Measuring Inundation Depth in a Subway Station Using the Laser Image Analysis Method

Abstract

Subway station platforms are vulnerable to flood damage. Thus, investigation of inundation properties in subway platforms is required to ensure the safety of citizens against flooding. In this study, the evacuation time and safety were analyzed in a subway station model using inundation depth measurements. The subway station model contained shallow water depth conditions, which did not allow for contact-type measurement devices. Instead, an image analysis procedure using laser images was proposed to measure the inundation depth. The proposed laser image analysis method can recognize a boundary line between the water and air by visualizing the water surface using a laser sheet. The inundation depth measurements using the image analysis method were reasonably accurate, resulting in differences of 2.97–7.67% compared to the results obtained using a digital point gauge. When inflow positions and flowrates of rainwater were changed, the measured results showed that the inundation depth increased in areas in which the rainwater inflow was relatively small or collided when moving in the direction opposite to the rainwater. The calculated evacuation time from the subway station showed that a drainage system is required to decrease the inundation depth in areas of inflowing rainwater collision. Furthermore, the estimated results of evacuation safety showed that safety handles are necessary even in low depth regions to prevent people from falling down due to increased flow velocity, during evacuation.

Stochastic Modeling for Estimating Real-Time Inundation Depths at Roadside IoT Sensors Using the ANN-Derived Model

“…Recently, with the establishment of the dike system, flooding is triggered merely as a result of overtopping from the embankments; in contrast, inundation frequently occurs in the urban and drainage zone owing to the failure of draining the runoff through the sewer systems [1]. In the past, the flood early warning operation was executed based on specific thresholds (e.g., rainfall or inundation depth) in accordance with real-time measurements; however, the real-time practical inundation depths, especially in urban areas, are hardly measured owing to the limitation of measurement equipment or hindrance in data acquisition, processing, and analysis [1][2][3].…”

Stochastic modeling of gridded short-term rainstorms

“…For example, the results from numerical simulation show that the inundation depths at the locations and corresponding flooding areas are important and advantageous in relation to the hydrological/hydraulic analyses regarding the quantification and evaluation of the flood-induced damage (Smith 1997). However, it remains generally difficult to measure the real-time practical inundation-depth hydrograph and even the induced flooding area due to the limitation of measurement equipment or hindrance in data acquisition, processing, and analysis (e.g., Amarnath 2014;Park et al 2018); this situation possibly leads to a lack of reliable references regarding the fine spatiotemporal resolution required for the parameter calibration of the hydraulic numerical models (Shen et al 2019). Despite the fact that the possible maximum flooding area caused by a rainstorm event can be estimated in accordance with the observed maximum inundation-depth recorded at particular locations used to calibrate the parameters of a hydraulic numerical simulation model, the resulting temporal and spatial hydrological features (e.g., inundation depth) include uncertainties with high likelihood attributed to insufficient long-term observations (Hardesty et al 2018).…”

A Sensing and Monitoring System for Hydrodynamic Flow Based on Imaging and Ultrasound

“…Moreover it is also possible to use ultrasonic sensors to develop an effective monitoring system and to ensure adequate transmission rates and to prevent data loss [15,16,17,18]. Level measurement of the river/channel by ultrasound remains one the most important techniques because it is independent from temperature.…”