Abstract:

This study mapped land cover (vegetation, sand, and water) from the western portion of the Colorado River Delta through the eastern portion of Matagorda Island, TX, over fourteen imagery dates (1850s, 1930s, 1943, 1953, 1972, 1981, 1995, 2001, 2004, 2009, 2012, 2015, 2018, and 2020). Vegetation width, beach width, and total land width (vegetation width and beach width combined) were also calculated every 20 m. The data was created for the Texas Office of the Comptroller project titled “Matagorda Bay Ecosystem Assessment”. The data package contains 58 files. Land cover/habitat maps for 2012-2013 are available in related dataset HI.x833.000:0021 (https://doi.org/10.7266/ex6xqek7).

Suggested Citation:

Magolan, Jessica, Lihong Su, and James Gibeaut. 2024. Mapping land cover area and width from 1850-2020 within West Matagorda Bay, Texas. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/zs2f74bj

Purpose:

This dataset was developed within the Harte Research Institute for Gulf of Mexico Studies (HRI) for the project titled "Matagorda Bay Ecosystem Assessment" in order to assess long-term habitat changes since the mid-1800s.

Data Parameters and Units:

area [square meters]; length [m], BaselineID (correlates study area section and baseline ID section from DSAS); TransOrder (transect data ordered alongshore from baseline start to baseline end); Order_CRD (position of each transect from the mouth of the Colorado River, [enum]); Distance_C (distance of each transect from the mouth of the Colorado River, [m])

Methods:

IMAGERY SOURCES Fourteen imagery dates (1850’s, 1930’s, 1943, 1953, 1972, 1981, 1995, 2001, 2004, 2009, 2012, 2015, 2018, 2020), originating from a variety of sources (NOAA T-Sheets, Aerial Photo Single Frames (ASPF), National High-Altitude Photography (NHAP), Texas Orthoimagery Program (TOP), and National Agriculture Imagery Program (NAIP)), with varying spatial and spectral characteristics were used to map land cover. Details regarding where to obtain the imagery sources used is addressed within the data package. However, the imagery date, spectral resolution, and spatial resolution (m) are presented below: • 1850's - BW - N/A • 1930’s - BW - N/A • 1943 - BW - 1 • 1953 - BW - 2 • 1972 - CIR - 3.25 • 1981 - CIR - 1.6 • 1995 - CIR - 1 • 2001 - CIR - 1 • 2004 - CIR - 1 • 2009 - CIR - 0.5 • 2012 - RGBN - 1 • 2015 - RGBN - 0.5 • 2018 - RGBN - 0.6 • 2020 - RGBN - 0.6 Twelve of the sources (1943–2020) consisted of aerial photography while 1850’s and 1930’s were NOAA T-Sheets. Imagery from 1943–2001 required rectification while 2004–2020 came rectified. The six unrectified aerial photography sources were rectified in ArcMap 10.8 to 2016 National Agriculture Imagery Program (NAIP) orthorectified aerial photography (using Universal Transverse Mercator (UTM) coordinate system, North American Datum (NAD) 83). Additionally, to cover the entire study area, multiple images for each timeframe were required, and after rectification images were mosaicked together. For the 1850’s and 1930’s NOAA T-Sheets, each T-Sheet consisted of a compilation of years and resultingly the 1850’s data is from 1855–1859 while the 1933 data is from 1933, 1934, and 1939. MAPPING LAND COVER After rectifying and mosaicking imagery together, all twelve years of imagery (1943 through 2020) were manually digitized in ArcMap 10.8 and then classified using visual inspection. The map scale of digitization varied depending on the spatial resolution. Digitized polygons were classified into three land covers: vegetation, sand, and water. After digitization and classification were complete, the data were1) smoothed using the "Smooth" tool with 2 m Paek to get rid of jagged edges, and 2) checked for topological errors to ensure there were no overlapping features or gaps in the data. The 1850’s and 1930’s NOAA T-Sheets required a slightly different workflow. The vectorized shoreline delineated the land/water boundary and the georeferenced T-Sheet distinguished vegetation, water, and sand based on textural differences. Both files were used concurrently to digitize the Gulf vegetation line and this boundary was incorporated into the vectorized shoreline, resulting in the same land cover classifications (vegetation, sand, water) that were obtained from the aerial photography. VEGETATION WIDTH, BEACH WIDTH, & TOTAL LAND WIDTH Spatial patterns were further analyzed in terms of width at the transect level. First, the Digital Shoreline Analysis System (DSAS) was used to generate a baseline parallel to the coastline and transects were generated every 20 m perpendicular to the baseline resulting in over 2,000 transects. The transects were then clipped to the vegetation, Gulf beach, and land extents. Any vegetation patches present within the Gulf beach were included in the Gulf beach width. Non-Gulf beach sand, predominately located along the bay shoreline, was included in the vegetation width. The land width was then calculated as the combined width of the island, comprising both the Gulf beach and vegetation width.

Provenance and Historical References:

Strategic Mapping Program. (1996). Texas 1996 TOP Imagery. Retrieved from https://data.tnris.org/collection?c=85d8fb09-cc72-442f-9b44-287ed8079dbc#4.45/31.34/-100.09 Strategic Mapping Program. (2009). Texas 2009 TOP Imagery. Retrieved from https://data.tnris.org/collection?c=e8a9bba2-b219-47a7-be04-ff6493363c27#5.93/29.732/-96.062 Texas General Land Office. (2001). 2001 Aerial Imagery. Retrieved from November 20/December 14, 2001. https://www.glo.texas.gov/land/land-management/gis/aerials/matagorda11-30-01/index.html TNRIS. (2015). Texas 2015 TOP Imagery. Retrieved from https://data.tnris.org/collection?c=b7e5b638-99f0-4676-9411-c88d06d49943#4.45/31.31/-100.12 U.S. DOC, NOAA, NESDIS, and NOS. (2016). NOAA Historical Surveys (T-Sheets). Retrieved from NOAA Shoreline Website. https://shoreline.noaa.gov/data/datasheets/t-sheets.html USDA. (1953). Matagorda 1953 USDA Historic Imagery. Retrieved from TNRIS DataHub. https://data.tnris.org/?pg=2&inc=24&s=matagorda&category=Imagery USDA. (1943). 1943 Matagorda County Aerial Imagery. Retrieved from https://www.glo.texas.gov/land/land-management/gis/aerials/1940s/matagorda/index2.html USDA. (2004). Texas 2004 NAIP Imagery. Retrieved from https://data.tnris.org/collection?c=a8756dac-62a7-4b51-8d07-ab0cecb6e600#4.96/31.31/-100.09 USDA. (2012). Texas 2012 NAIP Imagery. Retrieved from https://data.tnris.org/collection?c=924d3c6f-9f74-4147-8044-d4025f12eac3#4.45/31.46/-100.09 USDA. (2018). Texas 2018 NAIP Imagery. Retrieved from https://data.tnris.org/collection?c=f1d66250-4021-47df-9fe9-9fca286b0f50#4.45/31.41/-100.12 USDA. (2020). Texas 2020 NAIP Imagery. Retrieved from https://data.tnris.org/collection?c=aa5183ca-a1bd-4b5f-9b63-4ba48d01b83d#5.5/31.33/-99.341 USGS. (1972). Aerial Photo Single Frame. Retrieved from https://earthexplorer.usgs.gov/ USGS. (1981). National High Altitude Photography. Retrieved from https://earthexplorer.usgs.gov/

Individual Files: