Eulerian-Lagrangian-agent Method / Evaluating Likely Animal Movement (ELAM)

Published Oct. 29, 2014
Comparison of fish "agent" with real fish

Comparison of fish "agent" with real fish

A Psychophysical Approach to Engineering Design for Animal Movement

The Eulerian‐Lagrangian‐agent Method (ELAM) is an approach developed by ERDC’s Environmental Laboratory for analyzing and forecasting the movement and distribution patterns of individual animals responding to environmental conditions on land and in the water.  Using environmental information available from GIS and other engineering (e.g., hydrodynamic, water quality) models or those conditions measured a priori from field data, the ELAM approach allows biologists, engineers, scientists and managers to explore observed animal movement patterns in a way that provides:

  • A mechanistic biological explanation (hypothesis) of observed movement patterns that can be further studied (e.g., validated) with experimental means.
  • A systematic, tractable means for forecasting the movement behavior response of a population, composed of individuals, to alternative land and water resource management strategies.

An Indispensible Tool for Conservation Managers

To conserve threatened and endangered (T&E) species that navigate fragmented landscapes and rivers, management typically tries to repel individuals from dangerous areas and/or attract individuals to areas of safety.  The behavior of individual animals has generally been difficult to manipulate, however.  Psychophysics offers an approach for relating environmental stimuli that an animal perceives into a form and function that can be used to analyze, reproduce, and sometimes forecast response to management action.  An ELAM first represents the environment as a computational mesh (Eulerian component), such as a grid or mesh from geographic information system (GIS) or hydrodynamic modeling.  Numerical particles are then simulated (Lagrangian component) in the domain with behaviors (agent component) representing responses to variables stored in the mesh.  A key element in the ELAM approach is describing how the animal's perception of its surroundings varies with context and time.  Animals evaluate the world in relative terms and behavior can change based simply on the temporal pattern of an incoming stimulus.  Psychophysical concepts are important to developing tools and strategies needed to progress conservation efforts.  The ELAM approach allows managers to evaluate how multiple external and internal factors interact to mediate behavioral choice that at times may appear irrational.

Success Stories

An ELAM model was recently used to reproduce a decade of Pacific salmon observations navigating dams; previously, these observations had eluded explanation.  The unique success of this work and its impact on how civil infrastructure worldwide may be better managed led to publication of the findings in one of the world’s leading science journals, Proceedings of the National Academy of Sciences:



  • Lower Granite Dam, where the ELAM model flagged a proposed field evaluation as unlikely to succeed in eliciting the needed animal (fish) response.  While the ELAM model output was viewed skeptically at first, as managers dug into “why” the model was generating a forecast of unexpected outcomes, they soon agreed with the model’s output and significantly modified the engineering design before field evaluation.  The ELAM model saved many millions of dollars — compared to “build and test” — by flagging a design that was unlikely to meet needed objectives that otherwise would have taken a full year to discover.  The ELAM model accomplished this by showing beforehand the outcome of animal behavior that can be hard to envision.
  • Rocky Reach Dam, where the ELAM model was used by the private sector to understand the reasons that an engineering design was not performing as desired in eliciting a response from a specific species of migrating fish
  • Priest Rapids Dam, where the ELAM model was used by the private sector to select the best design for construction among many dozens of alternative options
  • Wanapum Dam, where the ELAM model was used by the private sector to select the best design for construction among many alternative options
  • Richard B. Russell Dam, where the ELAM model was used to understand why fish would be injured under specific dam operations
  • Sacramento River Flood Control Project, where the ELAM model is being used to understand behavior response to fish-friendly habitat features on levees
  • Chicago District Asian Carp Project, where the ELAM model is being used to understand carp response to an electrical barrier


  • Arizona, where the ELAM model is being used to improve the management of this species in concert with Air Force training


  • Indiana


  • Georgia

Cost, Distribution

Cost varies.  Use of the model is available within the U.S. government through interagency agreement.  For entities outside the U.S. government, use of the model is available through a cooperative research and development agreement.

Documentation, Training & Support

Below is a link to several videos that illustrate ELAM model output:

Success story:


ERDC Point of Contact

Questions about ELAM?
Contact: Dr. Andy Goodwin
Phone: (503) 808‐4872

Intro to the OHWM Manual

Video by Jared Eastman
Introduction to the Interim Draft of the National Ordinary High Water Mark (OHWM) Manual
U.S. Army Corps of Engineers, Engineer Research and Development Center
Jan. 30, 2023 | 24:23
Introduction to the Interim Draft of the National Ordinary High Water Mark (OHWM) Manual for Rivers and Streams.