APCRS-2020-0001
AUTHOR(S):
Wojciech Krawczyk, Piotr Wężyk
TITLE:
MAPPING OF WINDSTORM DAMAGE OCCURRING IN THE FOREST STANDS OF CZERNIEJEWO FOREST DISTRICT (POLISH STATE FORESTS NATIONAL HOLDING) USING AERIAL PHOTOGRAPHS AND SENTINEL-2 SATELLITE IMAGERY
ABSTRACT:
On the night of 11 and 12.08.2017 a severe hurricane passed over Poland, in a belt of almost 300 km, causing damage in forest stands of area exceeding 100 000 ha. The study aimed to demonstrate the implementation of remote sensing technologies in the process of determining the extent of forest stand damages in the Czerniejewo Forest District (RDLP Poznań) caused by wind and monitoring the progress of clean-up work. In this study were used digital aerial orthophotos commissioned by the State Forests National Forest Holding (PGL LP) and Sentinel-2 (ESA) satellite images as well. The area of damaged stands was determined with the use of two approaches, i.e.: supervised classification (approach A) and thresholding of values of Normalised Difference Vegetation Index – NDVI (approach B). The obtained results were compared to reference data obtained by visual interpretation of high resolution RGB aerial orthophotos by RDLP Poznań experts. Monitoring of the progress of the clean-up works in damaged stands was carried out in 9-time intervals. The conducted image classification and spatial GIS analyses showed that the area of stands damaged by the wind was for methods A and B: 579.16 ha and 516.01 ha, respectively, with 631.00 ha as the reference. The results obtained in the study indicate errors in underestimating the area of forest stand damage based on Sentinel-2, i.e.: 51.84 ha (8.2%) in the case of method A and by 114.99 ha (18.2%) for method B. In the whole analysed time, clean-up operations were carried out on the total area of 762.33 ha of damaged forest stands, and their highest intensity was observed in the first 4 months after the storm. The work showed the applicability of free of charge Sentinel-2 (ESA) satellite imagery in the process of determining the extent of forest stand damages, pointing to the supervised classification method (Maximum Likelihood algorithm; ML) as more accurate than using the threshold of NDVI.
KEY WORDS: hurricane, forest stands damage assessment, aerial orthophoto, Sentinel-2 (ESA)
DOI: https://doi.org/10.14681/apcrs.2020.0001