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The design of the Lower White River Countyline Setback Project in Washington State includes lowering an existing levee and constructing a new setback levee to allow the river to reconnect to an existing wetland. This study used two hydrodynamic and sediment transport models, Hydrologic Engineering Center-River Analysis System (HEC-RAS), and Adaptiv...
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... design proposes a new setback levee and removes a significant portion of an existing levee to allow the river to reconnect with 121 acres of wetland occupying a former relict river channel. Figure 3 shows a simplified representaion of the project's design. This site was previously included in the Puyallup River General Investigations (GI) Study that used 1D HEC-RAS models for a basin-wide sediment transport analysis of the Puyallup watershed 1 ( Gibson et al. 2017). ...
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... other area refers mostly to the right overbank. Figure 30 shows the sedimentation broken down by grain size for the existing conditions run. ...
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... changes are shown in Figure 33 and Figure 34 for the existing and proposed conditions, respectively. Both models resulted in aggradation in both the main channel and the setback area, but the amount of deposition increased significantly in the proposed scenario. ...
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... changes are shown in Figure 33 and Figure 34 for the existing and proposed conditions, respectively. Both models resulted in aggradation in both the main channel and the setback area, but the amount of deposition increased significantly in the proposed scenario. ...
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... higher incoming flows also meant more incoming sediment, resulting in more in-channel deposition. Figure 35 and Figure 36 show the aggradation and degradation that occurred during the 2-year period, respectively. The proposed levee setback model had a total deposition of 143,000 cy, with 47,000 cy occurring in the main channel. ...
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... higher incoming flows also meant more incoming sediment, resulting in more in-channel deposition. Figure 35 and Figure 36 show the aggradation and degradation that occurred during the 2-year period, respectively. The proposed levee setback model had a total deposition of 143,000 cy, with 47,000 cy occurring in the main channel. ...
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... results in less deposition in areas downstream of the return flow. Figure 37 shows the aggradation for the proposed conditions. The areas with the highest aggradation are all located near where the levee lowering occurred. ...
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... main levee cut at the beginning of the setback area shows the most deposition. Degradation is shown in Figure 38. The cross sections below ( Figure 39 and Figure 40) were extracted from the AdH mesh for both the existing and proposed conditions models in the same location as the HEC-RAS cross sections shown in Figure 33 and Figure 34, respectively. ...
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... is shown in Figure 38. The cross sections below ( Figure 39 and Figure 40) were extracted from the AdH mesh for both the existing and proposed conditions models in the same location as the HEC-RAS cross sections shown in Figure 33 and Figure 34, respectively. Both the with and without project conditions show the bottom of the main channel aggrading along with some deposition in the left overbank area. ...
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... is shown in Figure 38. The cross sections below ( Figure 39 and Figure 40) were extracted from the AdH mesh for both the existing and proposed conditions models in the same location as the HEC-RAS cross sections shown in Figure 33 and Figure 34, respectively. Both the with and without project conditions show the bottom of the main channel aggrading along with some deposition in the left overbank area. ...
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... is shown in Figure 38. The cross sections below ( Figure 39 and Figure 40) were extracted from the AdH mesh for both the existing and proposed conditions models in the same location as the HEC-RAS cross sections shown in Figure 33 and Figure 34, respectively. Both the with and without project conditions show the bottom of the main channel aggrading along with some deposition in the left overbank area. ...
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... model results show that large amounts of sediment could deposit in the cut initially and then more deposition could occur every time flow overtops the notch, building back a natural levee. A plan view and profile view of the deposition at the levee notch are shown in Figure 42 and Figure 43, respectively. Velocities for the first high flow (6,100 cfs) that causes most of the initial deposition in the notch are shown in Figure 44. ...
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This document presents a levee setback case study on the Sangamon River near Beardstown, IL. Five potential setback scenarios were tested using a Hydrologic Engineering Center-River Analysis System (HEC-RAS) hydraulic and sediment model. HEC-RAS results demonstrated differences in flood reduction and sediment trapping opportunities among gate openi...
Citations
... Because of the investments by King County in repeat monitoring, post-project elevation change data are available to assist with model calibration. Consistent with the predictions of the previous AdH modeling work by Jones et al. (2018) sedimentation has been focused in the vicinity of the upstream connection between the mainstem and the restored site. ...
... This modeling was comprehensively updated in the late-2000's (Czuba et al. 2010) by the USGS who re-surveyed the reach and incorporated sediment transport data from previous studies. This work was followed by project specific updates by the Corps (Gibson et al. 2017) which led to a detailed one-dimensional (1D) and two-dimensional (2D) sediment transport model investigation (Jones et al. 2018) of the large-scale King County designed and constructed Countyline levee setback project (King County, 2020). ...
... In 2015 the Coastal and Hydraulics Laboratory at ERDC began a series of investigations to document setback levee projects (Smith et al. 2017) that led to modeling of the proposed Countyline setback project using the Corps 1-dimensional (1D) HEC-RAS and 2-dimanesional (2D) Adaptive Hydraulics (AdH) numerical modeling software (Jones et al. 2018). Gibson et al. 2017). ...
This paper is focused on summarizing recent sediment models developed by the U.S Army Corps of Engineers (USACE/Corps) to better understand the dynamic, coarse-bedded alluvial fan formed by the Lower White River in Washington State. The paper illustrates practical uses of the Adaptive Hydraulics (AdH) and 1D and 2D HEC-RAS sediment transport models to look at issues related to channel capacity and setback levee design. The modeling is focused on hindcasting observed changes resulting from the recently constructed Countyline levee setback project. All models performed reasonably well at matching depositional trends. The 2D AdH and 2D HEC-RAS exhibited highly dynamic behavior consistent with observed changes namely channel establishment, bar building, braiding, and channel abandonment relevant for feature design (levee breach configuration, macro scale roughness elements). The AdH model had the greatest fidelity to observed changes but required one week on a supercomputer to simulate 4 years. The HEC-RAS 2D model was practical to set up on a desktop PC but struggled with long run times and had a harder time reproducing smaller scale changes in the floodplain and channel. The branching 1D model was able to reproduce reach scale trends in the main channel and reconnected floodplain and was used to efficiently forecast near-term (5-year) changes in channel capacity relevant for emergency management. Both 1D and 2D models should be considered for dynamic reaches-with 1D models used to quickly analyze reach scale phenomena and to constrain and inform 2D models that are focused on understanding complex changes in shorter time horizons/spatial domains. While all models show immense promise for more reliably managing flood risks in dynamic rivers, further improvements in hardware and software are needed before these types of investigations become routine. This talk is a companion to the Comport et al. paper.
... Given recent advancements in available morphodynamic modeling tools (Jones et al. 2018), it should be possible to improve the standard of practice and confidence in restoration outcomes through more detailed numerical modeling of sediment entrainment, transport, and deposition, even in settings that have typically not been ideal. The challenges of modeling coarse-bedded rivers are well known (Wilcock et al. 2009, Parker 2008) and are often due to a lack of bed-load data for calibration (Bunte 2004). ...
The US Army Corps of Engineers, Seattle District, nourishes gravel downstream of Howard Hanson Dam (HHD) on the Green River in Washington State. The study team developed numerical models to support the ongoing salmonid habitat improvement mission downstream of HHD. Recent advancements in computing and numerical modeling software make long-term simulations in steep, gravel, cobble, and boulder river environments cost effective. The team calibrated mobile-bed, sediment-transport models for the pre-dam and post-dam periods. The modeling explored geomorphic responses to flow and sediment regime changes associated with HHD construction and operation. The team found that pre-dam conditions were significantly more dynamic than post-dam conditions and may have had lower spawning habitat quality in the project vicinity. The team applied the Bank Stability and Toe Erosion Model to the site and then calibrated to the post-dam gravel augmentation period. The team implemented a new hiding routine in HEC-RAS that improved the simulated grain size trends but underestimated coarse sediment transport. Models without the hiding function overestimated grain size but matched bed elevations and mass flux very well. Decade-long simulations of four future gravel nourishment conditions showed continued sediment storage in the reach. The storage rate was sensitive to nourishment mass and grain size.
... Hydraulic models, such as the Hydrologic Engineering Center-River Analysis System (HEC-RAS) or Adaptive Hydraulics (AdH) can provide useful information about how levee setbacks may alter the flow of water and sediment in a river (Theiling et al. 2018;Jones et al. 2018). These models, however, do not provide information about how the ecosystem will change due to a levee setback and the associated change in nutrient dynamics. ...
Levee setbacks are defined by the intentional relocation of levees away from the river bank. This placement is often done to reduce flood risk, but it can also have environmental benefits. The Comprehensive Aquatic System Model (CASM) was used to look at the potential fate of nutrients and several environmental benefits for five potential management scenarios along the lower Sangamon River in Illinois. The model results showed that two scenarios were much more environmentally favorable relative to the outcomes considered here. One of the scenarios, where the existing gates were operated to allow the river access to the area behind the levee during extreme floods, was better at nitrogen and phosphorous accumulation. Removing the gates and creating a levee setback at this same site produced more aquatic plants, invertebrates, and fish but was not as effective at nutrient accumulation. This application of CASM demonstrates the potential of the model to provide objective rankings for the environmental benefits of levee setbacks.
... The HEC-RAS (Hydrologic Engineering Center-River Analysis System) software is a free hydraulic simulation modelling software released by the US Army Corps of Engineering [4,5]. The simulation shows the behaviour of the Cibeureum River, the water level, and the velocity in both steady and unsteady conditions [6]. ...
Cilember River flows from North to South of Cimahi and crosses PURBALEUNYI Toll Road in downstream. Therefore normalization of Cilember River Cimahi can impact the PURBALEUNYI Toll road. Hydraulic simulation carried out to determine the impact and formulate the mitigations alternatives. The study was conducted based on Detail Engineering Design Data for Cilember Normalisation Program prepared by Citarum River Authority as a base data. Two-dimensional HEC-RAS model was used to simulate the impact of the river normalization program. The model also used to evaluate the alternatives (detention pond, diversion of flows) to minimize the impact of the Cilember normalization program to PURBALEUNYI Toll road. Applying 10 year return period and HEC-RAS simulation, with an existing condition, 26 505 sqm area is inundated mostly in the North area of Toll Roads. After the normalization program, the inundation area shifts to the south area, including Toll road. The further simulation shows that normalization of the river can reduce inundation area to 7 993 sqm. Simulation of combination between detention pond and diverting the excess flow of Cilember to Kali Malang inundated area occurs, but it does not affect the toll road.
... While studies are beginning to examine the similarities and differences between these models [3], the specific complex nature of local conditions will require a large number of case studies to begin to completely understand situations where one approach is superior to the other given data and budget constraints and multiple project goals. There have been numerous studies concluding that 2D models are superior or at least equal to 1D models which, given unlimited budgets for data collection, calibration, and sufficient modeling expertise, would seem rather obvious [4]- [6]. However, as concluded by Gibson and Pasternack [7], the most important questions revolve around how much better and at what additional cost? ...
... The USACE Seattle District modeled proposed levee setback projects using a one-dimensional (1D) model and estimated significant rates of sedimentation in the setback areas. The U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory (ERDC-CHL), researchers revisited this site using a two-dimensional model and predicted much lower sedimentation rates in the reconnected floodplain ( Jones et al. 2018). A related research effort at ERDC-CHL established design and performance expectations for several typical levee setback designs in an effort to apply model heuristics to the USACE SMART 1 planning process (USACE 2012) (i.e., to show expected levee setback responses for rapid alternative screening) (Echevarria-Doyle and Dahl 2018). ...
This document presents a levee setback case study on the Sangamon River near Beardstown, IL. Five potential setback scenarios were tested using a Hydrologic Engineering Center-River Analysis System (HEC-RAS) hydraulic and sediment model. HEC-RAS results demonstrated differences in flood reduction and sediment trapping opportunities among gate opening and levee-removal scenarios. Levee removal upstream of a bridge and causeway provided the greatest sediment reduction potential. Increasing flow into connected floodplain areas offered intermediate flood and sediment reduction benefits but did not improve natural resource benefits. Levee removal and land conversion provided the greatest natural resources benefit, but substantial economic loss. This study demonstrates the potential benefits of levee setbacks across the U.S. Army Corps of Engineers navigation, ecosystem restoration, and flood management mission areas.
