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Davis, CA, United States

Scharffenberg W.A.,Hydrologic Engineering Center | Kavvas M.L.,University of California at Davis
Journal of Hydrologic Engineering

Flood wave routing is a common problem in water resources engineering, for example, when a hydrograph enters a stream channel and passes downstream to an observation station. In the past, the problem has been approached by making the best possible estimate of the inflow hydrograph. The channel properties such as geometry and roughness are also estimated, along with any lateral inflow. The best estimates are used with a flood wave routing model to predict the hydrograph at the downstream observation station. Making a prediction by this procedure is full of challenges. It is impossible to exactly know the precise form of the hydrograph that will enter the channel. It is also difficult to select the channel properties from the range of values that may be appropriate. Lateral inflow is notoriously difficult to quantify. Making predictions under these circumstances is full of uncertainties. One approach to analyzing uncertainties is to use Monte Carlo modeling to make quantitative estimates of the uncertainty in flood wave routing results. The best estimates used for boundary conditions and model parameters are replaced by probability estimates. The ensemble of results from the Monte Carlo framework can be analyzed to develop probabilistic estimates of the routed hydrograph at the outlet of the channel reach. While this is a powerful approach, it also requires extensive probability data for the boundary conditions and channel properties. Such input data are rare in the published literature and do not appear to exist at all for lateral-inflow-dominated streams. This study examines the flood wave routing problem in a probabilistic framework using the kinematic wave model. It develops a complete data set for a lateral-inflow-dominated stream that includes a probabilistic description of the inflow hydrograph and lateral inflow. It also includes probability density functions for the parameters used in the kinematic wave model. The resulting data set appears to be the first developed for a lateral-inflow-dominated stream, though data sets do exist for streams without significant lateral inflows. Beyond the development of a new data set, this study seeks to evaluate the relative contributions of uncertainty in boundary conditions and channel parameters to the total uncertainty in the routed flood wave. Results for the lateral-inflow-dominated case developed here are compared to a similar example where lateral inflow is not significant. The results found here suggest that in both cases it is the uncertainty in boundary conditions that is most significant and dominates the total uncertainty in the routed flood wave. © 2011 ASCE. Source

Gibson S.,Hydrologic Engineering Center | Heath R.,Engineer Research and Development Center | Abraham D.,Engineer Research and Development Center | Schoellhamer D.,University of California at Davis
Water Resources Research

Sand infiltration into gravel frameworks affects a wide range of ecological, geomorphic, and engineering processes. Four flume experiments were conducted with tracer materials to examine how a sand pulse infiltrates into a gravel bed. These experiments were primarily designed to test two hypotheses: (1) that vertical gradational trends of interstitial deposits are due to differential transport of finer sand in suspended load (hydraulic sorting) and (2) that the formation of a bridge layer (a thin layer of infiltrated sediments that become lodged in shallow pore throats) precludes subsequent infiltration into a gravel framework. Several sand colors were sequentially introduced into a flume containing a gravel substrate. After the experiments were conducted bed cores were collected and separated into vertical layers including surface layers composed primarily of sand that was transporting as bed load before the experiment was terminated and interstitial deposits in the gravel framework. Sand from each layer was sieved and measured. The color distribution of each grain class of each vertical layer of each core was measured to determine the temporal provenance of the interstitial deposits. Results supported the occurrence of hydraulic sorting. Older (finer) sand particles were disproportionately prevalent in interstitial deposits when compared to bed load samples. The experiments did not support the second hypothesis. Substantial secondary infiltration occurred after the initial formation of a bridge layer. More secondary infiltration was measured for systems with higher d 15Gravel/d 85Sand ratios and when bed shear was sufficient to mobilize the gravel. Copyright 2011 by the American Geophysical Union. Source

Hu H.,WEST Consultants Inc. | Giovando J.,Hydrologic Engineering Center | Cahill R.,Hydrologic Engineering Center | Klipsch J.,Hydrologic Engineering Center | And 3 more authors.
International Journal on Hydropower and Dams

The overall goal of the Columbia River Treaty 2014/2024 (CRT) Review is to meet the responsibility of the US Entity, which is to provide the accountable parties with information necessary to support a US decision regarding the future of the Treaty. The US Entity comprises the US Army Corps of Engineers (USACE) and Bonneville Power Administration (BPA). The CRT Review has included analyses of the two current Treaty purposes, flood risk management and hydropower. This paper reviews the process used in generating regulated streamflows for the CRT Review flood risk analysis. Source

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