A Remote Sensing Based Integrated Approach to Quantify the Impact of Fluvial and Pluvial Flooding in an Urban Catchment

Abstract

Pluvial (surface water) flooding is often the cause of significant flood damage in urbanareas. However, pluvial flooding is often overlooked in catchments which are historically knownfor fluvial floods. In this study, we present a conceptual remote sensing based integrated approachto enhance current practice in the estimation of flood extent and damage and characterise the spatialdistribution of pluvial and fluvial flooding. Cockermouth, a town which is highly prone to flooding,was selected as a study site. The flood event caused by named storm Desmond in 2015 (5-6/12/2015)was selected for this study. A high resolution digital elevation model (DEM) was produced from acomposite digital surface model (DSM) and a digital terrain model (DTM) obtained from theEnvironment Agency. Using this DEM, a 2D flood model was developed in HEC-RAS (v5) 2D forthe study site. Simulations were carried out with and without pluvial flooding. Calibrated modelswere then used to compare the fluvial and combined (pluvial and fluvial) flood damage areas fordifferent land use types. The number of residential properties affected by both fluvial and combinedflooding was compared using a combination of modelled results and data collected from UnmannedAircraft Systems (UAS). As far as the authors are aware, this is the first time that remote sensingdata, hydrological modelling and flood damage data at a property level have been combined todifferentiate between the extent of flooding and damage caused by fluvial and pluvial flooding inthe same event. Results show that the contribution of pluvial flooding should not be ignored, evenin a catchment where fluvial flooding is the major cause of the flood damages. Although theadditional flood depths caused by the pluvial contribution were lower than the fluvial flood depths,the affected area is still significant. Pluvial flooding increased the overall number of affectedproperties by 25%. In addition, it increased the flood depths in a number of properties that wereidentified as being affected by fluvial flooding, in some cases by more than 50%. These findingsshow the importance of taking pluvial flooding into consideration in flood management practices.Further, most of the data used in this study was obtained via remote sensing methods, includingUAS. This demonstrates the merit of developing a remote sensing based framework to enhancecurrent practices in the estimation of both flood extent and damage.

Using High-Density LiDAR Data and 2D Streamflow Hydraulic Modeling to Improve Urban Flood Hazard Maps: A HEC-RAS Multi-Scenario Approach

“…Earth Observation (EO) datasets (e.g., space borne, aerial images, and satellite images) together with geographic information systems (GIS) can be used to determine the extent of flood areas and for the production of flood hazard and risk maps [43]. Combined with the use of remote sensing (RS) and GIS, EO datasets provide a favorable environment for relevant information processing in order to obtain the spatial extent of flood hazard areas and flood mapping [44][45][46][47]. Even if the benefits are high, this technique offers valuable information only for specific flood events, and this aspect is perceived as a disadvantage because future flood details and impact cannot be investigated [42,45].…”

“…where, h is the water depth (m), p and q are the specific flow in the x and y directions (m 2 s −1 ), ζ is the surface elevation (m), g is the acceleration due to gravity (ms −2 ), n is the Manning's Roughness coefficient (m −1/3 s), ρ is the water density (kg m −3 ), τ xx , τ yy , and τ xy are the components of the effective shear stress and f is the Coriolis (s −1 ). When the diffusive wave is selected, the inertial terms of the momentum equations are neglected: ∂p/∂t + ∂/∂x p 2 /h + ∂/∂y (pq/h) = 0 (Equation (2)); ∂q/∂t + ∂/∂y q 2 /h + ∂/∂x (pq/h) = 0 (Equation (3)) [42,45,71]. Due to their faster computational time and greater stability properties, the 2D diffusion wave equations were preferred in the present study [70].…”

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

“…UAS-based photography has been extensively used to acquire data in inaccessible locations and create high resolution DEMs, map flood-prone areas and to enhance hydraulic modeling [93][94][95][96][97]. In particular, Sf M techniques have seen a strong development as an alternative approach to classical digital photogrammetry in the study of floods, leading to an increasing body of literature in the last years; Özcan and Özcan [98] extracted a highresolution DEM of a flood-vulnerable river in Turkey applying UAS-based SfM.…”

Guidelines for the Use of Unmanned Aerial Systems in Flood Emergency Response

“…A set of floating wireless sensors are deployed within the flood extent by multiple UAS to capture water velocity readings at multiple locations [50]. Flood source identification (fluvial, pluvial, groundwater) Sources of flooding can be identified based on damaged caused within/outside the fluvial flood extent [15,57] or based on differences in water temperature [58].…”