Joanna Crowe Curran

Linking bed morphology changes of two sediment mixtures to sediment transport predictions in unsteady flows

Flume experiments were conducted to measure bed morphology adjustments in sand/gravel and sand/silt sediment mixtures during repeated hydrographs and to link these changes to sediment transport patterns over multiple time scales. Sediment composition and hydrograph flow magnitude greatly influenced channel morphology, which impacted sediment yield, hysteresis, and transport predictions. Bed load yields were larger and more variable for the sand/silt mixture, as gravel in the sand/gravel sediment inhibited grain entrainment, limited bed form growth, and acted to stabilize the bed. Hysteresis patterns varied due to bed form and surface structure adjustments, as well as the stabilizing effect of antecedent low flows. Using half the data set, a dimensionless fractional transport equation was derived based on excess shear stress. Dimensionless reference shear stresses were estimated in two ways: as bulk values from all transport measurements and by applying a separate limb approach in which values were estimated for each limb of each hydrograph. For the other half of the data set, transport predictions with the separate limb approach were more accurate than those from six existing transport equations and the fractional relationship applied with bulk reference shear stresses. Thus, hydrograph limb-dependent dimensionless reference shear stress links changing bed morphology and sediment transport, providing a parameter to improve transport predictions during individual flood events and in unsteady flow regimes. This approach represents a framework with which to develop site-specific transport relationships for varying flow regimes, particularly in cases where detailed bed morphology measurements are not feasible and heterogeneous sediment complicates bed structure over time.

The importance of bed sediment sand content for the structure of a static armor layer in a gravel bed river

The surface structure of static armor layers generated from water-worked gravel bed channels was investigated with primary focus on the influence of sand content and flow rate. Flume experiments were conducted in which four sediment mixtures with sand contents between 1% and 38% were armored under one of three different flow rates. First- and second-order statistical analyses were applied to digital elevation models of unarmored, armored, and clustered bed surface areas to identify changes in surface structure. Results were combined with data from previous research to create an extended data set of armored bed surfaces. Water-worked, unarmored bed surfaces established under a dynamic equilibrium flow rate impacted the topographic variability and structure of the armored beds. Surface complexity decreased with armor formation as surface grains preferentially aligned with the flow direction. The bed surface became smoother, and where sediment mixture sand content was constant, there was greater smoothing of the surface during higher armoring flows as grains rearranged more easily. As bulk sand content increased, statistical analyses of the expanded data set showed that beds with very little sand content developed static armor layers that remained rough and had greater topographic variability than armor layers from sediments with higher sand contents. The bulk sediment sand content exerted a stronger influence over the change in surface roughness and structure upon armoring than that of the flow rate during armor formation. When combined with the knowledge of the local flow regime, the sand content may aid in predictions related to armored bed surface structure.

Comparison of Turbulent Flows over Clusters of Varying Density

AbstractGravel bed rivers commonly form an armored surface layer within which cluster bedforms develop. Clusters can form in isolation or develop cluster groups of increasing density. Flume experiments are presented in which a clustered, armored surface was formed on a gravel bed. Flows were measured over an area without a cluster and areas with an isolated cluster, a coupling of two clusters, and a group of three clusters. Turbulent flow parameters, Reynolds stresses, and turbulent kinetic energy were calculated from acoustic Doppler velocimeter measured flows and visualizations of the flow patterns around clusters. Flow separated over the cluster crest, creating an increase in the turbulent flow properties and a high-turbulence intensity region when flow reattached downstream. Turbulent kinetic energy increased around the coupled clusters, but around the grouped clusters, the flow field was distinguished by a high degree of uniformity. The net effect of increasing density of cluster grouping was an incr...

Importance of Hydrology on Channel Evolution Following Dam Removal: Case Study and Conceptual Model

AbstractA slow draining reservoir on the U.S. East Coast was monitored to identify the processes governing channel evolution upstream of a dam removal. Channel evolution was documented through cross section surveys, sediment size analysis, discharge measurements, and visual assessments of vegetative growth. The reservoir drained slowly, allowing for an analysis of channel evolution and identification of the morphometric parameters defining the path and time required for a channel to reach dynamic equilibrium. Channel evolution was a multidirectional process, and evolving channel reaches actively migrated laterally while alternating between aggradation and degradation. Channel formation was dominated primarily by the hydrologic regime at the time of dam removal and secondarily by the ability of vegetation to establish and stabilize the channel form. The importance of seasonal site hydrology over the minimum time required for channel evolution and the process through which the channel evolves indicates the ...

Effect of Bed Sand Content on the Turbulent Flows Associated with Clusters on an Armored Gravel Bed Surface

AbstractAs a gravel bed river armors, a bed surface often develops clusters as part of its structure. The influence of sand on armoring and the impact of clusters on the surrounding flow processes were investigated through flume experiments. Armored beds were created from four different sediments, which progressively increased from 1–38% sand in the bed sediment, extending from gravel framework to sand matrix beds. Turbulent kinetic energy (TKE) and xz-direction Reynolds stress calculated from velocity profiles showed the clusters increased turbulence and induced formation of recirculation cells. Similar recirculation cells formed downstream of every cluster, but the strength and orientation of these cells varied with bed condition. The increase in sediment sand content and change in bed condition from gravel framework to sand matrix correlated to an increase in the energy and momentum in the recirculation cell but a reduction in cluster influence across the flow profile. Results show that the sand conten...

Imaging VCAM-1 as an Indicator of Treatment Efficacy in Metastatic Ovarian Cancer

The inability to successfully treat women with ovarian cancer is due in large part to the advanced stage of disease at diagnosis, the development of platinum resistance, and the lack of sensitive methods to monitor tumor progression and response to treatment. Vascular cell adhesion molecule-1 (VCAM-1) is expressed on the mesothelium of ovarian cancer patients. We investigated VCAM-1 expression as a marker of peritoneal metastasis and tumor response to platinum-based chemotherapy. Methods: Peritoneal or omental biopsies obtained from women diagnosed with stage I, stage II, or stage III/IV ovarian cancer were evaluated by immunohistochemistry. The effects of carboplatin on mesothelial VCAM-1 expression were determined in cultured cells by Western blot. Radiolabeled VCAM-1–specific peptide imaging probes and SPECT were used in a mouse model of ovarian cancer peritoneal metastasis to identify VCAM-1 as a viable imaging target. Results: VCAM-1 expression correlated with tumor stage. All specimens from stage I patients were negative, whereas 29% of stage II patients and 73% of stage III/IV patients were positive. Although most women with advanced stage disease expressed VCAM-1, the incidence of expression was reduced among women who received neoadjuvant chemotherapy, suggesting a role for chemotherapy in regulating VCAM-1 expression. Treatment of mesothelial cells in culture with carboplatin resulted in a transient decrease in VCAM-1 expression 4 h after treatment that returned to baseline within 16–24 h. In vivo imaging of VCAM-1 also demonstrated an acute decrease in expression 4 h after carboplatin administration that recovered within 48 h in mice harboring platinum-resistant tumors. Chronic VCAM-1 expression reflected the effect of platinum-based treatment on tumor burden. Specifically, carboplatin treatment of mice with platinum-sensitive tumors showed reduced VCAM-1 expression, which correlated with reduced tumor burden; mice with platinum-resistant tumors retained elevated VCAM-1 expression and tumor burden after treatment. Conclusion: Clinically relevant VCAM-1–specific imaging probes identify VCAM-1 expression as an indicator of ovarian cancer peritoneal metastasis and therapeutic response to platinum-based agents. These observations support testing the utility of VCAM-1 imaging probes to monitor treatment response in ovarian cancer patients, thus providing the potential to improve management of women with this disease.

Reply to comment by Luis A. Giménez‐Curto and Miguel A. Corniero Lera on “Characteristic dimensions of the step‐pool bed configuration: An experimental study”

[1] The dominant dimension of the step-pool bed form is its spacing, which is determined by the locations at which large, step-forming grains are deposited. We conducted laboratory experiments involving active transport of widely sorted sediment, including large grains whose deposition readily formed steps. Direct observation of step development indicates that deposition of step-forming grains was predominantly associated with bed roughness impeding transport or with earlier flow and transport conditions not contemporaneous with step development. Neither mechanism is likely to occur at regular locations on the bed. Measured step spacing was found to follow a Poisson distribution, supporting the conclusion that steps do not develop in preferred or regular locations. This contrasts with previous arguments that regular step spacing develops in response to deposition forced at regular locations beneath water surface waves. We observe neither the regular distribution nor the associated depositional mechanism, although the observed step distribution is well defined with a strong mode that could be interpreted as indicating regular spacing.

A Comparison of Modeled Flood Characteristics to Measurements of the 2002 Flood on the Guadalupe River, Texas

There are a number of equations and models for calculating flood probabilities and associated peak discharges, and this paper compares a model and an empirical calculation. We calculated flood characteristics for the upper Guadalupe watershed in central Texas using the Weibull formula and data available from a local gauging station, to the result given by the National Flood Frequency (NFF) program, developed by the U.S. Geological Survey (USGS). During the summer of 2002, the upper Guadalupe watershed received a total of 89 cm (35 in.) of precipitation over a one-week period, producing record flooding. The results from both the NFF program and the calculation of return intervals using gauging station data are compared to the measured peak flows for the summer of 2002. The peak discharges predicted by both the NFF model and from the USGS gauging station data are much higher than the recorded discharge. There may be an increase of flow inputs to the Guadalupe River between the locations of the gauging station and where the flood estimate was made. Assuming an increase from tributaries into Canyon Lake, the estimate of peak discharge obtained from USGS data much more closely matches the recorded flow than the results from the NFF program.

Effects of an emergent vegetation patch on channel reach bathymetry and stability during repeated unsteady flows

While research into the interaction between in-channel vegetation, flow, and bed sediment has increased in recent years, there is still a need to understand how unsteady flows affect these processes, particularly in terms of channel bed adjustments. In this study, flume experiments tested two flood hydrograph sizes run over sand/gravel and sand/silt beds to evaluate reach scale impacts of a mid-channel vegetation patch of variable stem density on channel bathymetry and stability. Alternating flood hydrographs with periods of low, steady flow created flow sequences reflective of an extended unsteady flow regime, thereby simulating time scales consisting of multiple flood events. Digital elevation models provided detailed measurements of channel change following each flood event to enable analysis over each unsteady flow sequence. The vegetation patch created characteristic channel bathymetries dependent on sediment mixture and patch density that in all cases resulted in a more variable bed structure than channels without a patch. Reach scale stability, quantified based on net volumetric bed change, only occurred with a sparse patch in the low flood sequence, corresponding with little variation in surface composition and structure. In most other cases, scour measured at the patch prevented stability at the reach scale, especially in the finer substrate. Overall, findings show that a channel may only adjust to a stable bathymetry upon addition of a mid-channel vegetation patch within a limited range of flow regimes and patch stem densities, and that for the experimental conditions tested here, in-stream patches generally did not enhance reach scale bed stability. This article is protected by copyright. All rights reserved.

Abstract A62: Imaging the tumor micro-environment to monitor ovarian cancer metastasis

The inability to successfully treat women with ovarian cancer is due in large part to the advanced stage of disease at diagnosis, the development of platinum resistance, and the lack of sensitive methods to monitor tumor progression and response to treatment. Vascular cell adhesion molecule-1 (VCAM-1) is expressed on the mesothelium of ovarian cancer patients. We investigated VCAM-1 expression as a marker of peritoneal metastasis and tumor response to platinum-based chemotherapy. Immunohistochemical staining of peritoneal or omental biopsies obtained from women diagnosed with Stage I, Stage II or Stage III/IV ovarian cancer demonstrated that VCAM-1 expression correlated with tumor stage. All specimens from Stage I patients were negative, while 29% of Stage II patients and the 73% of Stage III/IV patients were positive. While the majority of women with advanced stage disease expressed VCAM-1, the incidence of expression was reduced among women who received neoadjuvant chemotherapy, suggesting a role for chemotherapy in regulating VCAM-1 expression. The effects of carboplatin on mesothelial VCAM-1 expression were determined in a mouse model of ovarian cancer peritoneal metastasis using radiolabeled VCAM-1-specific peptide imaging probes and single photon emission computed tomography (SPECT). This approach showed that 1) VCAM-1 is a viable imaging target in ovarian cancer metastasis, 2) maximal expression was detected with microscopic tumor burden, and 3) VCAM-1 expression reflected the effect of platinum-based treatment on tumor burden. Specifically, carboplatin treatment of mice with platinum-sensitive tumors showed reduced VCAM-1 expression, which correlated with reduced tumor burden; mice with platinum-resistant tumors retained elevated VCAM-1 expression and tumor burden following treatment. These observations support testing the utility of VCAM-1 imaging probes to monitor treatment response in ovarian cancer patients, thus providing the potential to improve management of women with this disease. Citation Format: Jill K. Slack-Davis, Jennifer M. Scalici, Stephanie Thomas, Christine Harrer, Timothy A. Raines, Joanna Curran, Kristen A. Atkins, Mark R. Conaway, Linda Duska, Kimberly A. Kelly. Imaging the tumor micro-environment to monitor ovarian cancer metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A62.