Short-term Field Measurements Research Articles

Linking marsh sustainability to event-based sedimentary processes: Impulsive river floods initiated lateral erosion of deltaic marshes

Salt marshes providing valuable services in buffering flooding risks are regarded as cost-effective coastal defense solutions. Given that eroding marsh cliffs will threaten the sustainability of these protective functions, there is a need for mechanistic understanding of cliff formation. Based on short-term field measurements together with satellite-derived dataset and a morphodynamic model, we determined the response of marsh lateral dynamics to event-based sedimentary processes in the Yellow River Delta, China. It was found that the Eastern Marsh with a cliff of ∼1.2 m in height significantly differed from the gentle Western Marsh in accretion pattern and lateral dynamics. Attributed to an artificial flood lasting ∼20 days in 2022, the Eastern Marsh platform experienced average vertical accretion of 23.3 mm, ∼5 times higher than the Western Marsh barely impacted by fluvial sediment supply. Although the accretion pattern ensured the overall vertical adaptability, Eastern Marsh has translated from a phase of rapid expansion to lateral retreat of ∼60 m/yr since 2018, whereas Western Marsh was relatively stable in recent decade. With a validated delta-marsh model, we showed that the observed disparities were attributed to different marsh edge morphodynamic responses to river flood sediment supplies. When Spartina alterniflora initially colonized, the Eastern Marsh platform was lower and the trapping efficiency could rise by ∼3 times than the present. Integrating with ten-fold increases in sediment loads, it was estimated that the large artificial floods in 2018 could contribute to a vertical growth approximating 30 cm at Eastern Marsh. Such episodic but rapid marsh accretion played a crucial role in initiating the development of marsh cliff. Driven by positive feedbacks between platform elevations and cumulative wave thrust, a series of event-based marsh sedimentation will promote long-term marsh loss caused by lateral retreat at sediment-starved systems. This study provides insights in predicting marsh sustainability and long-term evolutions under episodic sedimentary events.

A method for using crowd-sourced trajectories to construct control-independent fundamental diagrams at signalized links

This work presents a methodology for measuring traffic quantities from crowd-sourced trajectories for the purpose of estimating saturation flow rates. First, the observed trajectories are clustered to identify the signal programs that occur over the data collection period. Trajectories with known cycle lengths are accumulated on one space–time plot with their respective green start times at the origin, and then Edie’s generalized definitions of traffic variables are adapted to construct a full-scale fundamental diagram. The approach is tested empirically, and the averages and variances of the estimated quantities were within the expected ranges for each type of movement. Results from several movements were also verified against field measurements from a short video recording. The proposed method enables estimations of saturation flow rates over entire networks based on long-term datasets, instead of short-term field measurements. The approach is particularly advantageous for estimations under the unpredictable conditions associated with conflicting movements.

Wind-driven water level fluctuations drive marsh edge erosion variability in microtidal coastal bays

Marsh shorelines are retreating rapidly in coastal Louisiana, largely driven by wind waves attacking the marsh edge. The amount of wave power hitting the marsh is a major predictor for marsh retreat rates; however, marsh erodibility (erosion rate per unit of wave power) has a large spatial variability. Identifying the causes of this variability is essential to obtain more reliable predictions and to optimize marsh protection strategies. Here we investigate marsh edge erosion in a small (~3 km2) bay within Barataria Bay, LA, USA. Long-term (~140 years) erosion data and short term (~1 year) field measurements show that, for the same wave power, north-facing marsh edges erode twice as fast as south-facing marsh edges. A possible explanation might reside in the peculiar hydrodynamics of coastal Louisiana, where northerly winds are associated with low water levels and southerly winds are associated with high water levels. This causes south-facing shores to experience high water levels when being impacted by waves and north-facing shore to experience low water levels when being impacted by waves, which could subsequently affect marsh edge erosion in three different ways. First, south-facing shores experience a higher frequency of wave overshooting, which limits the ability of waves to cause erosion. Second, north-facing shores experience a higher frequency of waves impacting the highly erodible soil below the root mat, thus undercutting the marsh. Third, south-facing marsh edges have a higher elevation and a higher soil shear strength in the root layer (0–20 cm depth), likely because these shores receive more sediment during wave events. These three processes were combined into a single empirical correction to represent effective marsh erodibility and the correction was used in a 2D model of marsh edge retreat. The model accurately predicts marsh edge erosion and can be used to determine whether historical marsh loss was due to edge erosion or to other processes, such as ponding or drowning.

Pathways of Water and Sediment in the Biesbosch Freshwater Tidal Wetland

Diversion of water and sediment into drowning delta wetlands aims at renewed sediment accumulation for ecosystem regeneration and compensation of sea-level rise and soil subsidence. The success of such measures requires sound understanding of flow pathways and deposition patterns within wetlands and their feeding channels. This study aimed to (1) identify such pathways in a tidal freshwater wetland in the Netherlands, (2) determine the relative contribution of the two feeding rivers (Rhine and Meuse) to the water and sediment budget and (3) explore whether moving boat campaigns can contribute to a comprehensive understanding of the system. Bed level change was highest in newly developed areas, where equilibrium sets in. Sedimentation takes mainly place in channels close to the feeding rivers, where sediment becomes replenished each tidal cycle. Distal tidal channels receive only water poor in sediment during flood tide and experience erosion. Short term changes in suspended sediment load, measured during moving boat campaigns were generally consistent with average long-term changes in bed level. This means that short-term field measurements can not only be used to explain the processes, but also to predict the longer-term development of the major part of the study area.

The study of climate-responsive solutions in traditional dwellings of Bushehr City in Southern Iran

The present study aims to identify climate-responsive solutions used in traditional dwellings of Bushehr, a city in south west of Iran, and analyze the effects of these solutions in thermal comfort and energy consumption of these buildings in comparison to the modern ones. After selection of the sample buildings and short-term field measurements from local climate throughout the year, the field data collected was used in simulation and comparison of the traditional and the contemporary sample buildings. All buildings were simulated with Design Builder software under natural ventilation conditions as a passive solution in moderate periods of the year while split air-conditioning systems were used during hot and humid periods. The findings show that shading, proper materials in exterior walls and natural ventilation in traditional dwellings are the primary factors in improving comfort conditions and reducing cooling loads; and accordingly, discomfort hours decreased by 12–34% and the cooling energy consumption was also reduced by 26–46% in these dwellings. Better thermal comfort and less energy consumption in traditional dwellings of Bushehr show that the integrated climate-responsive solutions used in these dwellings have well-responded to the local climate characteristics in this city and have contributed to the formation of climate-responsive buildings in the severe climate conditions of this region. Today it is possible to reuse these buildings as residential spaces with satisfactory thermal comfort conditions and less energy consumption compared to the contemporary ones and the solutions used in these dwellings can also be used to design new climate-responsive buildings.

Improved hydrological model parametrization for climate change impact assessment under data scarcity - The potential of field monitoring techniques and geostatistics.

According to current climate projections, Mediterranean countries are at high risk for an even pronounced susceptibility to changes in the hydrological budget and extremes. These changes are expected to have severe direct impacts on the management of water resources, agricultural productivity and drinking water supply. Current projections of future hydrological change, based on regional climate model results and subsequent hydrological modeling schemes, are very uncertain and poorly validated. The Rio Mannu di San Sperate Basin, located in Sardinia, Italy, is one test site of the CLIMB project. The Water Simulation Model (WaSiM) was set up to model current and future hydrological conditions. The availability of measured meteorological and hydrological data is poor as it is common for many Mediterranean catchments. In this study we conducted a soil sampling campaign in the Rio Mannu catchment. We tested different deterministic and hybrid geostatistical interpolation methods on soil textures and tested the performance of the applied models. We calculated a new soil texture map based on the best prediction method. The soil model in WaSiM was set up with the improved new soil information. The simulation results were compared to standard soil parametrization. WaSiMs was validated with spatial evapotranspiration rates using the triangle method (Jiang and Islam, 1999). WaSiM was driven with the meteorological forcing taken from 4 different ENSEMBLES climate projections for a reference (1971-2000) and a future (2041-2070) times series. The climate change impact was assessed based on differences between reference and future time series. The simulated results show a reduction of all hydrological quantities in the future in the spring season. Furthermore simulation results reveal an earlier onset of dry conditions in the catchment. We show that a solid soil model setup based on short-term field measurements can improve long-term modeling results, which is especially important in ungauged catchments.

The influence of changes in wind patterns on the areal extension of surface cyanobacterial blooms in a large shallow lake in China

It has been hypothesized that climate change will induce the areal extension of cyanobacterial blooms. However, this hypothesis lacks field-based observation. In the present study both long-term historical data and short-term field measurement were used to identify the importance of changes in wind patterns on the cyanobacterial bloom in Lake Taihu (China), a large, shallow, eutrophic lake located in a subtropical zone. The cyanobacterial bloom mainly composed of Microcystis spp. recurred frequently throughout the year. The regression analysis of multi-year satellite image data extracted by the Floating Algae Index revealed that both the annual mean monthly maximum cyanobacterial bloom area (MMCBA) increased year by year from 2000 to 2011, while the contemporaneous cyanobacterial biomass showed no significant change. However, the correlation analysis shows that MMCBA was negatively correlated with wind speed. Our short-term field measurements indicated that the influence of wind on surface cyanobacterial blooms is that the Chlorophyll-a (Chla) concentration is fully mixing throughout the water column when the wind speed exceed 7ms−1. At lower wind speeds, there was vertical stratification of Chla with high surface concentrations and an increase in bloom area. The regression analysis of wind speed indicates that the climate has changed over the last decade. Lake Taihu has become increasingly calm, with the decrease of strong wind frequency between 2000 and 2011, corresponding to the increase in the MMCBA over time. Therefore, we conclude that changes in wind patterns related to climate change have favored the increase of cyanobacterial blooms in Lake Taihu.

Diurnal changes in photosynthetic activity of the biological soil crust and lichen: Effects of abiotic factors (Petuniabukta, Svalbard)

In polar ecosystems, primary producers have to cope with a very harsh climate that limits the time available for growth and biomass production. In this study, diurnal measurement of photosynthetic processes in biological soil crust and a lichen were carried out in Petuniabukta, Spitsbergen. For field measurements, a method of induced fluorescence of chlorophyll was used. Measurements of photosynthetic activity were taken as repetitive measurements of effective quantum yield of photosystem II (ΦPSII). The short-term field measurements were carried out for 10 days in summer 2014. ΦPSII was recorded each 5 minutes as well as microclimatic data (air temperature, air humidi-ty, photosynthetically active radiation - PAR). The microclimatic parameters were recorded by a datalogger. In general, physiological activity of both biological soil crust and a lichen showed daily courses. Tested lichen was Cladonia rangiferina and the most dominant species in biological soil crust was Nostoc sp. Typically, most of ΦPSII values ranged 0.6 – 0.7 in both model organisms. The results have shown that photosynthetic activity was strongly correlated with all observed abiotic factors in both study objects. Particularly important was the relation found between PAR and ΦPSII in biological soil crust. When the biological soil crust was exposed to high PAR doses of irradiation (about 2300 µmol m-2 s-1) photoinhibition of primary processes of photosynthesis was observed as ΦPSII decrease, while photosynthetic activity of lichen remained at same level. Furthermore, it has been demonstrated increasing that in situ photosynthetic activity increased in both biological soil crust and lichen with a decrease in temperature.

Internal Surface Temperatures Short-Term Measurement in the Selected Living Room with Fireplace

Fireplaces are still popular and they are mostly used as a supplementary heating source. On the other hand, they bring back to interior some temperature disproportion. The article reports the results of short-term field measurements in two selected homes with dissonant fireplaces and with different level of thermal performance. The measurements investigated the increase and decrease of internal surface temperature on external wall during fireplace operation. It was found, that in a case of preheated interior with high air temperature level, there is a big difference in the dependence of surface temperature on air temperature for irradiated and non - irradiated surface of the external wall.

The Analysis of Low Noise Protection Barriers Influence on Tram Traffic Noise Levels

Abstract The paper describes the analysis of tram traffic noise situation in residential areas in the vicinity of Drzic Avenue, one of the major routes between the northern and southern part of the Croatian capital city Zagreb, and the effect of low barriers placed by the tracks on tram noise mitigation. In order to evaluate the effect of planned protection measure, noise models were produced and verified with short-term field measurements. Calculations were conducted by means of noise prediction software, using European interim noise prediction method and 3D model of analyzed area. Finally, the results of noise calculations for existing tram traffic situation and planned measure of protection are presented on noise maps.

Photosynthetic activity in three vascular species of Spitsbergen vegetation during summer season in response to microclimate

Abstract Diurnal measurements of photosynthetic processes, effective quantum yield of photosystem II (ΦPSII), photosynthetic electron transport rate (ETR) were done in three dominant species of Arctic tundra (Silene acaulis, Dryas octopetala, Salix polaris) in Petuniabukta, Spitsbergen. Daily courses of net photosynthesis (PN) were calculated from chlorophyll fluorescence data and daily photosynthesis evaluated. The short-term field measurements were carried out in summer 2009, and 2010. Fluorometric parameters (ΦPSII and ETR) weremeasured each 5 minutes as well as microclimate characteristics of the site for 10 (2009) and 8 days (2010), respectively. In all species photosynthetic ETR was well related to incident photosynthetically active radiation and leaf temperature. In general, D. octopetala exhibited slightly lower ETR than the other two species. Estimated maximum photosynthetic rate (PNmax) reached 17.6, 21.4, and 22.9 μmol CO2 m-2 s-1 for S. polaris, S. acaulis, and D. octopetala, respectively. Daily photosynthesis reached comparable values in all species, D. otopetala, however, exhibited slightly lower values than the other two species both for overcast and fully sunny days (3.9 and 13.4 mmol CO2 m-2 d-1, respectively). The range of daily photosynthesis for S. polaris and S. acaulis studied, reached the ranges of 4.6-6.9 and 14.6-15.2 mmol CO2 m-2 d-1 for overcast and fully sunny day, respectively.

The partitioning of the total sediment load of a river into suspended load and bedload: a review of empirical data

The partitioning of the total sediment load of a river into suspended load and bedload is an important problem in fluvial geomorphology, sedimentation engineering and sedimentology. Bedload transport rates are notoriously hard to measure and at many sites only suspended load data are available. Often the bedload fraction is estimated with rule-of-thumb methods such as Maddock’s Table, which are inadequately field-tested. Here the partitioning of sediment load for the Pitzbach is discussed, an Austrian mountain stream for which high temporal resolution data on both bedload and suspended load are available. The available data show large scatter on all scales. The fraction of the total load transported in suspension may vary between zero and one at the Pitzbach, while its average decreases with rising discharge (i.e. bedload transport is more important during floods). Existing data on short- and long-term partitioning is reviewed and an empirical equation to estimate bedload transport rates from measured suspended load transport rates is suggested. The partitioning averaged over a flood can vary strongly from event to event. Similar variations may occur in the year-to-year averages. Using published simultaneous short-term field measurements of bedload and suspended load transport rates, Maddock’s table is reviewed and updated. Long-term average partitioning could be a function of the catchment geology, the fraction of the catchment covered by glaciers and the extent of forest, but the available data are insufficient to draw final conclusions. At a given drainage area, scatter is large, but the data show a minimal fraction of sediment transported in suspended load, which increases with increasing drainage area and with decreasing rock strength for gravel bed rivers, whereby in large catchments the bedload fraction is insignificant at ~1%. For sand bed rivers, the bedload fraction may be substantial (30-50%) even for large catchments. However, available data are scarce and of varying quality. Long-term partitioning varies widely among catchments and the available data are currently not sufficient to effectively discriminate control parameters.

Nearshore Impacts of Dredging for Beach Nourishment

A methodology is presented for predicting the impacts of nearshore dredging on shoreline change, using numerical models for waves, currents, and shoreline change. The dredge pit, outside of the surf zone, was assumed to be steady state, but alters waves reaching the surf zone. The methodology accounts for the transformation of directional wave energy spectra due to spatial gradients in both mean currents and bathymetry, wind inputs, and energy dissipation via several mechanisms. The wave transformation model SWAN (Simulating Waves Nearshore) was used to simulate waves at Folly Island, S.C., which served as the test case. Wave model results were validated using short-term field measurements at three locations. Longer-term (1 year) simulations were driven using hindcast wave and wind data. Velocity fields and tidal stages were simulated using the hydrodynamic model Environmental Fluid Dynamics Code in two-dimensional mode, after calibrating with field measurements. Wave model results were used to estimate longshore sediment transport and shoreline change due to longshore gradients of the longshore sediment transport rate. Empirical sediment transport coefficients were chosen to match model results to measured beach volume changes derived from beach profile data. The calibrated model was then used to predict impacts of dredging on long-term shoreline change. Results reproduced observed trends of erosion and accretion along approximately 90% of the shoreline.

Population dynamics of a tropical palm: use of a genetic algorithm for inverse parameter estimation

The tropical palm species Iriartea deltoidea is an important resource in Amazonian Ecuador. Population models, based on short-term field measurements, have been used to analyze management scenarios for Iriartea sustainable harvesting. An existing matrix population model for Iriartea in secondary and mature forests could not adequately simulate the population dynamics from clearing to 30 years or more. In order to find a better model of the Iriartea population, we used inverse analysis with two optimization techniques (Golden Section search and genetic algorithm (GA)) to find fecundity and seedling demographic parameters that best matched the observed secondary forest (30 years after clearing) and mature forest size class distributions. Re-estimation of fecundity using the Golden Section optimization resulted in a good match to seedling numbers, but a poor fit for other size classes. Genetic algorithm optimization of fecundity and seedling survival and transition parameters found good fits from clearing to age 30 with an exponential or density-dependent model. In order to find a single model that described the population trajectory from clearing to mature forest, we used the genetic algorithm to best fit the observed size class distributions at age 30 and for the mature forest (assumed ages of 65–150 years). The genetic algorithm produced plausible density-dependent models for each of the assumed mature forests ages. Simulated seedling demographic parameters 40–60 years after clearing were similar to field estimates from 30-year-old and mature forest populations.

The behaviour of nearshore bars on the time scale of years: a conceptual model

Abstract Soundings of the sandy Dutch coast have demonstrated the presence of a multiple bar system that exhibits cyclic, offshore-directed migration on the time scale of years (medium-term). A cycle comprises bar generation, interannual offshore migration and decay. In this paper we propose a conceptual model in which we qualitatively outline the relationships between short-term (hourly) process knowledge (waves, currents, sediment transport), based on a 15-week data set of near-bed hydrodynamics obtained in the multiple bar system of Terschelling (the Netherlands), and medium-term bar behaviour. The short-term process knowledge is aggregated to the medium-term by combining probabilistic characterisations of medium-term wave conditions and sediment transports estimated from the short-term field measurements. Essential to the conceptual model is the observed cross-shore change in short-term conditions that dominate medium-term onshore and offshore sediment transport (〈q〉on and 〈q〉off, respectively). In the cross-shore direction, the conditions contributing most to 〈q〉on change from predominantly breaking situations outside the bar zone to mainly non-breaking conditions on the beach. In contrast, 〈q〉off remains restricted to breaking conditions over the entire profile. In the model we qualitatively describe how this cross-shore change in the forcing conditions results in interannual offshore bar migration, bar decay and the onset of the next cycle. As such, our model may serve as a first step towards a more coherent, quantitative model on medium-term periodic bar behaviour.

Biogeochemical and physical controls of nitrogen fluxes in a highly dynamic marine ecosystem—model and network flow analysis of the Baltic Sea

Time, space and ecological organisation are key features of an ecosystem that are rarely explored simultaneously. A dynamic coupled physical–biogeochemical model, with a high vertical and temporal resolution that describes the large-scale hydrography and nitrogen dynamics of the Baltic proper has been used as a tool to explore these scales in a flow network analysis of an ecosystem. The ‘sampling’ of nitrogen concentrations and flows in this ecosystem model can be done with a much higher frequency in space and time than is practically possible in the sea. The model can also be used to follow salt and water fluxes. Thus, it was also possible to evaluate the relative importance of biogeochemical and physical processes. Measures of total system throughput (TST), which is intended to be an overall system attribute, suggest that the physical contribution to nitrogen fluxes is minor compared with those caused by biogeochemical processes. However, measures of material cycling estimated as Finn cycling index (FCI), which also is intended to capture overall system performance, show variations that can be explained to a great extent by the physical contribution. This demonstrates the difficulties to separately analyse the contributions of physical versus biogeochemical processes on the same levels of organisation. Input–output analyses show only minor differences when comparing the system in steady state and in dynamical mode. The internal spatially resolved time characteristics of nitrogen and salt, in our case measured as residence time, shows slightly different values for the system, when comparing short and long time scales, that it is questionable to speak about long term means. The turnover time for salt shows, a little surprisingly, the opposite of what was earlier expected, i.e. longer turnover for the surface layers and shorter turnover for bottom layers. The residence time, calculated for a dynamic system, shows that the expected time for a unit of nitrogen to reside in the system is highly dependent on when during the year it is entered. If one unit of nitrogen is enterering in the spring–early summer the residence time is slightly less than a year. If entered in autumn–winter, the unit of nitrogen will reside about a year and a half. The large temporal and spatial variations in ecosystem properties, measured in the model also illustrate the great difficulties to extrapolate observations from short-term field measurements to an ecosystem scale

Rates of aeolian transport on a beach in a temperate humid climate

Short term field measurements of aeolian transport, using a saltiphone, indicate that actual rates of transport deviate considerably from the potential rates predicted by transport equations. When examined in detail, however, potential rates are approached during special conditions: mostly when the wind blows offshore, parallel or slightly oblique to the beach and relative humidity is below 85%. Also, the potential rates of transport may be approached when wind speeds considerably exceed threshold speed, even during showers. The main cause of the large deviation of actual from potential rates is in the absence of transport during very wet conditions (prolonged rainfall) regardless of wind speed, and the variation of threshold velocity with time. The threshold velocity increases during wet conditions, with onshore winds or because of the presence of algae. Therefore, potential transport is defined as the transport optimum. To predict the actual rates of transport accurately, insight into the variation of the threshold velocity is essential. Aeolian transport of sand seems to be related to moderate events and not to extreme events, conforming to the principle of magnitude and frequency.

Particulate and nicotine sampling in public facilities and offices.

The purpose of this study was to characterize and measure indoor air quality in public facilities and office buildings. The pollutants of interest were particulate matter smaller than 2.5 microns in diameter, PM-2.5, and environmental tobacco smoke (ETS). Integrated PM-2.5 samples were taken on Teflon membrane filters using Harvard Aerosol Impactors as a pre-size selector. Filters were analyzed by gravimetric analysis. Nicotine, which was used as a marker for ETS, was collected on sodium-bisulfate-impregnanted, glass-fiber filters and was analyzed by gas chromatography. Twenty-one structures were monitored in Metropolitan Boston. Measured particle concentrations ranged from 6.0 micrograms/m3 to about 550 micrograms/m3. Nicotine concentrations were as high as 26 micrograms/m3 in a designated smoking room. Real-time measurements were also taken using two types of nephelometers; a Handheld Aerosol Monitor (HAM) and a Miniature Real-Time Aerosol Monitor (MINIRAM). Short-term field measurements with these instruments correlated better with the integrated PM-2.5 concentrations in smoking locations than with concentrations in non-smoking areas.

Morphology, Surface Characteristics, and Flow Velocity of Soler Glacier, Patagonia

The morphology and surface characteristics of the Soler Glacier, Patagonia, were analyzed utilizing vertical aerial photographs taken in 1984 and 1986, coupled with a field survey. The bedrock topography was measured in a gravimetric survey. The three subglacial cross-profiles indicate that a longitudinal subglacial ridge runs roughly along the median of the glacier. The major surface features recognized include an ablation medial moraine, ice-cored lateral and supraglacial moraines, ice mounds, crevasses, supraglacial stream systems, and five sets of ogive patterns. Ogive band spacings indicate that ice flow velocities range from less than 100 m yr-1 near the snout to more than 300 m yr~1 below icefalls and bedrock cliffs. These values generally agreed well with the distance ice mounds moved and the velocity inferred by extrapolation of two short-term field measurements.