Ph.D. Project Work

Overview

DELINEATING COSTAL SUBMERGENCE ALONG THE U.S. COASTLINE

Global sea level has been rising over the past century and the rising rate has increased in recent decades because of global warming. Sea level plays a critical role in wetland loss, coastal flooding, shoreline erosion, and flooding hazards from storms. In the long term, rising sea level also creates stress on groundwater systems and coastal ecosystems. As the sea-level rises, saltwater intrudes into freshwater aquifers, many of which sustain coastal ecosystems and provide water for municipal and agriculture use.

Sea level is primarily measured using tide gauge stations along the coasts and satellite laser altimeters. The Center for Operational Oceanographic Products and Services (COOPS) at National Oceanic and Atmospheric Administration (NOAA) operates the tide gauge stations along the west coast. In total, there are 28 tide gauge stations along the west coast of the U.S in this study. These measurements are monthly averages, which removes the effect of higher frequency phenomena to compute an accurate linear sea-level trend.

Instead of measuring ABSOLUTE sea-level changes, tide gauge measurements provide information on RELATIVE sea-level changes. This is because tide gauges measure sea levels relative to reference benchmarks fixed on the local land surface through repeat leveling surveys. This project uses tide gauges information relative to GPS stations with continuous daily sampling.

Approach

  • Research and compile list of Tide Gauges from National Oceanic and Atmospheric Administration (NOAA).
  • Research and compile list of GPS Stations from Nevada Geodetic Laboratory (NGL) and UNAVCO.
  • Collect Tide Gauge data from NOAA API.
  • Collect GPS Station data from UNAVCO API and NGL website using scrape script.
  • Process GPS data from both UNAVCO & NGL and plot in ArcGIS. The dataset contains 17,586 stations worldwide.
  • Compile list of GPS stations closest to Tide Gauges stations. Collect time series data for each of the stations.
  • Review and standardize dataset, converting time series data from m to mm.
  • Plot time series data for each Tide Gauge and GPS station.
  • Calculate absolute sea level using the rate of vertical movement from Tide Gauge and GPS datasets.

 

Tide Gauge Example

Below is an example of a typical Tide Gauge.

GPS Station Example

Below is an example of a typical GPS Station.

Tide Gauge & GPS Station Example

Below is an example of a typical Tide Gauge and GPS Station together.

Data

Data Retrieval Methods and Storage:

  • GPS Station and Tide Gauge data was collected using free public APIs located at NOAA.gov and UNAVCO.com
  • GPS Station data was also obtained from the Nevada Geodetic Laboratory (geodesy.unr.edu) website.
  • API data collection and website scrapes were performed by using SQL scripts and stored within a Microsoft SQL database

 

Additional Data Retrievel and API information:

 

The following technology tools were used in this project:

  • ArcGIS - Geographic Analytics & Mapping
  • Microsoft SQL (Version 2016) - Data Repository & API Data Retrieval
  • CoStat/CoPlot - Statistics & Graphs
  • Excel - Review & Analyze Datasets

 

Database Scripts - Microsoft SQL

Download Database Scripts: JWelch_EWCoast_Database_Scripts.zip

Below is a list of the database scripts included in the download.

 

Process GPS Data Script

Below is a snipet example of the SQL script used to retrieve the GPS Station data.

 

Process Tide Data Script

Below is a snipet example of the SQL script used to retrieve the Tide Gauge data.

Maps

By Jennifer Welch

West Coast Tide Gauges

This map shows where the Tide Gauges are located off the West Coast of the United States.

By Jennifer Welch

West Coast NGL vs UNAVCO GPS Stations /w Tide Gauges

This map shows GPS Stations from both the NGL & UNAVCO datasets and Tide Gauges off the West Coast of the United States.

By Jennifer Welch

West Coast GPS Stations & Tide Gauges

This map shows where the GPS Stations and Tide Gauges are located off the West Coast of the United States.

By Jennifer Welch

North Spit Tide Gauge & P162 GPS Locations

This map shows where the North Spit Tide Gauge and P162 GPS Station are located in reference to each other.

By Jennifer Welch

West Coast Relative Sea Level Rise

This map shows the West Coast Relative Sea Level Rise.

By Jennifer Welch

West Coast Absolute Sea Level Rise

This map shows the West Coast Absolute Sea Level Rise.

Graphs

TIDE GAUGE GRAPHS

GPS STATION GRAPHS

Results In Progress

Absolute sea level was calculated using Tide Gauges and GPS stations along the West Coast. Relative sea level rise is minimal in the upper north west coast at places such as Neah Bay with -2-0 mm/year sea level fall. However, when the nearest GPS velocity is considered for the vertical land movement the absolute sea level rise for Neah Bay was higher at 5-40 mm/yea sea level. San Diego remains the area with the highest relative and absolute sea level rise.