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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Unit Hydrograph Estimation for Applicable Texas Watersheds</title>
      <link>https://trid.trb.org/View/2572969</link>
      <description><![CDATA[The unit hydrograph is defined as a direct runoff hydrograph resulting from a unit pulse of excess rainfall generated uniformly over the watershed at a constant rate for an effective duration. The unit hydrograph method is a well-known hydrologic-engineering technique for estimation of the runoff hydrograph given an excess rainfall hyetograph. Four separate approaches are used to extract unit hydrographs from the database on a per watershed basis. A large database of more than 1,600 storms with both rainfall and runoff data for 93 watersheds in Texas is used for four unit hydrograph investigation approaches. One approach is based on 1-minute Rayleigh distribution hydrographs; the other three approaches are based on 5-minute gamma-distribution hydrographs. The unit hydrographs by watershed from the approaches are represented by shape and time to peak parameters. Weighted least-squares regression equations to estimate the two unit hydrograph parameters for ungauged watersheds are provided on the basis of the watershed characteristics of main channel length, dimensionless main channel slope, and a binary watershed development classification. The range of watershed area is approximately 0.32 to 167 square miles. The range of main channel length is approximately 1.2 to 49 miles. The range of dimensionless main channel slope is approximately 0.002 to 0.020. The equations provide a framework by which hydrologic engineers can estimate shape and time to peak of the unit hydrograph, and hence the associated peak discharge. Assessment of equation applicability and uncertainty for a given watershed also is provided. The authors explicitly do not identify a preferable approach and hence equations for unit hydrograph estimation. Each equation is associated with a specific analytical approach. Each approach represents the optimal unit hydrograph solution on the basis of the details of approach implementation including unit hydrograph model, unit hydrograph duration, objective functions, loss model assumptions, and other factors.]]></description>
      <pubDate>Mon, 29 Sep 2025 11:14:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/2572969</guid>
    </item>
    <item>
      <title>Literature Review on Timing Parameters for Hydrographs</title>
      <link>https://trid.trb.org/View/2571791</link>
      <description><![CDATA[This report summarizes the literature review for the Texas Department of Transportation (TxDOT) project 0-4696 "Estimating Timing Parameters of Direct Runoff and Unit Hydrograph for Texas Watersheds.” Chapter 1 summarizes background information of the NRCS (Natural Resources Conservation Service) dimensionless unit hydrograph, which TxDOT is currently using for its hydrologic design and includes general information about streamflow hydrographs and unit hydrograph. Chapter 2 summarizes various common definitions for the timing parameter of direct runoff and unit hydrograph. Chapter 3 summarizes methods to quantify timing parameters: (1) NRCS velocity method, (2) particle tracking method, and (3) empirical equations developed from earlier studies for several common timing parameters. Chapter 4 summarizes definitions for watershed parameters because many empirical equations are based on correlation between timing parameters and watershed parameters. Chapter 5 summarizes conclusions made based upon literature review findings.]]></description>
      <pubDate>Tue, 02 Sep 2025 10:34:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/2571791</guid>
    </item>
    <item>
      <title>Effects of Regulation on L-Moments of Annual Peak Streamflow in Texas</title>
      <link>https://trid.trb.org/View/2570753</link>
      <description><![CDATA[Several techniques exist to estimate annual peak-streamflow frequency for streamflows that have recurrence intervals ranging from 2 to 500 years for natural (unregulated) drainage basins in Texas. Unfortunately, such techniques have limited applicability in regulated basins. There are numerous regulated basins throughout Texas, which has more than 7,000 dams that are identified by Texas Natural Resource Conservation Commission permits. The effects on annual peak streamflow from reservoirs created by these dams range from negligible to the complete suppression of the flood hydrograph; also, reservoirs can artificially create flood-like hydrographs. The large number of reservoirs and their widespread distribution in Texas necessitate an assessment of flood characteristics in regulated basins. Therefore, the U.S. Geological Survey, in cooperation with the Texas Department of Transportation, conducted a study of the effects of regulation on L-moments of annual peak streamflow in Texas. For this report, the State was divided into three regions. Four regression equations to estimate the L-moments of natural annual peak-streamflow data for ungaged sites were derived for each region from data for 367 streamflow-gaging stations in natural basins. The explanatory variables in the equations are contributing drainage area, basin shape factor, and stream slope. The effects of regulation on the L-moments of annual peak-streamflow data were determined by analysis of maximum and normal storage-capacity data from reservoirs for 96 streamflow-gaging stations in variously regulated basins. The results indicate that as potential flood storage (defined by the difference between total maximum and normal capacity) in a basin increases, the mean annual peak streamflow decreases nonlinearly. Evidence strongly indicates (despite contrary expectation) that the higher L-moments (coefficient of L-variation, L-skew, and L-kurtosis) are unaffected by regulation.]]></description>
      <pubDate>Sat, 30 Aug 2025 16:09:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/2570753</guid>
    </item>
    <item>
      <title>An Initial-Abstraction, Constant-Loss Model for Unit Hydrograph Modeling for Applicable Watersheds in Texas</title>
      <link>https://trid.trb.org/View/2570792</link>
      <description><![CDATA[Estimation of representative hydrographs from design storms, which are known as design hydrographs, provides for cost-effective, risk-mitigated design of drainage structures such as bridges, culverts, roadways, and other infrastructure. During 2001–07, the U.S. Geological Survey (USGS), in cooperation with the Texas Department of Transportation, investigated runoff hydrographs, design storms, unit hydrographs, and watershed-loss models to enhance design hydrograph estimation in Texas. Design hydrographs ideally should mimic the general volume, peak, and shape of observed runoff hydrographs. Design hydrographs commonly are estimated in part by unit hydrographs. A unit hydrograph is defined as the runoff hydrograph that results from a unit pulse of excess rainfall uniformly distributed over the watershed at a constant rate for a specific duration. A time-distributed, watershed-loss model is required for modeling by unit hydrographs. This report develops a specific time-distributed, watershed-loss model known as an initial-abstraction, constant-loss model. For this watershed-loss model, a watershed is conceptualized to have the capacity to store or abstract an absolute depth of rainfall at and near the beginning of a storm. Depths of total rainfall less than this initial abstraction do not produce runoff. The watershed also is conceptualized to have the capacity to remove rainfall at a constant rate (loss) after the initial abstraction is satisfied. Additional rainfall inputs after the initial abstraction is satisfied contribute to runoff if the rainfall rate (intensity) is larger than the constant loss. The initial-abstraction, constant-loss model thus is a two-parameter model. The initial-abstraction, constant-loss model is investigated through detailed computational and statistical analysis of observed rainfall and runoff data for 92 USGS streamflow-gaging stations (watersheds) in Texas with contributing drainage areas from 0.26 to 166 square miles. The analysis is limited to a previously described, watershed-specific, gamma distribution model of the unit hydrograph. In particular, the initial-abstraction, constant-loss model is tuned to the gamma distribution model of the unit hydrograph. A complex computational analysis of observed rainfall and runoff for the 92 watersheds was done to determine, by storm, optimal values of initial abstraction and constant loss. Optimal parameter values for a given storm were defined as those values that produced a modeled runoff hydrograph with volume equal to the observed runoff hydrograph and also minimized the residual sum of squares of the two hydrographs. Subsequently, the means of the optimal parameters were computed on a watershed-specific basis. These means for each watershed are considered the most representative, are tabulated, and are used in further statistical analyses. Statistical analyses of watershed-specific, initial abstraction and constant loss include documentation of the distribution of each parameter using the generalized lambda distribution. The analyses show that watershed development has substantial influence on initial abstraction and limited influence on constant loss. The means and medians of the 92 watershed-specific parameters are tabulated with respect to watershed development; although they have considerable uncertainty, these parameters can be used for parameter prediction for ungaged watersheds. The statistical analyses of watershed-specific, initial abstraction and constant loss also include development of predictive procedures for estimation of each parameter for ungaged watersheds. Both regression equations and regression trees for estimation of initial abstraction and constant loss are provided. The watershed characteristics included in the regression analyses are (1) main-channel length, (2) a binary factor representing watershed development, (3) a binary factor representing watersheds with an abundance of rocky and thin-soiled terrain, and (4) curve number. Physical interpretations of the regression coefficients are made. Finally, an evaluation of an initial-abstraction, constant-loss model for general application is made through four techniques of parameter estimation: the mean and median watershed-specific values, regression equations, and regression trees. The results show that the four techniques have similar overall performance, but measurable differences exist. The four techniques, when combined, are shown to provide unbiased estimates of peak streamflow and reliably represent runoff volumes as well as times of peak streamflow occurrence with less uncertainty than any single technique. The combined initial-abstraction, constant-loss model used with the gamma distribution model of the unit hydrograph is suggested for general application in Texas, and discussion in the context of practical applications is provided.]]></description>
      <pubDate>Sat, 23 Aug 2025 18:22:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2570792</guid>
    </item>
    <item>
      <title>Measurement and Simulation of Flow on Surfaces with Extreme Low Slope for Determination of Time of Concentration</title>
      <link>https://trid.trb.org/View/2571780</link>
      <description><![CDATA[Field laboratory experiments and numerical simulations were used to explore the question of estimating time of concentration for regions with negligible slope. Current methods for estimating time of concentration generally have the slope of the land surface in the denominator of the functional relationship. This means that as slope decreases to zero, the time of concentration becomes infinite, which is contrary to observations. Researchers performed a set of experiments with a rainfall simulator over beds of very low slope. The resulting hydrographs were used to determine the time of concentration as a function of the slope and other pertinent variables. A numerical model was also developed to simulate the flow of water over a low-slope surface with random microtopography. While the field measurements provided some successful insight, the results from the two approaches were not able to determine definitively a relationship for time of concentration that can be used in all cases. The field laboratory study may have suffered from being too small scale compared to the area of the watersheds (~100 Ac) for which time of concentration is sought. The numerical study suffered from instabilities brought about by the nature of the equations modeled and, possibly, from lack of knowledge about the boundary conditions. Based on the experience and knowledge gained from this work, it is recommended that future work to determine the time of concentration for regions of low slope would benefit from one or more field observation facilities, where rainfall and flow records could be measured. Additionally, because different times of concentrations were derived in this study depending on the flow conditions or time of concentration determination technique, a standard definition (or standard definitions) of time of concentration is needed.]]></description>
      <pubDate>Sat, 23 Aug 2025 18:22:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2571780</guid>
    </item>
    <item>
      <title>Predicting urban stormwater flooding using geomorphic information</title>
      <link>https://trid.trb.org/View/2485390</link>
      <description><![CDATA[Stormwater flooding has emerged as a major challenge in urban areas due to its widespread and adverse impacts on transportation and the normal functioning of the economy. It can also cause loss of life. To predict the depth and duration of flooding at a specific locale, one could use the tools developed for river flooding (due to backwater). These include accurately mapping the terrain and running hydrologic software such as SWMM or HEC-HMS followed by hydraulic engineering software such as HEC-RAS. However, due to the high number of flooding locations, such a task is cost prohibitive. 

For this reason, the research team proposes to develop empirical correlations that could predict the discharge and the depth of sheet flow and their durations based on easily measurable quantities, such as upslope, downslope, area, land-use, etc.. To obtain these correlations, the team will select twenty archetypical sites in the City of Newark along with standard design storms to conduct the standard hydrologic modeling approach followed by hydraulic engineering calculations. The team will then correlate various aspects of the hydrographs and water depths with the geomorphic factors stated above. The team believes that such an approach, if successful, would allow rapid evaluation of flooding in Newark and other similar cities, such as New York City, and will thus allow contingency planning and appropriate allocation of transit resources. 
]]></description>
      <pubDate>Sun, 05 Jan 2025 15:51:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2485390</guid>
    </item>
    <item>
      <title>Forecasting Hurricane Storm Surge on the Mississippi River</title>
      <link>https://trid.trb.org/View/2228400</link>
      <description><![CDATA[The National Weather Service (NWS) is responsible for forecasting stages for the major rivers in the United States. The Lower Mississippi River Forecast Center (LMRFC) is responsible for forecasting river stages on the Mississippi River below Chester, IL, on the Ohio River below Smithland Lock and Dam, IL, and continuing from the confluence of the Ohio-Mississippi to the Gulf of Mexico. The LMRFC prepares and issues daily forecasts for twenty-one locations along the mainstems of the lower Ohio and Mississippi Rivers. A unique forecast problem is the forecasting of stages on the lower Mississippi River when a hurricane induced storm surge is present. Storm surge waves move rapidly upstream and can cause significant damage and delays to barge traffic along the Mississippi River. The LMRFC has combined the NWS Dynamic Wave Operational Model (DWOPER), a one-dimensional unsteady state flow model, on the Mississippi River with output from the Sea, Lake, and Overland Surge Heights (SLOSH) model. The SLOSH model generates a storm surge hydrograph on the Mississippi River at a pre-selected grid point near West Pointe a la Hache, LA. This hydrograph is used as a downstream boundary in DWOPER to produce stage forecasts as a hurricane storm surge travels upstream on the Mississippi River.]]></description>
      <pubDate>Sun, 20 Oct 2024 15:54:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2228400</guid>
    </item>
    <item>
      <title>Highway Hydrology Third Edition</title>
      <link>https://trid.trb.org/View/2401895</link>
      <description><![CDATA[This manual discusses the physical processes of the hydrologic cycle that are important to highway engineers. These processes include the approaches, methods, and assumptions applied in design and analysis of highway drainage structures. Hydrologic methods of primary interest are frequency analysis for analyzing rainfall and flow data; empirical methods for peak flow estimation; and hydrograph analysis and synthesis. The manual describes the concept and several approaches for determining time of concentration and rainfall-runoff processes. It also provides information on hydrologic data sources and selecting tools for a given application. The peak flow methods discussed include log-Pearson type III, regression equations, and the Rational Method. The technical discussion of each peak flow approach also includes urban development applications. The manual includes development of design hydrographs and design storms. The manual presents common storage and channel routing techniques related to highway drainage hydrologic analyses and includes information on hydrologic modeling, uncertainty, and risk in hydrologic analysis applications. Special topics in hydrology include discussions of wetlands hydrology and mitigation design, snowmelt hydrology, and arid lands hydrology.]]></description>
      <pubDate>Mon, 15 Jul 2024 09:05:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2401895</guid>
    </item>
    <item>
      <title>Experimental Investigation of Time-Dependent Clear Water Scour around Bridge Pier Due to a Trapezoidal Hydrograph</title>
      <link>https://trid.trb.org/View/2280190</link>
      <description><![CDATA[Local scours around bridge piers influence their stabilities and play a key role in bridge failures. In this study, the local scours around a bridge pier resulting from unsteady flow are investigated. The experiments are carried out in a rectangular flume 80 cm wide and 18.6 m long by using uniform sediment with median diameter of 3.5 mm and geometric standard deviation of 1.4. The unsteady flow is generated by means of a trapezoidal hydrograph. The bridge pier with circular cross section has a diameter of 8 cm. The flow depth is monitored by ultrasonic sensors and the flow rate is measured by electromagnetic flow meter. The temporal variations of scour depth are measured indirectly, by placing Ultrasonic Velocity Profiler (UVP) transducers downward vertically. Three transducers of 4 MHz are located around the bridge pier. The local scours due to input hydrograph are obtained by registering the distances from the tip of the transducer to the top level of the sediment layer in the course of unsteady flow experiments. The temporal evolution of local scours as well as the final depths and configurations of the local scours are obtained. The experimental findings are interpreted in the light of present classical knowledge. This study constitutes the first part of the researches planned to investigate the time dependent local scours due to various trapezoidal hydrographs.]]></description>
      <pubDate>Wed, 27 Dec 2023 15:03:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2280190</guid>
    </item>
    <item>
      <title>Developing Customized NRCS Unit Hydrographs (Finley UHs) for Ungauged Watersheds in Indiana</title>
      <link>https://trid.trb.org/View/2222586</link>
      <description><![CDATA[The Natural Resources Conservation Service (NRCS, formerly the Soil Conservation Service, SCS) unit hydrograph (UH) is one of the most commonly used synthetic UH methods for hydrologic modeling and engineering design all over the world. However, previous studies have shown that the application of the NRCS UH method for some ungauged watersheds in the state of Indiana produced unrealistic flood predictions for both the peak discharge and the time to peak. The objective of this work is to customize the NRCS UH by analyzing the role of its two key parameters, namely, the peak rate factor (PRF) and the lag time, in creating the runoff hydrograph. Based on 120 rainfall-runoff events collected from 30 small watersheds in Indiana over the past two decades, the observed UHs are derived and the corresponding PRF and lag time are extracted. The observed UHs in Indiana show that the mean value of PRF is 371, which is lower than the standard PRF of 484, and the NRCS lag time equation tends to underestimate the “true” lag time. Moreover, a multiple linear regression method, especially the stepwise selection technique, is employed to relate the NRCS UH parameters to the most appropriate geomorphic attributes extracted from the study watersheds. Both the statewide and regional regression models show that the main channel slope is a major factor in determining the PRF and lag time. A customized Indiana unit hydrograph, referred as Finley UH to honor David Finley who inspired this study, is derived with updated parameters and the Gamma function. Validation results show that the Finley UH provides more reliable and accurate predictions in terms of the peak discharge and the time to peak than the original NRCS UH for the watersheds in Indiana.]]></description>
      <pubDate>Wed, 09 Aug 2023 13:23:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2222586</guid>
    </item>
    <item>
      <title>Analysis of the hydraulic performance of permeable pavements on a layer-by-layer basis</title>
      <link>https://trid.trb.org/View/2170753</link>
      <description><![CDATA[Permeable pavement systems are a sustainable urban drainage technique created with a highly porous base and subbase. This study first analyses the hydraulic performance of several new permeable pavement systems based on 189 experimental hydrographs. In addition, the analysis explores the influence of rain intensity, slope, and, as a novelty, individual layers. Analysed variables were outflow peak, time to peak, and time to specific cumulative discharges. Secondly, based on the experimental hydrographs, the study explores the performance of the permeable pavement module defined in the Storm Water Management Model, carried out in two steps. First, single-layer outflows were used to calibrate parameter values that could not be measured physically, using the differential evolution algorithm and Nash–Sutcliffe model efficiency coefficient as an objective function. Later, complete layout hydrographs were tested without calibration, and model performance was checked. Results show that the superficial permeable interlocking paver layer provides a notably higher retention capacity than the porous asphalt mixture. Individual modelling results show that the soil layer definition is inappropriate for gravel-type layers, even with a geotextile. Despite this, complete section performance is quite good without calibration if the soil layer is not selected on the model. These results are expected to reduce modelling uncertainty, especially when no calibration data is available.]]></description>
      <pubDate>Wed, 28 Jun 2023 16:29:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2170753</guid>
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    <item>
      <title>Evaluating Nonlinear Methods to Generate Flood Hydrographs for Bridge Scour Applications</title>
      <link>https://trid.trb.org/View/2100813</link>
      <description><![CDATA[Bridge scour evaluations are often performed using streamflow estimates from regional regression relationships. This approach relies on the accuracy of the relationships and does not consider the effects of flow variations. Alternatively, a complete hydrograph can be obtained from a watershed model and used in the scour analysis. However, hydrograph estimation is complicated by nonlinearities in basin response, particularly when large storm events are considered. The objective of this study was to determine whether nonlinearities in hydrologic response and the relationship between flow rates and scour can substantially impact bridge scour evaluations. Nonlinearity in the relationship between excess precipitation and direct runoff was included using variable Clark unit hydrograph parameters in a Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) model. Flow depths and velocities were then generated using a two-dimensional Hydrologic Engineering Center - River Analysis System (HEC-RAS) model. Both models were developed for the Cheyenne Creek watershed west of Colorado Springs. Anticipated scour was quantified using approaches detailed in the Federal Highway Administration’s Hydraulic Engineering Circular manuals. Regression-based peak flow estimates applied as steady state discharges produced larger scour depths than unsteady hydrographs obtained from the hydrologic models. The hydrographs simulated using the variable Clark unit hydrograph parameters produced substantially larger scour depths than those simulated using constant Clark unit hydrograph parameters.]]></description>
      <pubDate>Tue, 24 Jan 2023 09:27:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2100813</guid>
    </item>
    <item>
      <title>Research on Dimensionless Unit Hydrograph and Time of Concentration for Maryland Watersheds</title>
      <link>https://trid.trb.org/View/2072569</link>
      <description><![CDATA[Observed data from 100 rainfall-runoff events on 54 watersheds in Maryland and Delaware were used to investigate two watershed characteristics: the dimensionless unit hydrograph (DUH) and time of concentration (Tc). Streamflow hydrograph data were obtained from US Geological Survey gaging stations. Event hyetographs were generated from US Weather Service NEXRAD Radar Stage III data (DPR) using a method developed in this study. The gamma-function form of the Natural Resources Conservation Service unit hydrograph was assumed. For each event, an optimization method was used to determine the time to peak and gamma parameter (related to the Peak Rate Factor, PRF) that give the best-fit direct runoff hydrograph when convolved with the rainfall excess hyetograph. Tc was estimated by differentiation of the unit hydrograph. Efforts to predict PRF and Tc using watershed properties, and to update an existing regression equation, were inconclusive. Future investigations will focus on improving the event baseflow separation and determination of rainfall excess.]]></description>
      <pubDate>Tue, 20 Dec 2022 09:12:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2072569</guid>
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    <item>
      <title>Flood Hydrograph Generation for Predicting Bridge Scour in Cohesive Soils</title>
      <link>https://trid.trb.org/View/1998979</link>
      <description><![CDATA[Three bridge sites in South Dakota with streamflow records ranging from 50 to 67 years were selected to compute the histories of pier or contraction scour using the Scour Rates In COhesive Soils (SRICOS) method. Scour depths were computed using a range of soil erosion functions representative of cohesive and non-cohesive soils. The results show that a continuous hydrograph spanning several decades may be replaced by a series of maximum annual floods. A tiered approach for using the SRICOS method was developed. In the Level I analysis, the results of soil classification or soil erosion rate testing are used with simple calculations to eliminate bridge sites where use of the SRICOS method is not recommended. In the Level II analysis, recorded hydrographs are used to predict the final scour depths produced by floods of different return periods to assess scouring potential. In the Level III analysis, annual maximum series are generated and used with the SRICOS method to compute the exceedance probabilities associated with different scour depths and project lives. Each flood in the annual maximum series has a constant discharge sampled randomly from the Log Pearson Type III (LP-III) distribution and an equivalent duration computed using a regression equation.]]></description>
      <pubDate>Fri, 29 Jul 2022 09:17:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/1998979</guid>
    </item>
    <item>
      <title>Sources and Impacts of Uncertainty in Uncalibrated Bioretention Models Using SWMM 5.1.012</title>
      <link>https://trid.trb.org/View/1845162</link>
      <description><![CDATA[Using the USEPA’s Storm Water Management Model version 5.1.012 (SWMM), a case study of a street right-of-way bioretention system (ROWB) configured as a storage node is compared against SWMM’s Low Impact Development (LID) Controls for urban runoff retention, detention, and the timing of discharge. Through 12,000 one-year continuous simulations, single parameter perturbations and Monte-Carlo simulation of the uncalibrated models result in predicted annual runoff coefficients (representing stormwater retention) of 0.19–0.55 for an exfiltrating ROWB compared to 0.61 and 0.72 for a storage node with low and high assumed exfiltration capacity, respectively. Stormwater detention was represented by the frequency of event peak discharges exceeding an arbitrary low threshold value. The storage node simulations predicted peak discharges near or exceeding the upper values for the LID Control simulations. The dynamic representation of flow through porous media in the LID Control predicts greater retention and detention compared to the storage node over the range of uncalibrated models investigated. Sensitivity analysis of the LID Control parameterization indicates that the relative difference between the engineered media’s porosity and field capacity have the most significant influence on predicted performance. Poor runoff retention results in scenarios where the engineered media exhibits a high field capacity relative to its porosity, whereas high field capacity is a desirable trait that should lead to superior performance. The model’s calculation procedures and neglect of unsaturated flow or preferential pathways bias model output toward more frequent runoff bypass. The sensitivity analysis also demonstrates that the timing and duration of the discharge hydrograph are highly variable depending on parameterization. The wide range of potential performance generated from uncalibrated model parameterization leads to significant concerns for infrastructure planning and implementation, leading potentially to underperforming infrastructure, or excessive cost. Allocating resources to collect field performance data that enables robust model development, calibration, and verification at the green infrastructure (GI) stormwater control measure (SCM) scale offers the opportunity to reduce uncertainty in model predictions.]]></description>
      <pubDate>Mon, 19 Apr 2021 17:20:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/1845162</guid>
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