the need for hand-engineering the features [5]. In addition to the classification-based approach, a
few studies use the segmentation results to categorize the image as flooded or non-flooded. In this
approach, the images acquired from UAV are segmented and assigned a semantic label (flooded/non-
flooded) to each pixel in the image [2] [3] [6]. For instance, authors in [2] used Fully Convolutional
Networks (FCN) to segment the UAV images and detect the flooded regions. In separate work, in
addition to segmenting the optical UAV images, the digital elevation model was analysed to detect
the flooded region [3]. In another study, an unsupervised segmentation algorithm was utilized to
identify the flooded regions [6]. However, most existing classification and segmentation methods
for identifying the flooded regions are limited to a particular region. While [2, 3] analysed images
of flood-prone areas of North Carolina, USA, [6] analysed images acquired in Texas, USA, after
Hurricane Harvey. Extending these methods to new regions such as flood-prone regions of South Asia
would require manually annotating additional images, which is a time-consuming process. There is a
need to develop methods for detecting flooded regions that can be generalized to unseen regions with
minimum manual intervention.
The work proposes two texture features-based approaches to classify UAV aerial images as flooded or
non-flooded across different geographical regions. Indeed, the texture features of pixels corresponding
to water are different from that of other classes (Road, Buildings, greenery, etc), and, therefore can
be used to identify flooded regions. In the first approach, an artificial neural network (ANN) is
proposed in this work which distinguishes the images in texture feature space. In another approach,
a texture feature-based unsupervised segmentation is proposed to first segment the images. The
number of pixels corresponding to the flooded region is then used to classify the image as flooded
or non-flooded. The segmentation-based approach is an extension of the method proposed in [6].
A texture-based unsupervised segmentation method was proposed in [6] to assess the severity of
flooding in UAV aerial images of the same geographical region. In this work, we adapt this method to
ensure cross-geography generalization. The proposed method can be utilized to identify the flooded
region and assess the flood severity in a UAV aerial image of any region. In this work, the two
proposed methods are compared with other existing machine learning classifiers and segmentation
methods (UNet [9]) to assess the performance of the proposed methods in detecting flooded regions
across different regions.
2 Methodology
This work extends the texture-based unsupervised segmentation approach proposed in [6] for flooded
region identification for cross-geography generalization. A summary of this unsupervised segmenta-
tion approach is presented in Section 2.1. In addition, this work proposes a neural network-based
approach to identify flooded regions (Section 2.2 ).
2.1 Texture Based Unsupervised Segmentation
The input image is first segmented into different regions using k-means segmentation. The segmen-
tation is based on color (LAB color space) and texture information (Local Binary Pattern (LBP)).
Including texture features ensure a more robust identification of regions covered with water. Indeed,
pixels representing water have a distinctive texture appearance compared to other regions (roads,
buildings, etc). The segmented region does not indicate which of the
k
regions represent the flooded
area. Therefore, each
k
regions are compared with a reference flooded region using the histogram of
Local Binary Pattern features. Subsequently, the input image is categorized as flooded or non-flooded
based on the number of pixels corresponding to the flooded region. In [6], the reference flooded
the region and the input image were acquired in the same region. However, this work utilizes the
reference flooded image of a completely different region. The use of the unsupervised segmentation
approach along with reference images of a different region ensures that the proposed approach can be
adapted to identify the flooded area of any region with minimum user supervision.
2.2 Artificial Neural Network
A customized Neural Network is proposed in this work for identifying the flooded regions in UAV
aerial images. The input to the neural network is Local Binary Pattern (LBP) computed on the input
image. Using LBP features instead of gray-scale or color intensities ensures that the network learns
the texture pattern of the input image. The network consists of a sequence of seven dense layers
2