Abstract:

The shoreline of the Texas Coast was digitized and classified at a scale of 1:1,000 to create an environmental sensitivity index (ESI) dataset. The shoreline was mapped using a bare-earth 2m DEM created with LiDAR collected between 2007–2019, NAIP 60cm imagery collected in 2020, low-altitude oblique aerial photography accessed through EagleView, and ground-checking in the field.

Suggested Citation:

Magolan, Jessica, Rhiannon Bezore, Pu Huang, and James Gibeaut. 2024. Environmental Sensitivity Index (ESI) of the Texas coast using 2020 imagery. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/1v32bc5n

Purpose:

This dataset was developed within the Harte Research Institute for Gulf of Mexico Studies (HRI) for the Texas General Land Office (GLO) Oil Spill Prevention & Response Program, contract #22-005-003-D092 to create up-to-date ESI classifications of the Texas coast. For oil spill response purposes, shorelines are classified according to ESI rankings, which describe the sensitivity of the shore to oil as well as the difficulty and impacts of cleanup activities. Texas and federal partners use the ESI shoreline information to develop contingency plans for protecting the most sensitive environments and to help direct the deployment of limited resources during a spill.

Data Parameters and Units:

Shape_Length - length of feature in meters ESI - Concatenation of the ESI_1, ESI_2, and ESI_3 fields ESI_1 - Environmental Sensitivity Index Code 1 ESI_2 - Environmental Sensitivity Index Code 2 ESI_3 - Environmental Sensitivity Index Code 3 ESI_CRIT - The most environmentally sensitive ESI ranking specified in ESI_1, ES2_2 and ESI_3. Higher ESI numbers represent more sensitive shoreline habitats, and low numbers represent less sensitive habitats, therefore, the ESI_CRIT value is the highest ESI value from ESI_1, ESI_2, and ESI_3.

Methods:

Shoreline Delineation: To create the ESI shoreline dataset, the shoreline was manually digitized using a high-resolution Wacom interactive pen display tablet and ArcGIS 10.0 on a high-end workstation with multiple large, high-resolution displays. The shoreline was mapped at a maximum scale of 1:1,000, with some regions requiring a scale of 1:500–1:800 for more detailed digitization, from 2020 NAIP 60 cm natural-color ortho imagery obtained from the Texas Natural Resources Information System (TNRIS). The shoreline was then dissolved into single-part polylines and checked for topological errors. Shoreline Classification: The entire length of the digitized shoreline was classified with ESI values in accordance with the ESI scheme (see table below). The shoreline ESI classifications were determined by expert interpretation of the following sources: (1) 2020 NAIP imagery; (2) 2009–2021 low-altitude oblique and orthometric aerial photography from EagleView; (3) 2009–2021 Google Earth satellite imagery; (4) National Wetland (NWI) classifications from the U.S. Fish &Wildlife Service; (5) 2005 geologic map database of Texas to differentiate between clay scarps and sand scarps; and (6) field observations. Shoreline-type interpreters used high-end GIS workstations with large, high-resolution displays to view the multiple imagery sources simultaneously for a single area. Shoreline features with a length of 3 m or greater were captured in the classification. Along many segments of the Texas coast, several shoreline types occur in close proximity in a direction normal to the shoreline, and therefore several ESI rankings are assigned to a shoreline segment where multiple shoreline types are subject to oiling. During the classification process, each length of shoreline was assigned one, two, or three ESI rankings depending on how many habitat types existed in proximity to the shoreline in that area. Five fields were ultimately used to store these shoreline types: ESI, ESI_1, ESI_2, ESI_3, and ESI_CRIT. The first ranking was stored in the ESI_1 field, the second ranking (if assigned) was stored in the ESI_2 field and the third ranking (if assigned) was stored in the ESI_3 field. If more than one ranking was assigned, the ESI_1 value always represented the most landward habitat, and each additional ranking was situated progressively seaward. Similarly, the ESI field consisted of a list of the one, two, or three ESI rankings indicated in the ESI_1, ESI_2, and ESI_3 fields and was listed as moving from the most landward shoreline type to the most seaward. The ESI_CRIT field represented the most critical shoreline type that could be damaged or destroyed due to an oil spill. Field Verification: Field verifications were performed to aid in classification. The ESI rankings and boundaries were spot checked by boat and from land. Areas were targeted that required additional information due to complexity of shoreline types, significant changes in shoreline types, and for calibration of aerial imagery. In cases where the imagery and groundtruth classifications differed or no recent imagery was available, the shoreline classification was changed to the field verified shoreline type. Data Sources: 2020 NAIP imagery: https://naip-image-dates-usdaonline.hub.arcgis.com/datasets/58b70de9146c4bfda095f0a7acd563d4_0/explore?location=29.921290%2C-100.093750%2C6.10 NWI classifications: https://www.fws.gov/program/national-wetlands-inventory/download-state-wetlands-data 2005 geologic map database of Texas: https://pubs.usgs.gov/ds/2005/170/downloads/

Individual Files: