Clare Entwistle Urban Riparian Symposium 2017
Background: Coastal Wetlands Wetlands found in coastal watersheds: tidal and non-tidal wetlands are included Coastal Wetlands offer several important ecological services Texaswetlands.org houstonchronicle.com
Background: Historical Trends 41% of people worldwide live within 100 km of the coast (Martinez et al. 2014). 1996 – 2011 estimates the US lost 1,500 sq. mi. (960,000 acres) of coastal wetlands (Dahl and Stedman, 2013). 70+% were in watersheds surrounding the Gulf Coast (Diffenderfer, 2014). 25%-50% of the world’s coastal wetlands have been converted for anthropogenic uses (Bao, 2015).
Study Purpose What is the current state of wetland acreage in Galveston and Cameron County? Use aerial photography and online databases to map wetlands. Both pictures from: Texaswetlands.org
Two Study Areas Galveston County Cameron County Northern Coast Southern Coast Galveston Island South Padre Island $4.2 billion SPI receives more generated to Texas than a million economy through visitors annually travel 33% Texas Shrimp 1/3 of Texas Industry commercial fishing Port of Brownsville Over half of Eco-tourism recreational fishing
National Land Cover Database Provides Spatial reference and specific data for a variety of land covers 16 different land cover classes Years 2001, 2006, and 2011 Combined with: • NOAA C-CAP • USFWS NWI
Simplified Classification System 2001 Galveston County 2011 Cameron County
Quantifying Losses & Gains Raster Calculator was used for change detection: no change, conversion to upland, conversion to open water. 2001 – 2006 and 2006 – 2011 Calculated percent change
Accuracy Assessments Performed in ArcGIS 10.3 and Microsoft Excel Aerial Photography acquired from the National Agricultural Imagery Program (NAIP) – 2004, 2006, 2012 30 points for each classification – 90 total Confusion Matrix was generated: Kappa coefficient, overall accuracy, errors of commission, errors of omission, producer accuracy, and user accuracy.
Accuracy Assessments
Issues with NAIP Imagery 2006 Galveston County 2006 Cameron County
Results
Overall Gains and Losses: Galveston County Land Cover % Change 2001- % Change 2006- 2006 2011 Upland 4.47% 2.84% Wetland -4.59% -5.10% Open Water -1.15% -0.29%
Overall Gains and Losses: Galveston County Conversion Type 2001-2006 acreage 2006-2011 acreage Wetland to Upland 10562.82 11213.32 Wetland to Open 1441.34 2054.70 Water Upland to Wetland 5644.58 7711.51 Open Water to 2445.89 1541.19 Wetland
Overall Gains & Losses: Galveston County 2001-2006 Galveston County Land Change 2006-2011 Galveston County Land Change
Wetland Gains: Galveston County (2001-2006)
Galveston County Gains 2001-2006 - Close Up
Wetland Loss: Galveston County (2001-2006) League City
Galveston County Losses 2001-2006 – Close Up
Wetland Gain: Galveston County (2006-2011)
Wetland Loss: Galveston County (2006-2011) Dickinson & La Marque
Galveston County Losses 2006-2011 – Close Up
Overall Gains & Losses: Cameron County Land Cover % Change 2001- % Change 2006- 2006 2011 Upland -1.1% 0.1% Wetland -1.4% -0.47% Open Water 4.19% -.002%
Overall Gains & Losses: Cameron County Conversion Type 2001-2006 acreage 2006-2011 acreage Wetland to Upland 1,040.58 2,292.00 Wetland to Open 603.13 165.91 Water Upland to Wetland 56.27 1,345.71 Open Water to 10.45 592.46 Wetland
Overall Gains & Losses: Cameron County 2001-2006 Cameron County Land Change 2006-2011 Cameron County Land Change
Cameron County Wetland Loss 2001-2006: Close Up
Wetland Loss: Cameron County (2006-2011)
Accuracy Assessments Galveston Cameron Year County County 2001 89.89% 87.78% Overall 2006 98.89% 82.22% Accuracy 2011 95.56% 96.67% 2001 0.897 0.875 Kappa 2006 0.989 0.818 2011 0.955 0.960
Summary of Results Wetland loss is greater than wetland gains. Majority of losses were from conversion to upland areas (>80%) In urban areas Galveston County experienced an overall 10% loss between 2001 and 2011 (~5% each study period) Cameron County experienced an overall 2% loss between 2001 and 2011 (1.5% loss 2001-2006 and 0.5% loss 2006-2011) Our maps had above 80% accuracy in identifying between wetland, upland, and open water 20% increase in population for both counties between 2001-2011
Implications of Research Important to see the overall trends in these rapidly changing areas. Can easily compare areas and see priority areas for wetland conservation. Further look at policy and management practices between Galveston and Cameron County. Both had 20% increase in population but had different amount of wetland loss (10% - Galveston County and 2% - Cameron County) Fairly accurate results can be obtained by using a simplified classification system and aerial photography. Cursory knowledge of the area.
References Bao, K 2015. Coastal Wetlands: Coupling Between Ocean and Land Systems. J Coast Res 31.3 : iv. Carle, M. 2011. Estimating Wetland Losses And Gains In Coastal North Carolina: 1994-2001. Wetlands 31.6: 1275-1285. Dahl, TE and Stedman SM. 2013. Status and Trends of wetlands in coastal watersheds of the conterminous United States 2004 to 2009. US Dept of Int, Fisha dn Wildlife Service and NationalOceanic and Atmospheric Administration, National Marine Fisheries Service. (46 p.) Diffenderfer, RP. Accelerated Wetland Losses In Coastal Watersheds. J Am Water Works Assoc. 106.4: 24-26. Galveston Bay Facts [Internet]. n.d. Available from: <http://www.tamug.edu/gbic/gbicresources/bayfacts.html>. Galveston Bay Information Center [Internet]. 2010. Available from: <http://tamug.edu/gbic/about.html>. Martinez ML, Mendoza-Gonzalez G, Silva-Casarin R, Mendoza-Baldwin E. 2014. Land use changes and sea level rise may induce a “coastal squeeze” on the coasts of Veracruz, Mexico. Glob Environ Chang 29:180-188. Moulton, DW, Dahl, TE, Dall, DM. 1997. Texas Coastal Wetlands: Status and Trends, mid-1950s to early 1990s. US Fish and Wildlife Service. South Padre Island, Texas: (TX 78597) Profile: Population, Maps, Real Estate, Averages, Homes, Statistics, Relocation, Travel, Jobs, Hospitals, Schools, Crime, Moving, Houses, News, Sex Offenders [Internet]. n.d. [accessed 02 Feb. 2016]. Available from: <http://www.city-data.com/city/South-Padre-Island-Texas.html>.
Questions & Comments Thank you
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