Analysis of Tidal Water Elevations of An Individual Water Level Recorder for Salt Marsh Monitoring

Authors: Grant McKown (james.mckown@unh.edu), Jennifer Gibson (jennifer.gibson@unh.edu)

Organization: Coastal Habitat Restoration Team, Jackson Estuarine Laboratory, University of New Hampshire

Purpose:

The R project was created to expedite the analysis of tidal water elevation - time series data. The package calculates common tidal hydrology metrics (mean low tide, high tide, etc.) and flooding parameters for given elevations of the salt marsh surface (flooding duration, high tide fooding frequency, etc.) for a single water level recorder over 30 days (single lunar cycle). The R project is designed for the water level recorder to have been deployed in a creek, ditch, or other hydrologic pathway that captures the local tidal hydrology. The R package is not designed nor appropriate for the analysis of a groundwater level recorder

Any user is free (and encouraged!) to download and use the R project. Note of Warning - the code may be updated from time to time to ensure compatibility with R package updates and enhance capabilities.

Monitoring Design Requirements:

The R code is specifically written to meet the then needs of broad hydrology monitoring protocols for salt marshes and coastal wetlands. The code is built on the R package 'VulnToolkit' by Troy Hill (https://cran.r-project.org/web/packages/VulnToolkit/index.html), which was specifically designed to help identify low and high tides and calculate flooding frequency and durations for given elevations. The R project is a wrapper for the 'VulnToolkit' to quickly analyze single water level recorders and calculate flooding statistics for given elevations. Additionally, the R package creates a nice graph with the ggplot2 package of the continuous water level elevation time series.

Project Overview:

A brief description of the five R code scripts is provided:

1. Format Dataset - R script formats the water level elevation - time series dataset to allow for use in the rest of the R scripts

2. Tidal Hydrology Statistics - R script calculates mean low tide, high tide, higher high tide, and maximum tide elevation for the water level recorder

3. Flooding Statistics - R script calculates flooding duration (% of monitoring time) and high tide flooding frequency (%) for given elevations based on the water level recorder time series dataset.

4. Graphing Tidal Elevations - R script graphs the continuous tidal water elevations over the 30 day study period (single lunar cycle) as well as reference lines for the marsh platform and root zone elevations.

Date Input Requirements:

For the R project, only two datasets, in CSV format, are required:

(1) Water Level Elevation Time Series - the continuous water level recorder dataset. The datset only has two columns:

• Date.Time = Date and Time of each water elevation measurement. Date and time column must be in the format of 'Month/Day/Year Hour:Minute'. Example: 12/5/2024 12:15. Time must be formatted in military time (e.g., 24 hour format).

• WLR = water elevation measurements. Units are at the discretion of the user.

See the Dataset Templates folder for an example.

Folders:

See individual README files in each folder for more in-depth details.

1. Input Data - folder the user of the R project will need to deposit the necessary datasets. See the folder README for in-depth details on the dataset needs for the R scripts. Example datasets are provided in the folder. R script is currently written to run with the example datasets.

2. Dataset Templates - blank CSV files with appropriate column headers (and blank cells) for the needed input datasets

3. Formatted Datasets - an intermediary folder that holds various water level elevation datasets that are created in one R script and utilized in the another R script'

4. Output Stats - destination of finalized tables for the descriptive statistics of tidal hydrology of creek, groundwater, and pool water level recorders and flooding for groundwater level recoders and constructed sparrow islands.

5. Figures - output of water level tidal elevation graphs in JPG format