Mapping of Hurricane Harvey-induced Tree Blow-downs in a Coastal Floodplain Forest

Authors: Anthony Filippi*, Texas A&M University, Inci Guneralp, Texas A&M University, Andong Ma, Texas A&M University, Cesar Castillo, Texas A&M University, Mengqu Han, Texas A&M University, Joseph Wade, Texas A&M University, Haoyan Chen, Texas A&M University, Billy Hales, Texas A&M University, Dongshuo Lu, Texas A&M University, Nicole Hernandez, Texas A&M University, Christy Attaway, Texas A&M University
Topics: Hazards, Risks, and Disasters, Remote Sensing, Biogeography
Keywords: Floodplain forests, coastal zone, blown-down trees, mapping, delineation
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Hurricane Harvey passed directly over the Mission River on the Coastal Bend of Texas, where its rainfall produced moderate flooding of the river, and the high-speed winds yielded significant instances of blown-down trees within the Mission River floodplain forest. Blown-down trees can affect flood-inundation patterns within a river-floodplain system. Accurately mapping blown-down trees in floodplain-forests over broad areal extents constitutes a critical stage in better understanding river-floodplain system dynamics. However, such mapping can be difficult in areas with complex, heterogeneous forest canopies of varying degrees of canopy closure that can occlude fallen trees. The objective of this study is to determine the number and distribution of hurricane-induced blown-down trees within a deciduous/broadleaf coastal floodplain forest using manual/visual image interpretation-based delineation. The selected study area is located within the Mission-Aransas National Estuarine Research Reserve (MANERR), which is in the Coastal Bend region of Texas, USA. High-spatial resolution aerial photographs and satellite images, acquired pre- and post-hurricane during leaf-off conditions, were subjected to visual image interpretation, and fallen trees were manually digitized. Manually-digitized fallen-tree polygons were compared with field surveys to quantitatively assess image-derived polygon accuracy. Results indicate that Hurricane Harvey yielded a large number of tree blowdowns over the approximately 40-square-kilometer study area, and that manual image interpretation of high-spatial resolution remote-sensing images can provide useful tree-blowdown counts. However, fallen trees are under-counted in areas with marked canopy closure. These results are useful for hydrodynamic modeling and floodplain system management, as well as assessment of plant and animal habitats.

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