Topobathy Lidar: Specifications and Experiences

Hosted by the ASPRS Bathymetric Lidar Working Group, this session will begin with presentations highlighting projects conducted in diverse environments (coastal, bay, estuarine, and riverine) and will conclude with a discussion of bathymetric lidar specifications and best practices proposed by federal and industry partners. 

JALBTCX BathyLidar Specification Update

Over the past two years, federal partners have convened to establish a specification for bathymetric lidar. The ASPRS Bathymetry Working Group aims to engage the community at large, soliciting comments and suggestions on the specification; promote professional practices that meet the specified requirements; and identify educational opportunities to address bathymetric knowledge gaps. Hear how various topobathymetric lidar sensors performed in diverse environments, from coastal and bay to estuarine and riverine; the processing approaches for such differing datasets; and any lessons learned. The Working Group will then share the status of the specification, opening the session for discussion and soliciting feedback.

Xan Fredericks, USGS & Nick Johnson, USACE JALBTCX

Topo-Bathymetric Lidar Surveys of Rivers: From Improved Fish Habitat and Fish Passage to Enhanced Flood Hazard Mapping

Our research group has been operating their Leica Chiroptera 4X system since 2014 and have conducted numerous research projects for benthic habitat seafloor mapping in the coastal zone. More recently they have also begun TB-lidar surveys of rivers in Eastern Canada with the focus of mapping fish habitat and fish passage. In addition, they have demonstrated how TB-lidar surveys of rivers can improve hydraulic models of fluvial flood hazard mapping with improved channel geometry and river cross-sections. The ability of TB-lidar top capture the water surface and the riverbed allow for water depth maps to be calculated. These maps can then be inverted and used to calculate a “cost” surface where the least cost path is derived which traverses from deep pool to deep pool. This method is superior to deriving stream longitudinal profiles from topographic lidar using the D8 watershed method which suffer from being artificially too long because the water surface can cause the algorithm to jump from riverbank to riverbank. The long profiles derived from TB-lidar highlight the pools and potential impediments to fish travel such as waterfalls and other shallow areas. TB-lidar integrated with thermal sensors provide insights of deep pools where fish can take refuge during the summer in low flow conditions. The data can be input into hydrodynamic models where the flow can be increased or decreased to evaluate flooding or possible passage issues for shallow areas. 

Tim Webster, Nova Scotia Community College

Utilizing Multiple Topobathymetric Lidar Sensors for Mapping in the State of Florida

Since 2020 Dewberry has had the opportunity to acquire topobathymetric lidar for multiple projects around the state of Florida utilizing several different topobathymetric lidar sensors. These areas include the coast lines along both the Gulf of Mexico and Atlantic Ocean, as well as bays, estuaries, riverine environments, and springs systems. The sensors utilized consisted of varying system configurations and performance expectations. This has provided Dewberry the unique opportunity to test the performance of several topobathymetric lidar sensors in the varying coastal environments around Florida. This presentation will discuss successes and challenges experienced by Dewberry along the way.

Emily Klipp, Dewberry

Multi-Year Sediment Volume Analysis of the Platte River Using Topobathymetric Lidar to Support River Management

The Platte River floodplain in central Nebraska is a shallow braided planform that provides critical habitat for threatened and endangered species.  Protecting and restoring this habitat is a primary objective for the Platte River Recovery Implementation Program (PRRIP). To manage water and riverine habitat for target species efficiently and effectively requires detailed understanding of geomorphology and how flows impact topography and vegetation throughout a given year. Characterizing the change as impacted by anthropogenic and natural processes is of paramount importance to resource management goals.  

To do this, PRRIP contracted a multi-temporal acquisition of topobathymetric lidar over a 90-mile reach of the Platte River floodplain to document annual sediment movement and riverbed change. Sensor selection and processing methodology is essential to creating a dataset that can support geomorphologic change detection. Achieving a high level of accuracy, both absolute and relative, by removing systemic error between years from a dataset is paramount to providing meaningful sediment volume analyses of aggradation and degradation, one of the primary study objectives for PRRIP. This requires a robust survey plan, sensor calibration and alignment, water identification, and complex shallow water refraction processing. This error would typically be within standard accuracy specifications, but the ability to leverage multiyear acquisitions demands additional considerations.

Andres Vargas, NV5 Geospatial

From Marshy Coasts to Pacific Isles: Insights into the Acquisition and Production of Topobathymetric Lidar Data in Varied Coastal Environments

Airborne topographic bathymetric (topo-bathy) lidar is a valuable tool for surveying coastal waters, with the potential to collect seamless topography and bathymetry in one aerial pass. During the 2022-2023 field season, Woolpert has flown fixed-wing topo-bathy lidar over Chincoteague Bay & Chesapeake Bay in Maryland/Virginia, the marshy coast of the Northern Gulf of Mexico, and conducted OCONUS surveys in American Samoa and Hawaii for the National Oceanic and Atmospheric Administration’s National Geodetic Survey. These surveys support the provision of data for shoreline mapping, natural disaster response, and infrastructure, among a myriad of other potential downstream uses. Such differing environments each posed their own obstacles to successful data delivery: this presentation will highlight some of the Woolpert team’s challenges and adaptations for acquisition and production in reference to this wide range of coastal environments.

Nicholas Wilson, Woolpert