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Abstract High tide floods (HTFs) are minor, shallow flooding events whose frequency has increased due to relative sea‐level rise (SLR) and secular changes in tides. Here we isolate and examine the role of historical landscape change (geomorphology, land cover) and SLR on tides and HTF frequency in an urbanized lagoonal estuary: Jamaica Bay, New York. The approach involves data archeology, historical (1870s) map digitization, as well as numerical modeling of the bay. Numerical simulations indicate that a century of landscape alterations (e.g., inlet deepening and widening, channel deepening, and wetland reclamation) increased the mean tidal range at the head of the bay by about 20%. The observed historical shift from the attenuation to amplification of semidiurnal tides is primarily associated with reduced tidal damping at the inlet and increased tidal reflection. The 18% decrease in surface area exerts a minor influence. A 1‐year (2020) water level simulation is used to evaluate the effects of both SLR and altered morphology on the annual number of HTFs. Results show that of 15 “minor flood” events in 2020, only one would have occurred without SLR and two without landscape changes since the 1870s. Spectral and transfer function analyses of water level reveal frequency‐dependent fingerprints of landscape change, with a significant decrease in damping for high‐frequency surges and tides (6–18 hr time scale). By contrast, SLR produced only minor effects on frequency‐dependent amplification. Nonetheless, the geomorphic influence on the dynamical response significantly increases the vulnerability of the system to SLR, particularly high‐tide flooding.
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Compound Minor Floods and the Role of Discharge in the Delaware River Estuary
Abstract Compound floods are often thought of as large, infrequent floods during which extremes of coastal sea level and/or river flow combine with each other or additional factors (e.g., tides and rainfall) to induce major flooding. However, little is known about the potentially compound nature of more frequent, lower‐level floods. Here, we introduce the term “compound minor floods” to define minor floods composed of two or more water‐level sources. We use the Delaware River Estuary as a case study to investigate the prevalence and composition of these minor compound floods along the extent of a tidal river. We apply multiple linear regression to a 22‐year time series of coastal water levels and river discharge to establish the contributions of tides, nontidal open‐ocean effects, and river discharge to minor flood events at eight locations along the tidal Delaware River. We find that most minor flood events are compound in nature, requiring at least two components (e.g., tides and river discharge) to initiate flooding. We identify spatial structure in the relative importance of oceanographic and riverine contributions to minor flooding along the tidal reach of the estuary. These results suggest that incorporating fluvial components into minor flooding assessments is important to fully characterize flood risk along tidal rivers and estuaries.
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- Award ID(s):
- 2123692
- PAR ID:
- 10576013
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 130
- Issue:
- 3
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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