Data From the Drain: A Sensor Framework That Captures Multiple Drivers of Chronic Coastal Floods

Abstract

Tide gauge water levels are commonly used as a proxy for flood incidence on land. These proxies are useful for projecting how sea‐level rise (SLR) will increase the frequency of coastal flooding. However, tide gauges do not account for land‐based sources of coastal flooding and therefore flood thresholds and the proxies derived from them likely underestimate the current and future frequency of coastal flooding. Here we present a new sensor framework for measuring the incidence of coastal floods that captures both subterranean and land‐based contributions to flooding. The low‐cost, open‐source sensor framework consists of a storm drain water level sensor, roadway camera, and wireless gateway that transmit data in real‐time. During 5 months of deployment in the Town of Beaufort, North Carolina, 24 flood events were recorded. Twenty‐five percent of those events were driven by land‐based sources—rainfall, combined with moderate high tides and reduced capacity in storm drains. Consequently, we find that flood frequency is higher than that suggested by proxies that rely exclusively on tide gauge water levels for determining flood incidence. This finding likely extends to other locations where stormwater networks are at a reduced drainage capacity due to SLR. Our results highlight the benefits of instrumenting stormwater networks directly to capture multiple drivers of coastal flooding. More accurate estimates of the frequency and drivers of floods in low‐lying coastal communities can enable the development of more effective long‐term adaptation strategies.

The Global Drivers of Chronic Coastal Flood Hazards Under Sea‐Level Rise

“…This has subsequently been found to apply for Pacific Islands more generally (Dusek et al., 2022). The derived thresholds were also found to be too high to capture many observed flood events occuring via storm‐drain backflow mechanisms in Beaufort, North Carolina, even though storm drain water levels were well‐correlated to tide gauge observations (Gold et al., 2023).…”

“…Furthermore, several locations on the US Southeast Atlantic, and eastern Australia (Bureau of Meteorology, 2022) have offsets of just 0.15 m between one or more flood levels. This highlights the need for the development of global flood impact databases such as those that already exist for Europe (Ciavola et al., 2018; Haigh et al., 2017) and systematic collection of impact‐based thresholds defined in national and local coastal flood studies (e.g., Ezer, 2022; Gold et al., 2023; Hague et al., 2022; Smith & Juria, 2019; Thompson et al., 2019). Further investment in LiDAR surveys will also improve the coverage of DEMs with small enough vertical errors to distinguish between floods of different severities.…”

“…To study coastal flood hazards, one must ascertain the water levels that pose a threat over the timescale and region of interest (Rasmussen et al., 2022; WMO, 2015). To do this, many studies define coastal flood thresholds that represent the minimum sea level associated with some specified impact (Gold et al., 2023; Hague et al., 2019; Moore & Obradovich, 2020). These can be defined by relevant government agencies (Burgos et al., 2018; Dahl et al., 2017; Karegar et al., 2017; Sweet et al., 2014; Sweet & Park, 2014), or by leveraging social or news media and local monitoring programs (Ezer, 2022; Gold et al., 2023; Hague et al., 2022, 2020, 2019; Hino et al., 2019; Moore & Obradovich, 2020; Ritman et al., 2022; Thompson et al., 2019).…”

“…To do this, many studies define coastal flood thresholds that represent the minimum sea level associated with some specified impact (Gold et al., 2023; Hague et al., 2019; Moore & Obradovich, 2020). These can be defined by relevant government agencies (Burgos et al., 2018; Dahl et al., 2017; Karegar et al., 2017; Sweet et al., 2014; Sweet & Park, 2014), or by leveraging social or news media and local monitoring programs (Ezer, 2022; Gold et al., 2023; Hague et al., 2022, 2020, 2019; Hino et al., 2019; Moore & Obradovich, 2020; Ritman et al., 2022; Thompson et al., 2019). Unfortunately, such thresholds have only been systematically defined in the United States (US) and Australia, limiting their utility for global studies.…”

“…Chronic flooding is defined quantitatively based on the frequency, rather than the severity, of impacts. Definitions vary between studies but 50 days per year is sufficient for flooding to be considered chronic under all published definitions, and is used subsequently (Buchanan et al., 2019; Gold et al., 2023; Sweet & Park, 2014; Thompson et al., 2019). Minor flooding requires the least SLR to reach chronic frequencies and has been the primary focus of most chronic flood studies to date.…”