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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>Research in Progress (RIP)</title>
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      <link>https://rip.trb.org/</link>
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    <item>
      <title>Hydrologic and Hydraulic Software Enhancements 2 (SMS, WMS, Hydraulic Toolbox, and HY-8)</title>
      <link>https://rip.trb.org/View/2640674</link>
      <description><![CDATA[This Transportation Pooled Fund (TPF) project will: 1) Enhance the capabilities of the four Federal Highway Administration (FHWA) sponsored software programs and ensure they remain consistent with the latest FHWA technical reference documents; 2) Update the software user manual documentation; 3) Make new software versions publicly available; 4) Develop and deploy technology transfer materials and workshops to test and demonstrate new software content and features; 5) Inform users of the availability of new software versions and features through website postings, email notifications, newsletter articles, conference presentations, and other avenues.]]></description>
      <pubDate>Wed, 17 Dec 2025 15:42:55 GMT</pubDate>
      <guid>https://rip.trb.org/View/2640674</guid>
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    <item>
      <title>Synthesis of Information Related to Highway Practices. Topic 57-02. Rational Method for Hydrology Upper Area Thresholds and Hierarchy of Use
</title>
      <link>https://rip.trb.org/View/2630483</link>
      <description><![CDATA[State departments of transportation (DOTs) must accurately estimate stormwater drainage to design infrastructure that minimizes risks such as roadway flooding, overtopping and embankment failures. A range of hydrologic methods are available, and method selection influences infrastructure performance and safety.  For small watersheds draining to highway rights-of-way, the Rational Method remains widely used due to its simplicity and long-standing application.

There is no uniform agreement on the maximum drainage area for which the Rational Method is appropriate. Federal and state guidance, academic literature, and engineering texts present differing limits, leading to inconsistent application. The method’s underlying assumptions also diminish in validity as watershed size and complexity increase, and many state DOTs do not specify when more advanced hydrologic methods should be applied.  Complexities may include the presence of tributaries, nonuniform and longer duration rainfall, soil and land use variability, and storage within the watershed. 

OBJECTIVE: The objective of this synthesis is to document state DOT policies, practices, and guidance in the application of the Rational Method for hydrologic analysis of watersheds.]]></description>
      <pubDate>Wed, 26 Nov 2025 17:54:27 GMT</pubDate>
      <guid>https://rip.trb.org/View/2630483</guid>
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    <item>
      <title>Development of a Roadway Flood Severity Index</title>
      <link>https://rip.trb.org/View/1869811</link>
      <description><![CDATA[This study develops a retrospective Roadway Flood Severity Index (RFSI) capable of integrating geo-located hydrometeorological data and roadway information across localized and multi-state, sub-national regions in order to (1) categorize larger-scale, flood-related transportation disruptions, (2) understand the origins of those disruptions, and (3) identify severity risk levels of individual road segments and broader regions of transportation disruption during flood events. The fundamental question is, as flooding events unfold, can past hydrometeorological inundation information be coupled with transportation system network and mobility data to identify the most vulnerable roadway segments and regions? To address this question, the following tasks are in progress: (1) An ex-post facto analysis of historical flood events and the disruptions that they caused to multi-state, sub-national transportation mobility, focusing on how distinct flood types impact the road network and if any other compounding characteristics (e.g., regional variations, types of flooding, road-specific information) can be identified; (2) A mathematical, machine-learning based RFSI to highlight road segment flood risk for two multi-state regions; and (3) Development of a minimally-viable visualization tool to disseminate RFSI outputs with an emphasis on promotion of data interoperability.]]></description>
      <pubDate>Sat, 31 Jul 2021 22:29:33 GMT</pubDate>
      <guid>https://rip.trb.org/View/1869811</guid>
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      <title>Predicting Roadway Washout Locations During Extreme Rainfall Events</title>
      <link>https://rip.trb.org/View/1765389</link>
      <description><![CDATA[Recent extreme rainfall events have revealed the transportation network’s vulnerabilities to road washouts. Currently, North Carolina Department of Transportation (NCDOT) reacts to these problems as are reported from the field. This inability to predict where washouts are likely to occur leads to long response times and inefficient positioning of resources. The availability of high quality statewide elevation data, historical rainfall records and advances in computer processing presents the opportunity to modify and develop programs to predict where washouts are likely to occur during extreme rainfall events. The purpose of this project is to develop models and test several approaches for predicting crossing washouts based on forecasted rainfall. A team of North Carolina State University Department of Biological and Agricultural Engineering (NCSU BAE) engineers will first characterize and analyze historical washouts during extreme events. Then, detailed Hydrologic Engineering Center-hydrologic modeling system (HEC-HMS) models will be developed and calibrated and validated for one watershed in each physiographic region. A user interface will be created to run the models using forecasted rainfall, relate the predicted discharge to potential washouts using water surface elevation-discharge relationships, and then output the results for display in a geographic information systems (GIS) map. The model output for a large number of historical events will then be used to test different machine learning algorithms for their ability to predict discharge and potential washout locations. The information on historical washouts and the model predictions will be used to develop a network of “safe” routes for each watershed. The results will help determine if existing hydrologic models can be leveraged to accurately predict potential washout locations and to evaluate if machine learning technology can be employed for accurate flood prediction. This project has the potential to substantially enhance NCDOT’s ability to respond to storm events and position resources appropriately. Results will be disseminated in NCDOT meetings, a training workshop for NCDOT personnel, and through extension factsheets and academic publications.]]></description>
      <pubDate>Tue, 26 Jan 2021 08:03:32 GMT</pubDate>
      <guid>https://rip.trb.org/View/1765389</guid>
    </item>
    <item>
      <title>Watershed Approach to Mitigating Hydrologic Impacts of Transportation Projects</title>
      <link>https://rip.trb.org/View/1516189</link>
      <description><![CDATA[State departments of transportation (DOTs) are facing increasingly stringent requirements for treating not only the quality but also the quantity of stormwater runoff. State DOTs are required to address project-related hydrologic volume impacts under the Endangered Species Act (ESA) and the Clean Water Act, and in some cases, state and local regulations. For example, in Oregon, ESA Biological Opinions for highway projects require maintaining pre-project hydrology for channel-forming flows; in King County, Washington, projects must reestablish pre-development hydrology. 
Increased quantity of stormwater runoff can be a result of increased impervious surfaces and other land use changes, stream channelization, soil compaction, or changes to the precipitation regime (frequency and intensity of storms). These changes alter the storm hydrograph with increased runoff volumes, heightened peak flows, and shortened durations of the runoff event. Hence, hydrologic impacts can increase flooding, trigger and accelerate stream channel change, increase sediment loads and turbidity, alter groundwater recharge, harm aquatic habitat, and reduce low-flow discharges. 
There are a number of effective techniques for mitigating hydrologic change. For example, the impacts of increased impervious surface area can be mitigated by techniques such as reconnecting floodplains; reforestation; or conserving, constructing, or restoring wetlands. These techniques can reduce, delay, and desynchronize peak flows. These techniques also offer important co-benefits, such as providing recreational opportunities and fish and wildlife habitat. However, to be most effective, techniques for addressing runoff volumes require a watershed-based strategy that combines specific techniques into an overall plan for managing the hydrologic impacts from transportation facilities. 
Research is needed to develop a fuller array of effective strategies and techniques for managing increased stormwater runoff volumes and mitigating hydrologic impacts associated with transportation projects. As regulatory requirements increasingly address stormwater runoff quantity, state DOTs need information on a range of techniques that can support effective watershed-based strategies. The research and resulting guidance will support the efforts of engineers, environmental staff, and planners at state DOTs and their regulatory and other partners with flexible approaches to regulatory compliance and improved environmental outcomes. 
The objective of this research is to develop guidance for state DOTs for developing and implementing watershed-based strategies and techniques for mitigating hydrologic impacts of transportation facilities. The results of the research will be guidance on how to:  
(1) Identify opportunities in a watershed to conserve, restore, enhance, or create landscape features for hydrologic mitigation; 
(2) Plan, site, and design features for hydrologic mitigation; 
(3) Quantify the hydrologic outcomes from selected features; and 
(4) Develop strategies for implementing a watershed-based approach to hydrologic mitigation. ]]></description>
      <pubDate>Tue, 19 Jun 2018 13:08:16 GMT</pubDate>
      <guid>https://rip.trb.org/View/1516189</guid>
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