Monitoring the Efficacy of Crested Floatingheart (Nymphoides cristata) Management with Object-Based Image Analysis of UAS Imagery

Adam R Benjamin,Hartwig H Hochmair,Kyle Thayer,Lyn A Gettys,Amr Abd-Elrahman

doi:10.3390/rs13040830

Adam R Benjamin, Hartwig H Hochmair + Show 3 more

Open Access

https://doi.org/10.3390/rs13040830

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Abstract

This study investigates the use of unmanned aerial systems (UAS) mapping for monitoring the efficacy of invasive aquatic vegetation (AV) management on a floating-leaved AV species, Nymphoides cristata (CFH). The study site consists of 48 treatment plots (TPs). Based on six unique flights over two days at three different flight altitudes while using both a multispectral and RGB sensor, accuracy assessment of the final object-based image analysis (OBIA)-derived classified images yielded overall accuracies ranging from 89.6% to 95.4%. The multispectral sensor was significantly more accurate than the RGB sensor at measuring CFH areal coverage within each TP only with the highest multispectral, spatial resolution (2.7 cm/pix at 40 m altitude). When measuring response in the AV community area between the day of treatment and two weeks after treatment, there was no significant difference between the temporal area change from the reference datasets and the area changes derived from either the RGB or multispectral sensor. Thus, water resource managers need to weigh small gains in accuracy from using multispectral sensors against other operational considerations such as the additional processing time due to increased file sizes, higher financial costs for equipment procurements, and longer flight durations in the field when operating multispectral sensors.

Highlights

Aquatic vegetation (AV), known as macrophytes, has important ecological and regulatory functions in lakes, streams, and wetlands [1]
By using a FLAV species (CFH) that is growing in importance due to its relatively recent introduction and rapid growth potential, the analysis presented in this study will benefit water resource managers across Florida and beyond as crested floatingheart (CFH) inevitably spreads to new geographic areas
This study provides a more thorough understanding of unmanned aerial systems (UAS) sensor selection and UAS data acquisition for monitoring the effectiveness of invasive aquatic vegetation management strategies

Summary

Introduction

Aquatic vegetation (AV), known as macrophytes, has important ecological and regulatory functions in lakes, streams, and wetlands [1]. These ecosystem services include habitat provisioning for fauna and waste treatment via nutrient uptake from the water column [2]. Invasive AV can alter native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with native species [3,4]. By monitoring AV, ecosystem changes can be detected. Water resource managers can implement control strategies when and where necessary

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