Search for: All records

Abstract Decreases in shallow-water habitat area (SWHA) in the Lower Columbia River and Estuary (LCRE) have adversely affected salmonid populations. We investigate the causes by hindcasting SWHA from 1928 to 2004, system-wide, based on daily higher high water (HHW) and system hypsometry. Physics-based regression models are used to represent HHW along the system as a function of river inflow, tides, and coastal processes, and hypsometry is used to estimate the associated SWHA. Scenario modeling is employed to attribute SWHA losses to levees, flow regulation, diversion, navigational development, and climate-induced hydrologic change, for subsidence scenarios of up to 2 m, and for 0.5 m fill. For zero subsidence, the system-wide annual-average loss of SWHA is 55 ± 5%, or 51 × 10⁵ ha/year; levees have caused the largest decrease ($${54}_{-14}^{+5}$$ ${54}_{-14}^{+5}$%, or ~ 50 × 10⁵ ha/year). The loss in SWHA due to operation of the hydropower system is small, but spatially and seasonally variable. During the spring freshet critical to juvenile salmonids, the total SWHA loss was$${63}_{-3}^{+2}$$ ${63}_{-3}^{+2}$%, with the hydropower system causing losses of 5–16% (depending on subsidence). Climate change and navigation have caused SWHA losses of$${5}_{-5}^{+16}$$ $5_{-5}^{+16}$% and$${4}_{-6}^{+14}$$ $4_{-6}^{+14}$%, respectively, but with high spatial variability; irrigation impacts have been small. Uncertain subsidence causes most of the uncertainty in estimates; the sum of the individual factors exceeds the total loss, because factors interact. Any factor that reduces mean or peak flows (reservoirs, diversion, and climate change) or alters tides and along-channel slope (navigation) becomes more impactful as assumed historical elevations are increased to account for subsidence, while levees matter less. 

Abstract. Using archival research methods, we recovered and combined data from multiple sources to produce a unique, 140-year record of daily watertemperature (Tw) in the lower Willamette River, Oregon (1881–1890, 1941–present). Additional daily weather and river flow records from the 1850s onwards are used to develop and validate a statistical regression model of Tw for 1850–2020. The model simulates the time-lagged response of Tw to air temperature and river flow and is calibrated for three distinct time periods: the late 19th, mid-20th, and early 21st centuries. Results show that Tw has trended upwards at 1.1 ∘C per century since the mid-19th century, with the largest shift in January and February (1.3 ∘C per century) and the smallest in May and June (∼ 0.8 ∘C per century). The duration that the river exceeds the ecologically important threshold of 20 ∘C has increased by about 20 d since the 1800s, to about 60 d yr−1. Moreover, cold-water days below 2 ∘C have virtually disappeared, and the river no longer freezes. Since 1900, changes are primarily correlated with increasesin air temperature (Tw increase of 0.81 ± 0.25 ∘C) but also occur due to alterations in the river system such as depth increases from reservoirs (0.34 ± 0.12 ∘C). Managed release of water affects Tw seasonally, with an average reduction of up to 0.56 ∘C estimated for September. River system changes have decreased variability (σ) in daily minimum Tw by 0.44 ∘C, increased thermal memory, reduced interannual variability, and reduced the response to short-term meteorological forcing (e.g., heat waves). These changes fundamentally alter the response of Tw to climate change, posing additional stressors on fauna. 

Abstract. The eruption of the Hunga Tonga-Hunga Ha'apai volcano on 15 January 2022 provided a rare opportunity to understand global tsunamiimpacts of explosive volcanism and to evaluate future hazards, includingdangers from “volcanic meteotsunamis” (VMTs) induced by the atmosphericshock waves that followed the eruption. The propagation of the volcanic andmarine tsunamis was analyzed using globally distributed 1 min measurementsof air pressure and water level (WL) (from both tide gauges and deep-waterbuoys). The marine tsunami propagated primarily throughout the Pacific,reaching nearly 2 m at some locations, though most Pacific locationsrecorded maximums lower than 1 m. However, the VMT resulting from theatmospheric shock wave arrived before the marine tsunami and propagatedglobally, producing water level perturbations in the Indian Ocean, theMediterranean, and the Caribbean. The resulting water level response of manyPacific Rim gauges was amplified, likely related to wave interaction withbathymetry. The meteotsunami repeatedly boosted tsunami wave energy as itcircled the planet several times. In some locations, the VMT was amplifiedby as much as 35-fold relative to the inverse barometer due to near-Proudmanresonance and topographic effects. Thus, a meteotsunami from a largereruption (such as the Krakatoa eruption of 1883) could yield atmosphericpressure changes of 10 to 30 mb, yielding a 3–10 m near-field tsunami thatwould occur in advance of (usually) larger marine tsunami waves, posingadditional hazards to local populations. Present tsunami warning systems donot consider this threat. 

Abstract. We investigate here the effects of geometric properties (channel depth andcross-sectional convergence length), storm surge characteristics, friction,and river flow on the spatial and temporal variability of compound floodingalong an idealized, meso-tidal coastal-plain estuary. An analytical model isdeveloped that includes exponentially convergent geometry, tidal forcing,constant river flow, and a representation of storm surge as a combination oftwo sinusoidal waves. Nonlinear bed friction is treated using Chebyshevpolynomials and trigonometric functions, and a multi-segment approach isused to increase accuracy. Model results show that river discharge increasesthe damping of surge amplitudes in an estuary, while increasing channeldepth has the opposite effect. Sensitivity studies indicate that the impactof river flow on peak water level decreases as channel depth increases,while the influence of tide and surge increases in the landward portion ofan estuary. Moreover, model results show less surge damping in deeperconfigurations and even amplification in some cases, while increasedconvergence length scale increases damping of surge waves with periods of 12–72 h. For every modeled scenario, there is a point where river dischargeeffects on water level outweigh tide/surge effects. As a channel isdeepened, this cross-over point moves progressively upstream. Thus, channeldeepening may alter flood risk spatially along an estuary and reduce thelength of a river estuary, within which fluvial flooding is dominant. 

Nuisance flooding (NF) is defined as minor, nondestructive flooding that causes substantial, accumulating socioeconomic impacts to coastal communities. While sea-level rise is the main driver for the observed increase in NF events in the United States, we show here that secular changes in tides also contribute. An analysis of 40 tidal gauge records from U.S. coasts finds that, at 18 locations, NF increased due to tidal amplification, while decreases in tidal range suppressed NF at 11 locations. Estuaries show the largest changes in NF attributable to tide changes, and these can often be traced to anthropogenic alterations. Limited long-term measurements from estuaries suggest that the effects of evolving tides are more widespread than the locations considered here. The total number of NF days caused by tidal changes has increased at an exponential rate since 1950, adding ~27% to the total number of NF events observed in 2019 across locations with tidal amplification.