Flow Sediment Research Articles

Estimation of Suspended Sediment Concentration from Remote Sensing and In Situ Measurement over Lake Tana, Ethiopia

Discharge from basins joining a lake is the main factor determining the lake volume and sediment inflow to the lake. Suspended sediment is an important parameter for describing the water quality of aquatic ecosystems. Lake Tana is an important and the largest lake in Ethiopia for the local ecological system. However, environmental change and anthropogenic activities in the area threaten its water quality. The conventional methods of suspended sediment concentration (SSC) observation are unable to determine and compare spatial and temporal SSC patterns for the lake over a period of years. Remote sensing methods have made it possible to map SSC. The objective of this study is to characterize the spatial and temporal distribution of suspended sediment of Lake Tana using in situ measurement and remote sensing applications and specifically to develop a relationship between in situ and remote sensing observation to retrieve suspended sediment concentration and map the spatal distribution of SSC. This study used MODIS‐Terra and in situ data to characterize the spatial and temporal distribution of SSC in the rainy season. Four sampling campaigns (20 samples per campaign) were carried out on Lake Tana, and the first three sampled campaigns on May 11–13, 2018, June 08–10, 2018, and July 15–17, 2018, were used for calibration of regression models. MODIS‐Terra reflectance in NIR was found best related to in situ water quality data and varies linearly with SSC (r2 = 0.81) and turbidity (r2 = 0.85). Secchi disc depth (SDD) found the best fit for a power relation with NIR band reflectance (r2 = 0.74). The MODIS‐Terra reflectance in red was found to be poorly related to in situ measurements. The relation in NIR reflectance was validated using the LOOCV (leave‐one‐out‐cross‐validation) technique and the fourth sampled data set collected on August 12–14, 2018. Developed models are validated with RMSE of 42.96 mg/l, 14.6 NTU, and 0.17 m, ARE of 23.3%, 27.6%, and 12.4%, and RRMSE of 25.1%, 44.5%, and 29.6% for SSC, turbidity, and SDD, respectively, using LOOCV. The equation was also validated using August 2018 collected data sets with RMSE of 87.6 mg/l, 11.7 NTU, 0.08 m, ARE of 20.8%, 25.9%, and 28.8%, and RRMSE of 17.8%, 20.5%, and 27.9% for SSC, turbidity, and SDD, respectively. Applying the developed regression model, a 10‐year time series of SSC from 2008–2017 for May‐August was estimated and the trend was tested using the Mann–Kendall trend test. It was found that an increasing trend was observed from the period 2008 to 2017. The result shows that satellite data like the MODIS‐Terra imagery could be used to monitor and obtain past records of SSC with the developed equation. The increasing SSC can be reduced by implementing selected management practices in the surrounding watersheds of the lake to reduce nutrient and sediment inflow.

Types, characteristics, distribution, and genesis of pockmarks in the South China Sea: insights from high-resolution multibeam bathymetric and multichannel seismic data

ABSTRACT Ubiquitous pockmarks in continental margins are important to understand the tectonic and sedimentary history and flow activity of their host margins. The study of an extensive field of pockmarks in the South China Sea (SCS) is important both scientifically and economically, for the exploration of oil, gas, and gas hydrate resources and the prevention and control of marine geological disasters. We report our new findings on the characteristics, distribution, and genesis of pockmarks in the SCS based on interpretation of high-resolution multibeam bathymetric data and multichannel seismic profiles collected in the past decade. Three pockmark fields (total area 572,824 km2), are recognized in the northern, western, and southern continental margins of the SCS. The pockmarks are highly variable in shape: circular, elliptical, crescent-shaped, elongated or forming a chain in plan view and U-, V- or W-shaped in cross-section. Pockmarks are normally 10–200 m in diameter, with maximum diameters/axial lengths of 7.3 km for circular, 5.5 km for elliptical, 8.6 km for crescent-shaped, 9.5 km for elongated, and 30 km for chain-type pockmarks. Pockmarks are normally less than 35 m deep, with a maximum depth of 341 m at the southwestern SCS margin. These pockmarks might have originated from methane seepages or from pore fluids from deeper sources, which migrated vertically along gas chimneys, mud diapirs, mud volcanoes, faults or buried channels. In addition to possible structural controls, the pockmark morphologies are affected by bottom currents.

Sediment particle selectivity and its response to overland flow hydraulics within grass strips

AbstractParticle selectivity plays an important role in clarifying sediment transport processes in vegetative filter strips (VFS). 10‐m long grass strips at slopes of 5° and 15° were subjected to a series of sediment‐laden inflows experiments with different particle sizes to investigate the sediment transport and its response to overland flow hydraulics. The inflow sediments came from local soil, river‐bed sand, and mixed, with median particle size d50 of 39.9, 207.9 and 77.4 μm, respectively. Three independent repeated experiments were carried for each treatment. The results show that when the sediment trapping lasted for a certain length of time, the re‐entrainment of some small‐sized particles was greater than the deposition; that is, net loss occurred, which was not erosion of the original soil. Net loss of particles is mainly determined by the particle diameter. The coarser the inflow sediment particles and/or the steeper the slope, the coarser the particles can be net lost. Deposited sediment causes the VFS bed surface to become smooth and hydraulic resistance decrease exponentially. Unit stream power P is more suitable than shear stress τ of overland flow to be used to describe the process of sediment particle transport in VFS. The relationship between P and d50 of outflow sediment is very consistent with the form of power function with a constant term. These results are helpful to understand the physical process of sediment transport on vegetation hillslopes.

Analysis of Slope Stability for Kaande Landslide of Phewa Watershed, Pokhara, Nepal

Phewa watershed of Kaski, Nepal is constantly facing landslides and soil erosion problems. Andheri Khola sub-basin of Phewa watershed accounts the maximum amount of sediment inflow into Phewa Lake. Therefore Kaande Landslide of Andheri Khola sub-basin, located between Deurali and Paundur villages at the source zone of Andheri Khola is chosen for the slope stabilization to control the sediment flow. The main objective of the study was to analyze the slope stability condition of the landslide area for which the whole landslide area was divided into eight zones starting from the crown to the toe based on the major parameters like soil/rock type, slope inclination, spring source and surface water on the basis of field observation. The factor of safety of each zone was calculated based on stability analysis of an infinite slope of cohesive soils. Sieve analysis result shows the landslide area has coarse grained structure (gravel and sand) dominant. The factor of safety of the landslide was found to be from 0.281 to 0.710. The field assessment and factor of safety reveals the Kaande landslide to be unstable and further possibilities of landslides and soil erosion in the future. For mitigating the hazard, eco-friendly soil bio-engineering measures such as direct seeding of grasses/shrubs, grasses/shrubs/trees plantation, brush layering, and gabion wire bolster cylinders are recommended for slope stabilization based on the optimal techniques guidelines of Mercy Corps Nepal, 2014. It is recommended to apply the proposed mitigation measures as early as possible to prevent the further landslide hazard.

Landslide‐dammed lake sediment volume calculation using waterborne ERT and SONAR profiling

AbstractLake sediment volume calculation is a challenging task, namely in cases when detailed drilling is complicated, expensive, or impossible, information on the pre‐sedimentation surface unavailable, and record of siltation rate non‐existent or too short. This study shows how waterborne, non‐invasive geophysical survey, such as electrical resistivity tomography (ERT) can be very effective in acquiring the missing data, namely when combined with sound navigation ranging (SONAR) water depth measurements and supported by information from auxiliary sources. However, ERT surveying in water environment requires specific approaches, as we illustrate on the case of the Mladotice lake study. The lake was created after a landslide in May 1872, and since its formation, the depth has gradually decreased due to sedimentation. We have reconstructed the original surface, calculated the sediment volume, and compiled information on sedimentation to estimate its remaining life span. To achieve this, we measured nine waterborne ERT profiles across the lake. To reach the necessary depth, all ERT profiles were extended on land and crossed the lake using custom‐built flotation pads. ERT profiling was combined with SONAR depth measurements, historical bathymetric surveys, borehole core analysis, sediment flux measurements, volumetric calculations, and water conductivity probing. The study has achieved three main results. First, practical applicability and advantages of stationary waterborne ERT profiling in combination with bathymetric sounding were demonstrated. Second, the original lake volume and accumulated sediment was calculated. We estimate that the volume of lake sediment is 187 000 m3, two‐thirds of the original lake volume (over 275 000 m3). Finally, based on three volumetric data sets from 1972, 2003, and 2017, and recent monitoring of the sediment inflow, we propose scenarios of lake filling and its future development. Most interestingly, the sedimentation rate has decreased significantly in the last 20 years, suggesting that the lake may survive much longer than hitherto expected. © 2020 John Wiley & Sons, Ltd.

DETERMINATION MINING ZONE OF NON-METAL MINERAL AND ROCK BASED ON SEDIMENT INFLOW AND OUTFLOW IN THE BODRI RIVER KENDAL REGENCY

ABSTRACTLocal traditional mining in the Bodri River Kendal regency increasingly concerned, this is of course if left unchecked will damage the river body, river channel, causing landslides, can even disrupt the stability of water buildings such as weirs and bridges. The purpose of this research is as an effort to Determine Non-Metal and Rock Mineral Mining Zonation Based on the Inflow and Outflow of Sediment in Bodri River of Kendal Regency, to obtain the areas which are allowed to be mined and the mining volume. This research is descriptive qualitative by doing direct observation, interview and documentation. Descriptive method is a method used to examine the status of human groups, an object, a condition and a system of thought and events that will occur. The purpose of this study is to create an explorative, systematics, factual and accurate facts on the specific case. The research results are sediment inflow to the Bodri river is 103.327,40 ton/year, whereas the outflow is 379.459.46 ton/year, which mean the river morphology has serious problem caused by the mining activity. Keywords: Zoning, Mining, Non-Metal Material and Rocks, Sediment

Hydrodynamics and deposition in lacustrine shallow-water delta front: A combination of numerical simulations and modern sedimentation measurements

With the exploration of tight oil and gas, shallow-water deltaic reservoirs have been attracting more and more attention. The sedimentary architecture of a shallow-water delta shows distinctive differences with that of a deep-slope delta. These differences may be associated with the mechanism and characteristics of the deposition in the area where the sediments unloaded. Based on modern sedimentary research of the Poyang Lake in China, this paper focuses on the processes of river flow entering a lake with a low dip angle. We conducted six sets of numerical simulations with different initial sedimentary flow velocities using Fluent software for analyzing the hydrodynamics and the sediment transportation in the shallow-water delta. We combined the simulation results with an analysis of the geomorphology of the Gangjiang Delta to reveal the deposition along the shoreline of the lacustrine shallow-water delta. The numerical simulation shows that the shallow-water delta is dominated by bed friction with an extensive hydrodynamical boundary layer. The bed shear stress, which varies with the changes in river flux, dominated the sediment transport and deposition at the shallow-water delta front, where the effluent flow mixes with lake water. The distributary channels show characteristics of repeatedly occurred erosion, scouring, filling, and reoccupation. We argue that the depositional characteristics are associated with the changes in bed shear stress controlled by variation of flow velocity. Mouth bars are less likely to grow to a reasonable scale because of the seasonal scouring of extreme floods. Moreover, the lake flow potentially reworks the mouth bars. Consequently, mouth bar deposits were difficult to preserve as hydrocarbon reservoirs in ancient shallow-water delta.

Evaluation of the sand trap performance of the Pengasih weir during the operational period

Sedimentation is the main trigger in reducing the capacity of the irrigation channel. The weir is equipped with a sand trap, to withstand the volume of sediments originating from the upstream area, some of which enter the irrigation intake. The sand trap is designed with sufficient width and sloping energy slope, allowing sediment to settle. The Pengasih Weir, located in Kulonprogo Regency, is one of the weirs that is equipped with a sand trap building. The Pengasih Weir and the sand trap were built-in 1972. With the development of current conditions, it is necessary to evaluate the performance of the sand trap of The Pengasih Weir. In this study, the evaluation of sand trap performance is reviewed during the operational (settling) period. The result showed that the Meyer-Peter Muller formula can be used as an approach in the calculation of the amount of sediment transport and also to estimate the settled volume. It is recommended to flush the sand trap in between 184.922 days. The average value of trap efficiency was 0.89%. It can be concluded that the Pegasih Weir sand trap design still has good performance in settling the sediment inflow.

Characterizing detachment and transport processes of interrill soil erosion

Detachment and transport processes of interrill soil erosion are not yet fully understood and quantified due to their complexity. Understanding these processes and their interaction is essential to developing effective interrill erosion prediction models. Thus, the objectives are to (1) identify detachment-limiting and transport-limiting regimes by comparing measured total soil splash with total sediment load of flow wash, (2) estimate relative importance of raindrop-driven and flow-driven transports under selected flow conditions using a novel experimental protocol, and (3) test widely used erosion equations for use in both detachment-limiting and transport-limiting regimes under the experimental conditions never before used. Sediment discharge and raindrop splash were separately collected from two plots with a 2.5-cm gap between them. Three rainfall intensities of 60, 90, and 120 mm h−1 were applied to three slopes of 9, 18, and 27% under two cover treatments of screen and tarp. Screen cover is to simulate crop canopy for dissipating raindrop energy, which is to control upslope sediment inflow by reducing raindrop detachment without modifying runoff rates. Tarp cover is to control both water and sediment inflows by varying slope length. Results showed that total raindrop splash in the entire plot during an event was less than total flow wash in the screen treatment, indicating detachment-limiting scenarios. However, total raindrop splash was greater (less) than total wash at the 9% (27%) slope in the tarp treatment, indicating transport-limiting (detachment-limiting) cases. The results indicated that raindrop-impacted flow might be able to detach soil in some cases. This finding runs counter to the common wisdom that soil detachment in interrill erosion is solely caused by raindrop impact. If raindrop-impacted flow can detach soil, the determination of limiting process by direct comparison between splash and wash loads seemed overly simplistic. Raindrop-driven transport was estimated for the first time by a means of dissipating raindrop impact energy in this study. Raindrop-driven transport was found to increase with rainfall intensity and slope gradients. Stream power and an empirical multiplication-of–factor equation performed well in predicting interrill sediment delivery under all erosion regimes, suggesting that it is unnecessary to develop distinct predictive equations for different interrill erosion regimes.

Assessment of Performance of a Groin Constructed on Puducherry Coast - A Case Study

Dhanya, S.; Mohan, R.; Mullai Vendhan, K.; Ramana Murthy, M.V., and Sajeev, R., 2020. Assessment of performance of a groin constructed on Puducherry coast - A case study. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 84-91. Coconut Creek (Florida), ISSN 0749-0208.India, having coastline of about 7500 kms, is facing severe problems of erosion, threatening millions of lives. Construction of planned ports, harbours, and industries accelerate the erosion and degrade the environment along India's coastline. The reduced rainfall, due to changes in the monsoon pattern over the years, has in turn lessened the sediment inflow into the oceans. This reduction in the sediment flow leads to considerable erosion along the coastlines. Groins are typically built to stabilize a number of natural or manmade beaches against erosion, mainly due to a net loss of beach material. The influence of a groin is accretion of the beach material on the updrift side and erosion on the downdrift side. Puducherry, a Union Territory, is facing severe coastal erosion problems along some of the stretches, especially to the north of Puducherry harbour. In this study, the status and impact of a 60 m long groin constructed at Vaithikuppam, on Puducherry coastline is studied. A coupled and fully integrated 2D model for waves, currents and sediment transport is used for the assessment. The hydrodynamic processes and morphological stability near the groin are studied using field observations and bathymetric data. The numerical model results were validated and found to be in good agreement with the field data. The hydrodynamic conditions and sediment transport patterns are predicted using the model results and the impact of the groin on the morphological characteristics are established and presented.

Blue Crab Abundance and Survival in a Fragmenting Coastal Marsh System

Louisiana’s coastal marshes are becoming increasingly fragmented due to sea level rise, subsidence, reduced sediment inflow from the Mississippi River, and saltwater intrusion. Many commercially and recreationally fished species rely on the marsh system as nursery habitat, and the resilience of species to further marsh loss and marsh fragmentation is uncertain. We examined the impacts of marsh fragmentation on the blue crab, Callinectes sapidus, a species supporting one of the largest fisheries in coastal Louisiana and which uses marsh edge as nursery habitat. Juvenile and adult abundances were quantified in multiple habitats (bare sediment, marsh edge, and submerged aquatic vegetation [SAV]) within an actively fragmenting coastal marsh. Adult blue crabs were sampled using crab pots, while juveniles were sampled using a throw trap. In general, blue crab density was unrelated to marsh fragmentation, but was instead related to local-scale patterns of habitat availability, including presence and type of vegetation. In tethering experiments to examine predation rates on juvenile blue crabs across habitats, predation rates were lowest in SAV compared with marsh edge or bare sediment. While direct effects of marsh fragmentation on local-scale patterns of blue crab abundance were not observed, marsh fragmentation will likely have indirect effects on blue crab populations through changes in habitat availability. Unless SAV expands into newly created open water areas, providing an alternative nursery habitat for blue crabs, continued marsh fragmentation and loss are expected to have negative impacts on blue crab populations and fisheries through a decrease in available nursery habitat.

Tendency of Runoff and Sediment Variety and Multiple Time Scale Wavelet Analysis in Hongze Lake during 1975–2015

Hongze Lake plays a key role in flood and waterlogging prevention, analyzing the variation process and characteristics of multi-time scales will have a great practical significance to water resources management and regulation in the Huaihe River basin of China. This research proposed a combinatorial mutation test method to study the interannual variation trends and change points of runoff and sediment flowing into and out of Hongze Lake during the period 1975–2015. It is concluded that the annual variation trend of the inflow and outflow runoff time series is consistent, with no obvious decreasing trend and change point, while the inflow and outflow sediment time series showed a decreasing trend, and the change point was 1991. Then, the runoff and sediment time series were analyzed by the wavelet method. The results showed that the time series has multi-time scale characteristics. The annual inflow runoff and sediment would enter into the dry period in a short time after 2015, and both would be in the valley floor stage. Among the influencing factors, the variation of rainfall in the basin was the main factor affecting the runoff variation. Changes in heavy rainfalls pattern, the construction of hydraulic engineering projects, and land use/cover change (LUCC) are the main reasons for the significant decrease and mutation variation of inflow sediment.

Development of a real-time forecasting model for turbidity current arrival time to improve reservoir desilting operation

ABSTRACTAmong various strategies for sediment reduction, venting turbidity currents through dam outlets can be an efficient way to reduce suspended sediment deposition. The accuracy of turbidity current arrival time forecasts is crucial for the operation of reservoir desiltation. A turbidity current arrival time (TCAT) model is proposed. A multi-objective genetic algorithm (MOGA), a support vector machine (SVM) and a two-stage forecasting technique are integrated to obtain more effective long lead-time forecasts of inflow discharge and inflow sediment concentration. The multi-objective genetic algorithm (MOGA) is applied for determining the optimal inputs of the forecasting model, support vector machine (SVM). The two-stage forecasting technique is implemented by adding the forecasted values to candidate inputs for improving the long lead-time forecasting. Then, the turbidity current arrival time from the inflow boundary to the reservoir outlet is calculated. To demonstrate the effectiveness of the TCAT model, it is applied to Shihmen Reservoir in northern Taiwan. The results confirm that the TCAT model forecasts are in good agreement with the observed data. The proposed TCAT model can provide useful information for reservoir sedimentation management during desilting operations.

Investigation of an oceanic plateau formation and rifting initiation model implied by the Caroline Ridge on the Caroline Plate, western Pacific

ABSTRACT The rifting of oceanic plateaus is an important mechanism for initiating lithospheric break-up and subsequent seafloor spreading. In this study, we present the latest multichannel seismic data investigating the Caroline Ridge and provide one of the typical cases for initial oceanic plateau evolution. We reveal that a smooth basement reflector (R2), as the top of the lava flows, is subparallel to the sediments with horizontal seismic reflections over the surface of the Caroline Ridge. Thick layer-parallel lava flows beneath the R2 appear within the crust. Large seamounts in the Sorol Trough possess abundant saucer-shaped intracrustal reflectors, and the overlying sediments were destroyed by intrusive bodies. The overlying sedimentary sequences, basement, and thick lava flows on the Caroline Ridge flanks were faulted by opposing normal fault sets, and the eruptions of the seamounts deformed the strata. A widespread bright horizontal reflector (R1), as an unconformity inside the Caroline Ridge sediments, truncates the lower tilted sediment layers and is itself cut by normal faults in the flank strata. Furthermore, we propose that subaerial lava flows extended laterally from the hotspot magmatism localizing in the Sorol Trough and led to Caroline Ridge formation. The initial rifting of the Caroline Ridge occurred during the Early-Middle Miocene. Limited volcanoes concentrate only in the Sorol Trough due to the attenuated thermal effect. It is suggested that dome uplifting and far-field force could have jointly caused initial rifting process of the Caroline Ridge.

FLOOD FLOW AND BED VARIATION ANALYSIS METHOD FOR GRAVEL BED RIVER OF THE KAMANASHI RIVER WITH LARGE AMOUNT OF INFLOW SEDIMENT DURING LARGE-SCALE FLOOD

FLOOD FLOW AND BED VARIATION ANALYSIS METHOD FOR GRAVEL BED RIVER OF THE KAMANASHI RIVER WITH LARGE AMOUNT OF INFLOW SEDIMENT DURING LARGE-SCALE FLOOD

Eastern oyster clearance and respiration rates in response to acute and chronic exposure to suspended sediment loads

Coastal Louisiana supports some of the most productive areas for the eastern oyster, Crassostrea virginica. Changing conditions from restoration and climate change alter freshwater and sediment inflows into critical estuarine areas affecting water quality, including salinity and concentrations of suspended sediment. This study examined the effects of acute (1 h) and chronic (8 weeks) exposure of suspended sediment concentrations on the eastern oyster's respiration and clearance rates. Acute exposure at six sediment concentrations (0, 10, 50, 200, 500, 1000 mg L−1) and one salinity (15) indicated that sediment concentration significantly affected oyster clearance rates, with increasing clearance rates as suspended sediment concentrations increased up to 500 mg L−1. Respiration rates were not affected by sediment concentration (p = .12). Chronic exposure at two salinities (6 and 15) and three sediment concentrations (0, 50, 400 mg L−1) found no significant effect of sediment, salinity or their interaction on clearance rates. Respiration rate was reduced at higher sediment concentrations (50 and 400 mg L−1 versus 0 mg L−1) and lower salinity. As clearance and oxygen consumption rates critically inform oyster energetic models, these data provide valuable insight to more accurately predict eastern oyster population dynamics and inform harvest models in the face of changing estuarine conditions. Changes in rates of growth through altered energetic demands ultimately can impact not just the economic viability of the industry, but also the ability for the populations to maintain sustainable reefs.

Innovative design solutions to ensure the environmental safety in the existing water intake technological complexes of water systems for urban farms

The main design flaws in terms of protection against young fish entering the water intake bucket, sediment inflows, sludge and floating objects, which largely do not provide the current regulatory environmental requirements for ensuring environmental safety (ES) of water intake technological complexes (WITC) directly interacting with the natural water environment (WE) of the water body (MPWS) as a part of the natural technical system (NTS) “WE-WITC-MPWS” were identified during the comprehensive studies to assess the functional effectiveness of existing water intake structures (about 44) of multi-purpose water supply systems (“MPWS.”) of urban farms and settlements in the Lower course of the river Don from the Tsimlyansky reservoir to the mouth (Azov).In order to ensure the operating “WITC” operating systems based on the results of constructive studies using domestic experience in the use of high-strength synthetic fabric materials, an innovative design of a water intake structure in the form of a soft floating structure (SFS) has been developed providing the regulatory requirements on the main indicators of ES by 85%-95%.

Evolution Trend of the Changjiang (Yangtze) Estuary with reduced incoming sediment

The reduction of fluvial sediment input has brought new features to the evolution of the Changjiang (Yangtze) Estuary. The response of river channels and shoals in the Changjiang Estuary are still unclear. A two-dimensional model of water and sediment transport in the Changjiang Estuary is established by using MIKE21. The sediment gradation and the flocculation of the fine sediment have been considered in the model. After calibration, the future evolution trend of the Changjiang Estuary was simulated based on the measured terrain in November 2016. The inflow of water and sediment at Jiangyin from 2008 to 2017 were taken as the upstream inlet conditions. The simulation results show that the pattern of river channel and shoals in the Changjiang Estuary will basically remain, and the main trend of bed evolution is erosion in deep channel and siltation of shoals.

Characterization of Deltaic Channel Morphodynamics From Imagery Time Series Using the Channelized Response Variance

River deltas are complex, dynamic systems whose channel networks evolve in response to internal and external forcings. To capture these changes, methods to extract and analyze deltaic morphodynamics automatically using available remotely sensed imagery and experimental observations are needed. Here, we apply a promising method for the automatic extraction of channel presence called RivaMap, on both synthetic and experimental data sets, to investigate the changes experienced by the system in response to five changes in forcings. RivaMap is an automated method to extract nonbinarized channel locations from imagery based on a singularity index that combines the multiscale first and second derivatives of the image intensity to favor the identification of curvilinear features and suppress edges. We quantify how the channelization varies by computing the channelized response variance (CRV), which we define as the variance of each pixel's singularity index response through time. We find that increasing magnitudes of sediment inflow (Qs) and water inflow (Qw) result in corresponding increases in the maximum CRV. We find that increasing the ratio of Qs to Qw results in increased number of channelized areas. We see that adding cohesion to the exposed sediment surface of the experimental delta results in decreased magnitude and decreased number of channelized areas in the CRV. Finally, by observing changes to the CRV over time, we are able to quantify the timescale of internal channel reorganization events as the experimental delta evolves under constant forcings.

Temporal and spatial variation of infiltration in urban green infrastructure

AbstractInfiltration is the primary mechanism in green stormwater infrastructure (GSI) systems to reduce the runoff volume from urbanized areas. Soil hydraulic conductivity is most important in influencing GSI infiltration rates. Saturated hydraulic conductivity (Ksat) is a critical parameter for GSI design and post‐construction performance. However, Ksat measurement in the field is problematic due to temporal and spatial variability and measurement errors. This review paper focuses on a comparison of methods for in‐situ Ksat measurement and the causes of temporal and spatial variations of Ksat within GSI systems. Automated infiltration testing methods, such as the Modified Philip–Dunne (MPD) and SATURO infiltrometers, show promise for efficient Ksat measurements. Soil Ksat values can change over time and substantially vary throughout a GSI, which can be attributed to multiple factors, including but not limited to temperature changes, soil composition and properties, soil compaction level, plant root morphology and distribution, biological and macrofauna activities in the soil, inflow sediment characteristics, quality of infiltrating water, and measurement errors. There is evidence that infiltration rates in vegetated urban GSI systems are sustained given an appropriate GSI design, reasonable concentration of suspended sediments in the inflow runoff, and routine maintenance procedures. These observations indicate that clogging can be counteracted by processes that tend to increase the soil hydraulic conductivity (e.g., plant root and biological activities). This self‐sustainability underlines that infiltration‐based GSI systems are a reliable long‐term stormwater management solution. Recommendations on how to incorporate the temporal changes of Ksat in GSI design and on obtaining a spatially‐representative Ksat for the GSI design are presented.