other dynamic factors affecting exposure, are not accounted for, but it is still an important factor to consider. These will be discussed in my paper for this week and how external dynamics are one of the underlying causes to our safety and impose risk. 

https://ibb.co/nbDCTCL

To give some awareness to the severity of the risk posed at 6 feet, we can observe this chart. At 6 feet, 13,276 people (1.6 percent of the total population in San Francisco) and $10,845 million are exposed in total.

Now this chart examines the observed water levels at a station near Candlestick Point Recreation Area. Flood maps are based on NOAA-supplied lidar elevation data and achieve near-perfect consistency with NOAA’s Sea Level Rise and Coastal Flooding Impacts Viewer over the two products’ shared elevation range (1-6 feet MHHW). The analysis adds elevation data from USGS to fill rare gaps or to make rare updates after newer lidar data become available. From this observed data, I have determined that throughout the time I have visited, water levels have indeed risen. On March 12, the observed water level was 0.19 ft, but the most recent data I have visited on March 26, shows an increase of 0.12 ft to 0.31 ft. Though it has rained and the temperature is warmer, we are observing a steady increase in water depth.

As I approach the midpoint of my project, I will be showcasing my field data next week, so we can compare my field work to available data and information in my paper. This will be important as it will be a good indication of what is occurring in our bay and perhaps the world. Until next time, thank you for reading my blog.

Sources:

Surging Seas Risk Finder: https://riskfinder.climatecentral.org/place/san-francisco.ca.us?comparisonType=place&forecastType=NOAA2017_int_p50&level=6&unit=ft

Surging Seas Risk Zone Map: https://ss2.climatecentral.org/#9/37.7186/-122.3863?show=satellite&projections=0-K14_RCP85-SLR&level=6&unit=feet&pois=hide

Strauss, B. H., Ziemlinski, R., Weiss, J. L., & Overpeck, J. T. (2012). “Tidally adjusted estimates of topographic vulnerability to sea level rise and flooding for the contiguous United States.” Environmental Research Letters, 7(1), 014033.

Tebaldi, C., Strauss, B. H., & Zervas, C. E. (2012). “Modelling sea level rise impacts on storm surges along US coasts.” Environmental Research Letters,7(1), 014032.