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Dr. Greg Carter in the Department of Geography and Geology is leading the historical marsh change and mapping task. Ms. Heather Nicholson classified historical imagery (1955, 1992, 2014) for Grand Bay using textural analysis and Mrs. Margaret Bell Waldron did a similar classification on the Pascagoula River imagery (1955, 1979, 1996, 2014) using both textural and spectral (color-IR) information for their respective Master's thesis research. A GIS storymap is available describing the historical marsh change in the Pascagoula River Delta, MS.
Synopsis:
Existing aerial imagery going back to the 1940’s will be analyzed and classified (Fig. 1) using gray-scale brightness and texture analyses to determine historical marsh extent, composition, and fragmentation using semi-automated classification methods. We will (1) evaluate spatial statistics and texture indices derived from historical, vertical aerial photography, (2) use these statistical and textural parameters to produce a time-series of marsh extent in the general study areas, and (3) evaluate apparent changes in marsh extent over time. With appropriate analytical methods, such photographs can provide an invaluable source of information for assessing landscape and ecological change at high spatial resolution and decadal or finer temporal scales. Change in marsh through time will be determined by utilizing the well-established image subtraction, land-cover change detection procedures described in Jensen (2005). Changes in spatial distribution patterns as well as total coverage will be quantified for the decades prior to the availability of modern satellite data.
Figure 1: Classified images from 2014 showing the different habitat types in the Pascagoula river (left) and Grand Bay (right). Coastal salt marsh habitat was the area of interest for this research. Images are not to the same scale.
Grand Bay:
Coastal marshlands are among the world’s most highly productive ecosystems but they have diminished greatly in the past several decades owing to sea-level rise and direct anthropogenic influences. An effective means of quantifying loss or gain in marsh area is through the use of aerial image data, which offers synoptic views of the landscape at decadal-scale sampling frequencies. However, a potential problem with older panchromatic, or black- and-white, imagery is the absence of multispectral information that might be used otherwise in remote identification of vegetation types. Nevertheless, the analysis of horizontal variability in image brightness values, or image texture, can be used in deriving marsh areal coverage from even the oldest- available aerial photography. This project employed imagery acquired in 1955, 1992, and 2014 over Jackson County, Mississippi, to determine the extent of marshland loss or gain in the vicinity of the present-day Grand Bay National Estuarine Research Reserve (GBNERR). After pre-processing the images, image textural parameters were computed using the Grey-Level Co-Occurrence Matrix procedure (ENVI). A Maximum-Likelihood classification of the textural parameters to vegetation type was derived based on ground control point data. A change detection analysis then was applied among years. Preliminary results suggest that a net loss of around 5% in marsh area occurred in the GBNERR vicinity from 1955 to 2014. Results will assist resource managers in determining locations that may be most vulnerable to continued sea level rise and direct human impact.
Figure 2: Time series showing habitat change from 1955 to 2014 for Grand Bay. Green areas are coastal marsh.
Figure 3: Map showing change in the mid-region of GBNERR from 1955 to 2014. The red areas represent marsh loss, whereas the green areas represent marsh gain. Marsh loss occurred primarily due to edge erosion along the entire southern coastline with up to 490m of shoreline loss at South Rigolets Island (~8.3 m per year).
Nicholson_2017_TEXTURAL ANALYSIS OF HISTORICAL AERIAL PHOTOGRAPHY TO DETERMINE_AquilaPDF.pdfDownload a PDF copy of Ms. Heather Nicholson's MS Thesis on changes to coastal marsh habitat at Grand Bay.
Recommended Citation
Nicholson, Heather Michelle, "Textural Analysis of Historical Aerial Photography to Determine Change In Coastal Marsh Extent: Site of the Present-Day Grand Bay National Estuarine Research Reserve (GBNERR), Mississippi, 1955-2014" (2017). Master's Theses. 317. https://aquila.usm.edu/masters_theses/317
Pascagoula River delta:
As sea level rise accelerates, coastal marsh ecosystems are increasingly vulnerable. Vertical accretion rates must exceed or keep pace with rates of sea level rise to prevent transition to open water or inland migration of marsh vegetation. While some marsh systems along the northern Gulf of Mexico coast have remained stable, others, e.g., the marshes of the Louisiana Gulf Coast, have experienced high rates of conversion to open water. This study examined the historical extent of intertidal marsh at the mouth of the Pascagoula River in Jackson County, Mississippi to determine whether marsh extent changed during the period 1955-2014 and to ascertain rates of change. Marsh extent was mapped at 3 meters GSD using spectral and textural aerial image data for image dates of February 13, 1955 (black and white), February 12, 1996 (color-infrared), and October 5-16, 2014 (color-infrared). Waterways represented in the imagery were classified using a near-infrared band threshold for 1996 and 2014 and a CV-band threshold for 1955. Land cover was classified into three groups–marsh, woodland/shrubs, and unvegetated–using a Maximum Likelihood Classifier. Change detection analysis revealed a net marsh loss of 1314.4 ha (19.9%) between 1955 and 2014. Classified marsh extent decreased by 1068.3 ha (16.1%) between 1955 and 1996, and 246.1 ha (4.4%) between 1996 and 2014. Linear regression of marsh extent with year yielded a slope of - 22.9 ha/year with a coefficient of determination of r2 = 0.98. The results indicate that marsh extent will continue to decrease in the Pascagoula River Estuary.
Figure 4: Time series showing habitat change from 1955 to 2014 for Pascagoula River. Green areas are coastal marsh.
Figure 5: Map showing change in the Pascagoula River delta from 1955 to 2014. The red areas represent marsh gain, whereas the blue areas represent marsh loss (water gained).
Figure 6: Marsh loss occurred primarily due to edge erosion along the entire southern portion of the delta with up to 44m of shoreline loss at Twin Islands (~0.75 m per year).
Waldron_2019_Thesis.pdfDownload a PDF copy of Mrs. Margaret Waldron's MS Thesis on changes to coastal marsh habitat int the Pascagoula River.
Recommended Citations
Waldron, Margaret Claire Bell, "Detecting Coastal Marsh Change From Aerial Imagery Using Spectral and Textural Methods: Pascagoula River Estuary, Mississippi, 1955-2014" (2019). Master's Theses. 632. https://aquila.usm.edu/masters_theses/632
Waldron, M.C.B.; Carter, G.A., and Biber, P.D., 2021. Using aerial imagery to determine the effects of sea-level rise on fluvial marshes at the mouth of the Pascagoula River (Mississippi, U.S.A.). Journal of Coastal Research
https://doi.org/10.2112/JCOASTRES-D-20-00037.1
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