Tidal Delaware River Research Articles

Sea Level Rise-Induced Transition from Rare Fluvial Extremes to Chronic and Compound Floods

Flooding is becoming more frequent along U.S. coastlines due to the rising impacts of fluvial and coastal flood sources, as well as their compound effects. However, we have a limited understanding of mechanisms whereby sea level rise (SLR) changes flood drivers and contributes to flood compounding. Additionally, flood mitigation studies for fluvial floodplains near tidal water bodies often overlook the potential future contribution of coastal water levels. This study investigates the role of SLR in inducing high-tide flooding (HTF) and compound flooding in a neighborhood that lies on a fluvial floodplain. Eastwick, Philadelphia, is a flood-prone neighborhood that lies on the confluence of two flashy, small tributaries of the tidal Delaware River. We develop a combined 1D-2D HEC-RAS fluvial-coastal flood model and demonstrate the model’s accuracy for low-discharge tidal conditions and the extreme discharge conditions of tropical Cyclone (TC) Isaias (2020) (e.g., Root Mean Square Error 0.08 and 0.13 m, respectively). Simulations show that Eastwick may experience SLR-induced HTF as soon as the 2060s, and the flood extent (34.4%) could become as bad as present-day extreme event flooding (30.7% during TC Isaias) as soon as the 2080s (based on 95th percentile SLR projections). Simulations of Isaias flooding with SLR also indicate a trend toward compounding of extreme fluvial flooding. In both cases the coastal flood water enters Eastwick through a different pathway, over a land area not presently included in some fluvial flood models. Our results show that SLR will become an important contributor to future flooding even in fluvial floodplains near tidal water bodies and may require development of compound flood models that can capture new flood pathways.

First Observations of Movements of Invasive Flathead Catfish (Pylodictis olivaris) in the Tidal Delaware River Based on Acoustic Telemetry

Pylodictis olivaris (Flathead Catfish) is a large piscivorous ictalurid catfish that has been introduced widely outside of its native range. Introduced Flathead Catfish are recognized as invasive in many locations and have contributed to declines in native fishes. Flathead Catfish were first documented in the mainstem Delaware River in 2001 and now occupy at least 200 km of tidal and non-tidal habitats. This paper describes the movements of 2 Flathead Catfish opportunistically tagged with acoustic transmitters in the tidal Delaware River. The first Flathead Catfish, tagged in November 2005 and tracked for 1055 days, occupied a 26-km reach of the upper tidal river and evidenced 3 cycles of seasonal movement between the same areas of the river. The second Flathead Catfish, tagged in January 2020 and tracked for 340 days, occupied a 49-km reach of the lower tidal Delaware River and was detected for an extended period in the lower Christina River. This catfish also demonstrated seasonal downriver and upriver movements, but exhibited weaker site fidelity than the other individual. Both Flathead Catfish tended to move at night or in the morning, which is typical for the species, although daylight movements were also observed. The annual ranges of river occupied by the Flathead Catfish in this study were larger than previously described for introduced populations, and suggest that any program of management or control would have to be at a watershed scale. This study is the first to describe seasonal movements of Flathead Catfish in the Delaware River, documents a 17-km downriver expansion of the species' range, and provides the first record of Flathead Catfish in the Christina River.

Skill of ensemble flood inundation forecasts at short- to medium-range timescales

We investigate the ability to improve flood inundation forecasts at short- to medium-range (1–7 days) timescales through weather ensembles and statistical water surface elevation (WSE) postprocessing. To generate the flood inundation forecasts, a one-dimensional hydraulic model, namely the Hydrologic Engineering Center’s River Analysis System (HEC-RAS), is coupled to a regional hydrological ensemble prediction system (RHEPS). The RHEPS is comprised of: i) hydrometeorological observations; ii) weather ensembles from the National Centers for Environmental Prediction Global Ensemble Forecast System Reforecast version 2 (GEFSRv2); and iii) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM) as the hydrological model. The coupled RHEPS-hydraulic system is evaluated along the tidal Delaware River near the City of Philadelphia, Pennsylvania, U.S. For the evaluation, emphasis is placed on the tidal-riverine transitional zone of the Delaware River and the downstream propagation of hydrometeorological uncertainty through the flood inundation forecasts. The coupled system is used to generate hourly flood inundation forecasts at lead times from 1 to 7 days, over the period 2008–2013. Additionally, WSEs from the coupled system are statistically postprocessed using quantile regression (QR). Results show that the raw flood inundation ensemble forecasts exhibit higher skill than the deterministic ones. We also find that statistical postprocessing improves the skill of the raw flood inundation ensemble forecasts, with greater improvements at the longer lead times (>3 days). Overall, we find that both weather ensembles and statistical WSE postprocessing can be used to enhance the skill of flood inundation forecasts at short- to medium-range timescales. In turn, this may serve to enhance the spatial representation of flood forecasts several days in advance, which could contribute in the future to making flood forecast communication and warnings more effective.

Monitoring the tidal Delaware River for ambient toxicity

This study assessed ambient waters in an urbanized area of the Delaware River, to determine whether river water samples exhibited chronic lethal or sublethal toxicity when measured in laboratory experiments. Toxicity was assessed at 16 fixed stations in the main-stem river and 29 stations in tributaries of the tidal Delaware River with salinities from 0 to 15 parts per 1000 (ppt) using Pimephales promelas, Americamysis bahia, Menidia beryllina, and Ceriodaphnia dubia in 7-d tests; Pseudokirchneriella subcapitata in a 96-h test; and Hyalella azteca in a 10-d water-only test. The toxicity tests measured organism survival, growth, and reproduction. Results from testing water samples collected in 4 different y indicated that the samples from sites tested in the main-stem of the Delaware River and from the majority of its tributaries did not produce chronic toxicity. The surveys identified tributaries that warrant further assessment for toxicity.

Water quality trends in the Delaware River Basin (USA) from 1980 to 2005

In 1940, the tidal Delaware River was "one of the most grossly polluted areas in the United States." During the 1950s, water quality was so poor along the river at Philadelphia that zero oxygen levels prevented migration of American shad leading to near extirpation of the species. Since then, water quality in the Delaware Basin has improved with implementation of the 1961 Delaware River Basin Compact and 1970s Federal Clean Water Act Amendments. At 15 gages along the Delaware River and major tributaries between 1980 and 2005, water quality for dissolved oxygen, phosphorus, nitrogen, and sediment improved at 39%, remained constant at 51%, and degraded at 10% of the stations. Since 1980, improved water-quality stations outnumbered degraded stations by a 4 to 1 margin. Water quality remains good in the nontidal river above Trenton and, while improved, remains fair to poor for phosphorus and nitrogen in the tidal estuary near Philadelphia and in the Lehigh and Schuylkill tributaries. Water quality is good in heavily forested watersheds (>50%) and poor in highly cultivated watersheds. Water quality recovery in the Delaware Basin is coincident with implementation of environmental laws enacted in the 1960s and 1970s and is congruent with return of striped bass, shad, blue crab, and bald eagle populations.

Experiments with Broadband Sonar for the Detection and Identification of Endangered Shortnose Sturgeon

AbstractExperiments were conducted in the tidal Delaware River to evaluate the use of broadband sonar to remotely detect and identify shortnose sturgeon, a federally listed endangered species. The objectives of this study were to determine if shortnose sturgeon could be detected by broadband sonar and, if so, to develop classifiers that could differentiate shortnose sturgeon from co-occurring fish species. Broadband acoustic echoes were collected from shortnose sturgeon, three non-sturgeon fish species, and the river bottom. Classifiers were developed using neural network analysis of the normalized frequency response spectra from each target class. Two independent classifiers were developed, one that distinguished “sturgeon” from the river “bottom” and a second that classified targets as “sturgeon,” “non-sturgeon fish,” and the “bottom.” The training performance of the classifiers was 100% for each class. Testing of the two-class sturgeon vs. the bottom classifier resulted in correct classification of 96.6% of the shortnose sturgeon detections and incorrect classification of 3.4% of actual sturgeon echoes as bottom. None of the bottom detections were misclassified as sturgeon. Testing of the three-class classifier resulted in the correct classification of 89.0% of the actual sturgeon detections, and incorrect classification of 8.5% of actual sturgeon detections as non-sturgeon fish and 2.5% of actual sturgeon detections as bottom. Some 27.1% of the actual non-sturgeon fish echoes and 5.9% of actual bottom echoes were incorrectly identified as sturgeon, yielding a false-positive rate of 16.5%. Given that the “non-sturgeon fish” in this study typically occur in much higher abundance than shortnose sturgeon, incorrect classification of echoes from these fish would lead to overestimation of the abundance of shortnose sturgeon. Notwithstanding this potential problem, the results of this preliminary study were promising, and further investigations to improve classifier performance are warranted.

Source Apportionment of Polychlorinated Biphenyls in the Tidal Delaware River

The Delaware River, similar to many surface water bodies throughout the United States, is impaired due to polychlorinated biphenyl (PCB) concentrations that exceed the federal water quality standard. A total maximum daily load (TMDL) for PCBs in the Delaware was promulgated in 2003 after construction of a detailed water quality model that relied upon estimated PCB loadings from sources such as wastewater treatment plant effluents, contaminated sites, and tributaries. The purpose of this project was to corroborate this loading estimate by analyzing ambient water column data on PCB concentrations in the Delaware River via positive matrix factorization (PMF) in order to identify covarying congener patterns that are, in theory, associated with sources. The PMF program identified six factors (covarying congener patterns) that appear to be associated with sources, such as sediment resuspension, contaminated sites, and wastewater effluents and combined sewer overflows (CSOs). PCB 11 was found to be a useful tracer for CSO/ wastewater inputs despite the fact that no known dye manufacturers exist in the watershed. This analysis generally corroborates the PCB loading estimate used in the water quality model.

Source identification of atmospheric PCBs in Philadelphia/Camden using positive matrix factorization followed by the potential source contribution function

The concentrations of gas-phase polychlorinated biphenyls (PCBs) in the atmosphere of the Camden, NJ, USA are elevated by as much as 20 times over regional background. These high PCB levels are a concern because they lead to atmospheric deposition loadings of PCBs to the tidal Delaware River that exceed the entire total maximum daily load (TMDL). Two models were applied to the atmospheric PCB concentration data from Camden in an attempt to identify the PCB source types and regions. Positive matrix factorization (PMF) was used to identify the source types. Four factors were identified which are thought to represent sources such as volatilized Aroclors and particle-phase PCBs. The potential source contribution function (PSCF) model was then used to identify the geographic source regions by examining the origination points for air parcels that result in high PCB concentrations at the Camden receptor site. The PSCF model for ΣPCBs indicates PCB source regions throughout the Philadelphia–Camden metro area, including portions of both Pennsylvania and New Jersey. The PSCF plots for the resolved PMF factors suggest that factors 1–4 show fewer distinct source regions, indicating that their sources are diffuse and/or lie very close to the receptor site. The PSCF plots for factors 2 and 3 reveal very different source regions. Factor 2 primarily arises from the city of Philadelphia, whereas factor 3 originates in southern New Jersey and south of Philadelphia. This study demonstrates the utility of the combined PMF/PSCF approach in identifying atmospheric PCB source types and regions.

Direct and Indirect Atmospheric Deposition of PCBs to the Delaware River Watershed

Atmospheric deposition can be an important source of PCBs to aquatic ecosystems. To develop the total maximum daily load (TMDL) for polychlorinated biphenyls (PCBs) for the tidal Delaware River (water-quality Zones 2-5), estimates of the loading of PCBs to the river from atmospheric deposition were generated from seven air-monitoring sites along the river. This paper presents the atmospheric PCB data from these sites, estimates direct atmospheric deposition fluxes, and assesses the importance of atmospheric deposition relative to other sources of PCBs to the river. Also, the relationship between indirect atmospheric deposition and PCB loads from minor tributaries to the Delaware River is discussed. Data from these sites revealed high atmospheric PCB concentrations in the Philadelphia/Camden urban area and lower regional background concentrations in the more remote areas. Wet, dry particle, and gaseous absorption deposition are estimated to contribute about 0.6, 1.8, and 6.5 kg year-(-1) sigmaPCBs to the River, respectively, exceeding the TMDL of 0.139 kg year(-1) by more than an order of magnitude. Penta-PCB watershed fluxes were obtained by dividing the tributary loads by the watershed area. The lowest of these watershed fluxes are less than approximately 1 ng m(-2) day(-1) for penta-PCB and probably indicates pristine watersheds in which PCB loads are dominated by atmospheric deposition. In these watersheds, the pass-through efficiency of PCBs is estimated to be on the order of 1%.

Trace Element Speciation and Behavior in the Tidal Delaware River

Measurements of dissolved As, Cr, Cu, and Se using species-selective techniques were made in the tidal freshwater Delaware River at four sites in July 1991, January 1992, and March 1992. Concentrations of dissolved As, Cr, and Se were generally higher in July than in March or January. Copper concentrations were relatively constant. Both As and Cu increased in concentration in the region of Philadelphia. Measurements of As, Cd, Cr, Cu, Pb, Ni, Se, and Zn in seston were made during the July 1991 and March 1992 sampling using both a total digest and a series of sequential leaches. A large fraction of most of the elements, in the order Cd>Zn>Pb≥Cu>Ni≥As>Cr>Se, was solubilized by weak acid. The remainding fraction, for elements where the acid leach was not complete, was released by a rigorous digestion with concentrated acids. Based on estimates of similar rivers, Pb and Zn appear to be substantially enriched in Delaware River seston compared to other rivers draining the same geological provinces. Arsenic, Se, and Cd in seston may be moderately enriched.

Temporal Trends in Abundance of Fish in the Tidal Delaware River

Water quality in the tidal Delaware River has improved dramatically over the last several decades. Areas near Philadelphia that were once anoxic and formed a pollution block to migratory fish passage now rarely experience dissolved oxygen concentrations less than 3 ppm. To assess whether these improvements in water quality led to increased abundance of juvenile fishes, data from a beach seine survey conducted annually since 1980 were examined. The number of species captured increased throughout the tidal river, but the increase was greatest in the areas downstream of Philadelphia, wheare water quality has improved the most. Abundance of juvenile striped bass and American shad, two important game species in the river whose migratory patterns make them susceptible to water quality problems, both increased more than, 1,000-fold during the last decade. Correlatations between the temporal abundance patterns of these species in the tidal Delaware River and in other East Coast systems were poor, suggesting that increases in their numbers were related more closely to improving conditions within the Delaware than to factors affecting coastal stocks.

Occurrence and Distribution of Shortnose Sturgeon, Acipenser brevirostrum, in the Upper Tidal Delaware River

Sampling in the upper tidal Delaware River between Trenton, New Jersey, and Philadelphia, Pennsylvania, from July 1981 through December 1984 demonstrated the existence of a significant population of shortnose sturgeon. The sturgeon aggregate in the river channel during daylight hours, especially in the area between Trenton and Florence, New Jersey (river km 211.8 to 198.8). Occurrence in the river downstream of Florence appears to be restricted by poor water quality during summer months. Sturgeon were present in the study area throughout the year, but largest numbers were collected from May though November. No spawning was observed during this study, but presence of males with milt suggests that spawning possibly occurs in the Trenton area. Preliminary population estimates (Peterson, Schnabel and Seber-Jolly) indicate an adult population of approximately 6,000–14,000 shortnose sturgeon occupying the upper tidal Delaware River.

Occurrence of Juvenile Atlantic Sturgeon, Acipenser oxyrhynchus, in the Upper Tidal Delaware River

Eighty-nine juvenile Atlantic sturgeon,Acipenser oxyrhynchus oxyrhynchus, including 10 recaptures, were collected, tagged and released in the upper tidal Delaware River between July 1981 and December 1984. All were captured in the river channel between Roebling and Trenton, New Jersey, using bottom-set experimental gill nets during daylight hours. The species was present from July through December and collected in increased numbers in the past two years. The fork lengths ranged from 284 to 862 mm (mean±SD = 516 mm±106 mm) and the weights from 140 to 4,250 g (mean±SD = 1,369 g±815 g). Ten juvenile Atlantic sturgeon were recaptured between September 1983 and December 1984 and were at large from one to 418 d. Recapture data suggest that these sturgeon utilize this area annually from July through December, possibly as a nursery. Juvenile Atlantic sturgeon appear to utilize the upper tidal portion of the Delaware River for a much longer period of time and at lower temperatures than in other river systems.

Problems and prospects in long and medium range weather forecasting

We investigate the ability to improve flood inundation forecasts at short- to medium-range (1–7 days) timescales through weather ensembles and statistical water surface elevation (WSE) postprocessing. To generate the flood inundation forecasts, a one-dimensional hydraulic model, namely the Hydrologic Engineering Center’s River Analysis System (HEC-RAS), is coupled to a regional hydrological ensemble prediction system (RHEPS). The RHEPS is comprised of: i) hydrometeorological observations; ii) weather ensembles from the National Centers for Environmental Prediction Global Ensemble Forecast System Reforecast version 2 (GEFSRv2); and iii) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM) as the hydrological model. The coupled RHEPS-hydraulic system is evaluated along the tidal Delaware River near the City of Philadelphia, Pennsylvania, U.S. For the evaluation, emphasis is placed on the tidal-riverine transitional zone of the Delaware River and the downstream propagation of hydrometeorological uncertainty through the flood inundation forecasts. The coupled system is used to generate hourly flood inundation forecasts at lead times from 1 to 7 days, over the period 2008–2013. Additionally, WSEs from the coupled system are statistically postprocessed using quantile regression (QR). Results show that the raw flood inundation ensemble forecasts exhibit higher skill than the deterministic ones. We also find that statistical postprocessing improves the skill of the raw flood inundation ensemble forecasts, with greater improvements at the longer lead times (>3 days). Overall, we find that both weather ensembles and statistical WSE postprocessing can be used to enhance the skill of flood inundation forecasts at short- to medium-range timescales. In turn, this may serve to enhance the spatial representation of flood forecasts several days in advance, which could contribute in the future to making flood forecast communication and warnings more effective.

Macrobenthos of the Tidal Delaware River between Trenton and Burlington, New Jersey

A study of the macrobenthos of the tidal Delaware River between Burlington and Trenton, New Jersey, included measurements of density and biomass for common species. Tubificidae (Limnodrilus) were dominant, comprising over 90% of all organisms taken in the 3-year study period. Density seemed to be a function of water temperature (20–25 C, optimal) and was greatest in late spring and early summer. Other common species were larvalProcladius culiciformis (Chironomidae) andCorbicula manilensis (asiatic clam).Procladius was most abundant in late summer just prior to and during emergence. The asiatic clam was in the process of colonizing the area and growth data have been calculated. Potential relationships between numbers and standing crop of the common organisms with sediment type, and seasonal changes were explored.