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This data release contains two debris-flow inventories summarizing observations from burned and unburned areas in the western Cascade Range of Oregon (OR). The burned inventory focuses on debris flows that occurred during the first two years after the 2020 Archie Creek, Holiday Farm, Beachie Creek/Lionshead, and Riverside fires (OR_field_observations.csv). The unburned inventory (1995-2022) focuses on debris flows in the same areas (excluding the Riverside Fire). The inventories are derived from field observations (OR_field_observations.csv) and aerial imagery (OR_imagery_observations.csv). They include mapped debris-flow initiation locations, descriptions of the inferred initiation process, other notable site characteristics, and rainfall data. Locations of debris flows observed after wildfires are also linked to USGS postfire debris-flow hazard assessments (USGS, 2022; Staley and others, 2017; Thomas and others 2023). Rainfall characteristics for each debris flow in the inventory are derived from the closest rainfall gage to an observed debris flow (gage_locations.csv). Peak rainfall rates during the known time window of debris-flow initiation are reported for durations of 15 minutes, 30 minutes, 60 minutes, 12 hours, 24 hours, 36 hours, and 48 hours. More detailed explanations of the headers for each of these csv files can be found within the README_csvname.txt file. References: Landslide Hazards Program. (n.d.). Emergency assessment of post-fire debris-flow hazards. U.S. Geological Survey. https://landslides.usgs.gov/hazards/postfire_debrisflow Staley, D. M., Negri, J. A., Kean, J. W., Laber, J. L., Tillery, A. C., and Youberg, A. M., 2017, Prediction of spatially explicit rainfall intensity–duration thresholds for post-fire debris-flow generation in the western United States. Geomorphology, 278, 149–162. https://doi.org/10.1016/j.geomorph.2016.10.019 Thomas, M. A., Kean, J. W., McCoy, S. W., Lindsay, D. N., Kostelnik, J., Cavagnaro, D. B., Rengers, F. K., East, A. E., Schwartz, J. Y., Smith, D. P., and Collins, B. D., 2023, Postfire hydrologic response along the Central California (USA) coast: insights for the emergency assessment of postfire debris-flow hazards. Landslides, 20, 2421-2436. https://doi.org/10.1007/s10346-023-02106-7 

It is widely recognized that nitrogen (N) inputs from watersheds to estuaries are modified during transport through river networks, but changes within tidal freshwater zones (TFZs) have been largely overlooked. This paper sheds new light on the role that TFZs play in modifying the timing and forms of N inputs to estuaries by (1) characterizing spatial and temporal variability of N concentrations and forms in the TFZs of the Mission and Aransas rivers, Texas, USA, and (2) examining seasonal fluxes of N into and out of the Aransas River TFZ. Median concentrations of dissolved inorganic N (DIN) were lower in the TFZs than in upstream non-tidal river reaches and exhibited spatial gradients linked to locations of major N inputs. These spatial patterns were stronger during winter than summer. The forms of N also changed substantially, with DIN changing to organic N (primarily phytoplankton) within the TFZs. Discharge and N flux comparisons for the Aransas River TFZ demonstrated that secular tidal patterns modulate the timing of N export during baseflow conditions: N export far exceeded input during winter, whereas export and input were relatively balanced during summer. While more data are needed to build an annual N budget, our results show that TFZ can change the timing and form of N export immediately upstream of estuaries. 

While organic and inorganic nutrient inputs from land are recognized as a major driver of primary production in estuaries, remarkably little is known about how processes within the tidal freshwater zones (TFZs) of riversmodify these inputs. This study quantifies organic matter (OM) decomposition rates in surface sediment layers in the lower reaches of two south Texas river channels and identifies key parameters that influence sediment decomposition rates. Sediment cores were collected from nontidal and tidal freshwater sites in theMission and Aransas rivers during two summers (June 2015 and June 2016) and two winters (February 2016, January 2017). We measured oxygen consumption rates, organic carbon and nitrogen content, stable isotope ratios (δ13C and δ15N of OM), and sediment porosity. O2 consumption rates in TFZ sediments were 385 ± 88 μmol O2 m−2 h−1 (summer) and 349 ± 87 μmol O2 m−2 h−1 (winter) in the Aransas River and 767 ± 153 μmol O2 m−2 h−1 (summer) and 691 ± 95 μmol O2 m−2 h−1 (winter) in the Mission River. These rates in TFZs were similar to rates in estuaries and higher than rates at non-tidal riverine sites. Rates of sediment O2 consumption were primarily controlled by OM content and temperature. Sediment OM was dominated by algal biomass from in situ production in both TFZs. We hypothesize that algal production and sinking within TFZs is a major pathway for translocation of watershed-derived nutrients from the water column to the sediments within TFZs. Further work is needed to quantify linkages between decomposition, nutrient remineralization, and potential removal through processes such as denitrification. 

The urban heat island (UHI) concept describes heat trapping that elevates urban temperatures relative to rural temperatures, at least in temperate/humid regions. In drylands, urban irrigation can instead produce an urban cool island (UCI) effect. However, the UHI/UCI characterization suffers from uncertainty in choosing representative urban/rural endmembers, an artificial dichotomy between UHIs and UCIs, and lack of consistent terminology for other patterns of thermal variation at nested scales. We use the case of a historically well-enforced urban growth boundary (UGB) around Portland (Oregon, USA): to explore the representativeness of the surface temperature UHI (SUHI) as derived from Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature data, to test common assumptions of characteristically “warm” or “cool” land covers (LCs), and to name other common urban thermal features of interest. We find that the UGB contains heat as well as sprawl, inducing a sharp surface temperature contrast across the urban/rural boundary. The contrast ranges widely depending on the end-members chosen, across a spectrum from positive (SUHI) to negative (SUCI) values. We propose a new, inclusive “urban thermal deviation” (UTD) term to span the spectrum of possible UHI-zero-UCI conditions. We also distinguish at finer scales “microthermal extremes” (MTEs), discrete areas tending in the same thermal direction as their LC or surroundings but to extreme (hot or cold) values, and microthermal anomalies (MTAs), that run counter to thermal expectations or tendencies for their LC or surroundings. The distinction is important because MTEs suggest a need for moderation in the local thermal landscape, whereas MTAs may suggest solutions. 

Abstract Tidal marshes are valuable global carbon sinks, yet large uncertainties in coastal marsh carbon budgets and mediating mechanisms limit our ability to estimate fluxes and predict feedbacks with global change. To improve mechanistic understanding, we assess how net carbon storage is influenced by interactions between crab activity, water movement, and biogeochemistry. We show that crab burrows enhance carbon loss from tidal marsh sediments by physical and chemical feedback processes. Burrows increase near-creek sediment permeability in the summer by an order of magnitude compared to the winter crab dormancy period, promoting carbon-rich fluid exchange between the marsh and creek. Burrows also enhance vertical exchange by increasing the depth of the strongly carbon-oxidizing zone and reducing the capacity for carbon sequestration. Results reveal the mechanism through which crab burrows mediate the movement of carbon through tidal wetlands and highlight the importance of considering burrowing activity when making budget projections across temporal and spatial scales. 

Empirically quantifying tidally-influenced river discharge is typically laborious, expensive, and subject to more uncertainty than estimation of upstream river discharge. The tidal stage-discharge relationship is not monotonic nor necessarily single-valued, so conventional stage-based river rating curves fail in the tidal zone. Herein, we propose an expanded rating curve method incorporating stage-rate-of-change to estimate river discharge under tidal influences across progressive, mixed, and standing waves. This simple and inexpensive method requires (1) stage from a pressure transducer, (2) flow direction from a tilt current meter, and (3) a series of ADP surveys at different flow rates for model calibration. The method was validated using excerpts from 12 tidal USGS gauging stations during baseflow conditions. USGS gauging stations model discharge using a different more complex and expensive method. Comparison of new and previous models resulted in good R2 correlations (min 0.62, mean 0.87 with S.D. 0.10, max 0.97). The method for modeling tidally-influenced discharge during baseflow conditions was applied de novo to eight intertidal stations in the Mission and Aransas Rivers, Texas, USA. In these same rivers, the model was further expanded to identify and estimate tidally-influenced stormflow discharges. The Mission and Aransas examples illustrated the potential scientific and management utility of the applied tidal rating curve method for isolating transient tidal influences and quantifying baseflow and storm discharges to sensitive coastal waters. 

Abstract Tidal freshwater zones (TFZs) are transitional environments between terrestrial and coastal waters. TFZs have freshwater chemistry and tidal physics, and yet are neither river nor estuary based on classic definitions. Such zones have been occasionally discussed in the literature but lack a consistent nomenclature and framework for study. This work proposes a measurable definition for TFZs based on three longitudinal points of interest: (1) the upstream limit of brackish water, (2) the upstream limit of bidirectional tidal velocities, and (3) the upstream limit of tidal stage fluctuations. The resulting size and position of a TFZ is transient and depends on the balance of tidal and riverine forces that evolves over event, tidal, seasonal, and annual (or longer) timescales. The concept, definition, and transient analysis of TFZ position are illustrated using field observations from the Aransas River (Texas, USA) from July 2015 to July 2016. The median Aransas TFZ length was 59.9 km, with a late summer maximum of 66.0 km and a winter minimum of 53.6 km. The TFZ typically (annual median) began 11.8 km upstream from the river mouth (15.4 km winter/11.2 km summer medians) and ended 71.7 km upstream (69.0 km/77.2 km). Seasonally low baseflow in the Aransas River promoted gradual coastal salt encroachment upstream, which shortened the TFZ. However, sporadic large rainfall/runoff events rapidly elongated the TFZ. The TFZ definition establishes a quantifiable framework for analyzing these critical freshwater systems that reside at the nexus of natural and human‐influenced hydrology, tides, and climate.