Base Level Engineering is a watershed-wide engineering modeling method that leverages high resolution ground elevation, automated model building techniques, and manual model review to prepare broad and accurate flood risk information for FEMA to assess its current flood hazard inventory. Base Level Engineering prepares flood risk information with scalable engineering, allowing FEMA to both assess its current flood hazard inventory and expand the coverage and availability of flood risk information to communities and individuals interested in reviewing their potential flood risk.

Goal: Centralized and available flood hazard analysis to support floodplain management activities and development review, while increasing risk awareness for individuals.

The InFRM Flood Decision Support Toolbox (FDST) is an interactive web application which:

• visualizes current flood-related weather conditions in FEMA region 6 (Arkansas, Louisiana, New Mexico, Oklahoma, Texas),
• allows peace-time analysis by emergency planners, local governments, and other stakeholders preparing for potential response activities (such as planned evacuation routes, identification of vulnerable areas requiring road closure, and resource planning in advance of flood events),
• leverages federal, state, regional and local engineering model information to develop pre-positioned flood inundation libraries for micro-level efforts (neighborhood level),
• connects National Water Model predictions for macro-level planning (community, county, state level),
• uses pre-positioned map libraries to illustrate areas of potential flood inundation areas in relation to a field reported streamgage height,
• can be expanded by data submittals by other Federal/State agencies, river management authorities, and other stakeholders, and
• will be limited to the extent and availability of streamgage locations across the region.

As hydrology remains the single largest source of uncertainty in our understanding of flood risk, the InFRM team has been performing Watershed Hydrology Assessments (WHAs) to update flood risk estimates in large, complex river basins using suites of models developed by USACE.

The InFRM WHAs are performed by an expert team of engineers and scientists from multiple federal agencies using the latest advances in hydrologic science and technology. WHAs examine the hydrology across the entire basin, reviewing non-stationary influences, such as regulation, land use changes, and climate variation, to ensure all variables affecting flood risk in the watersheds are considered. The multi-layered analysis of the WHAs employs a range of hydrologic methods, including rainfall runoff modeling, statistical hydrology, period-of-record simulations, and reservoir analyses, and then compares the results of those methods to previous studies and to one another.

The goal of the WHAs is to produce consistent 1% annual chance (100-yr) and other frequency flows across the river basin, based on all available hydrologic information. The final recommendations of the WHAs are formulated through a rigorous review process which includes technical investigations, external peer reviews, stakeholder input, and collaboration between all of the InFRM subject matter experts.

Watershed Hydrology Assessment Basins

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River basins within the region are selected for hydrology assessments based on watersheds where USACE already has sufficiently detailed modeling products available as a starting point for the assessments and where FEMA had future floodplain mapping activities scheduled.

InFRM WHAs have been completed for the following river basins in FEMA Region 6:

• the Guadalupe River Basin in Texas,
• the Trinity River Basin in Texas,
• the Neches River Basin in Texas,
• the Little River Basin in Oklahoma,
• the Lower Colorado River Basin in Texas,
• the Nueces River Basin in Texas, and
• the White River Basin in Arkansas.

The final reports and appendices for these studies can be downloaded from the PRODUCTS section.

InFRM WHAs are currently underway for the following river basins:

• the Brazos River Basin in Texas.

Additional basins will be added to the program as funding allows.

As a result of the level of investment, analyses, and collaboration that go into the WHAs, their results are recommended as the best available estimate of flood risk for the studied streams in the river basin, and they provide suggestions for areas where the current flood hazard information may need to be updated. The results from the WHAs can also be used to plan new infrastructure and safely locate new neighborhoods and other urban development. Furthermore, the models and data used to produce these flood risk estimates are available upon request, at no charge, to communities, local stakeholders, and architecture engineering firms.

For more information from any of these studies, please contact us.