water Article A Deterministic Topographic Wetland Index Based on LiDAR-Derived DEM for Delineating Open-Water Wetlands Linlong Bian 1, *, Assefa M. Melesse 2 , Arturo S. Leon 1 , Vivek Verma 1 and Zeda Yin 1   Citation: Bian, L.; Melesse, A.M.; Leon, A.S.; Verma, V.; Yin, Z. A Deterministic Topographic Wetland Index Based on LiDAR-Derived DEM for Delineating Open-Water Wetlands. Water 2021, 13, 2487. https:// doi.org/10.3390/w13182487 Academic Editor: Thomas Meixner Received: 12 August 2021 Accepted: 7 September 2021 Published: 10 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Civil and Environmental Engineering, Florida International University, Miami, FL 33199, USA; arleon@fiu.edu (A.S.L.); vverm002@fiu.edu (V.V.); zyin005@fiu.edu (Z.Y.) 2 Department of Earth and Environment, Florida International University, Miami, FL 33199, USA; melessea@fiu.edu * Correspondence: lbian003@fiu.edu; Tel.: +1-305-674-6754 Abstract: Wetlands play a significant role in flood mitigation. Remote sensing technologies as an efficient and accurate approach have been widely applied to delineate wetlands. Supervised classifi- cation is conventionally applied for remote sensing technologies to improve the wetland delineation accuracy. However, performing supervised classification requires preparing the training data, which is also considered time-consuming and prone to human mistakes. This paper presents a deterministic topographic wetland index to delineate wetland inundation areas without performing supervised classification. The classic methods such as Normalized Difference Vegetation Index, Normalized Difference Water Index, and Topographic Wetness Index were chosen to compare with the proposed deterministic topographic method on wetland delineation accuracy. The ground truth sample points validated by Google satellite imageries from four different years were used for the assessment of the delineation overall accuracy. The results show that the proposed deterministic topographic wetland index has the highest overall accuracy (98.90%) and Kappa coefficient (0.641) among the selected approaches in this study. The findings of this paper will provide an alternative approach for delineating wetlands rapidly by using solely the LiDAR-derived Digital Elevation Model. Keywords: wetland delineation; supervised classification; LiDAR-derived DEM; deterministic topo- graphic approach; TWI; NDVI; NDWI 1. Introduction It has been well-documented that wetlands are significantly effective in alleviating floods [1,2]. They can perform as a water storage unit to detain part of peak runoff during a rainfall event. For example, it is estimated that the 8500 acres of wetlands along the Charles River in Massachusetts used for natural flood storage have a present value for flood prevention of $33,370 per acre [3]. Another study indicated that only 13 million acres of wetlands (3% of the upper Mississippi watershed) would have been required in the upper Mississippi watershed to avoid a devastating flood in 1993 [4]. A study conducted by Nivitzki [5] concluded that a watershed with as little as 5% lake and wetland area might lead to a 40–60% lower flood peak. The research conducted by Leon et al. [6] and Tang et al. [7,8] indicated that by dynamically releasing water from upland wetlands, 3.5% of the hypothetical wetland areas in the Cypress Creek watershed located in the northwest of Houston TX could significantly eliminate the flooded area by around 75%. Since wetlands perform a vital function to detain runoff, it is necessary and critical to comprehensively understand the spatial distribution, the inundation area, and the maximum storage capacity of the wetlands in a watershed for the flood mitigation study. From the perspective of identifying the location and delineating the inundation extent for wetlands, the ground-based survey is considered the most accurate method. How- ever, aside from the need for specific experts on-site, the traditional method can be time- consuming and costly as it involves detailed on-site surveys such as extraction of soil Water 2021, 13, 2487. https://doi.org/10.3390/w13182487 https://www.mdpi.com/journal/water