Victor S. Kuwahara

Dr. Victor S. Kuwahara

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Research Focus & Metrics

Academic Career Length

20Years (2007-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 November 2021 in Environmental Pollution
Verified
Journal Article
Closed access
ECEmily Curren
Emily Curren
VKVictor S. Kuwahara
Victor S. Kuwahara
Teruaki YoshidaTeruaki Yoshida
Teruaki Yoshida
SLSandric Chee Yew Leong
Sandric Chee Yew Leong

24 February 2023 in Water
Verified
Journal Article
Open access
PDF file
GBGetachew Bayable
Getachew Bayable
JCJi Cai
Ji Cai
MMMulatie Mekonnen
Mulatie Mekonnen
SASolomon Addisu
Solomon Addisu
KIKanako Ishikawa
Kanako Ishikawa
VKVictor S. Kuwahara
Victor S. Kuwahara
Lake Tana is Ethiopia’s largest lake and is infested with invasive water hyacinth (E. crassipes), which endangers the lake’s biodiversity and habitat. Using appropriate remote sensing detection methods and determining the seasonal distribution of the weed is important for decision-making, water resource management, and environmental protection. As the demand for the reliable estimation of E. crassipes mapping from satellite data grows, comparing the performance of different machine learning algorithms could help in identifying the most effective method for E. crassipes detection in the lake. Therefore, this study aimed to examine the ability of random forest (RF), support vector machine (SVM), and classification and regression tree (CART) machine learning algorithms to detect E. crassipes and estimating seasonal spatial coverage of the weed on the Google Earth Engine (GEE) platform using Landsat 8 and Sentinel 2 images. Cloud-masked monthly median composite Landsat 8 and Sentinel 2 data from October 2021 and 2022, January 2022 and 2023, March 2022, and June 2022 were used to represent autumn, winter, spring, and summer, respectively. Four spectral indices were derived and used in combination with spectral bands to improve the E. crassipes detection accuracy. All methods achieved greater than 95% and 90% overall accuracy when using Sentinel 2 and Landsat 8 images, respectively. Using both data sets, all methods achieved a greater than 93% F1 score for E. crassipes detection. Though the difference in performance between the methods was small, the RF was the most accurate, while the SVM and CART methods had the same accuracy. The maximum E. crassipes coverage area was observed in autumn (22.4 km2), while the minimum (2.2 km2) was observed in summer. Based on Sentinel 2 data, the E. crassipes area coverage decreased significantly by 62.5% from winter to spring and increased significantly by 81.7% from summer to autumn. The findings suggested that the RF classifier was the most accurate E. crassipes detection algorithm, and autumn was an appropriate season for E. crassipes detection in Lake Tana.

30 June 2008 in Deep Sea Research Part II: Topical Studies in Oceanography
Verified
Journal Article
Closed access
VKVictor S. Kuwahara
Victor S. Kuwahara
FNFrancesco Nencioli
Francesco Nencioli
TDTommy D. Dickey
Tommy D. Dickey
YRYoshimi M. Rii
Yoshimi M. Rii
RBRobert R. Bidigare
Robert R. Bidigare

8 April 2010 in Coral Reefs
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Journal Article
Closed access
PDF file
VKVictor S. Kuwahara
Victor S. Kuwahara
RNR. Nakajima
R. Nakajima
BOB. H. R. Othman
B. H. R. Othman
MKM. R. M. Kushairi
M. R. M. Kushairi
TTT. Toda
T. Toda

1 July 2017 in Estuarine, Coastal and Shelf Science
Verified
Journal Article
Closed access
KTKenji Tsuchiya
Kenji Tsuchiya
VKVictor S. Kuwahara
Victor S. Kuwahara
TYTomoko M. Yoshiki
Tomoko M. Yoshiki
RNRyota Nakajima
Ryota Nakajima
SSShinji Shimode
Shinji Shimode
TTTatsuki Toda
Tatsuki Toda

1 January 2019 in Regional Studies in Marine Science
Verified
Journal Article
Closed access
ECEmily Curren
Emily Curren
Teruaki YoshidaTeruaki Yoshida
Teruaki Yoshida
VKVictor S. Kuwahara
Victor S. Kuwahara
SLSandric Chee Yew Leong
Sandric Chee Yew Leong