Remote Sensing of Vegetation Characteristics for Estimation of Roughness in Hydraulic Modeling Applications

Project ID: 6034
Principal Investigator: Daniel Dombroski
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2016 and 2017
Keywords: None

Research Question

How can spatially distributed vegetation characteristics (e.g., leaf area index, height, density,
etc.) be derived from aerial LiDAR and digital imagery data in order to parameterize roughness
formulas used in hydraulic modeling?

Need and Benefit

Predicting the hydraulic effects of riparian vegetation within impacted riverine systems is a
growing challenge due to the increasing priority of maintaining ecosystem function while
sustaining water conveyance. Quantitative predictive tools are needed to aid the science,
economics, and policy of establishing environmental flows by addressing questions regarding
the physical interaction of flow and vegetation in rivers and floodplains. These tools are
especially critical for regions of the Western U.S. like Central California, in which multi-benefit
water projects (e.g., projects that enhance flood safety, wildlife habitat, and public recreation)
are legally mandated components of regional and State-wide planning and funding efforts.
These multi-benefit projects can be critically dependent on accurate estimates and modeling of
vegetation effects on hydraulic conveyance due to concerns over increases in roughness
resulting from vegetation establishment and growth.
The existing SRH-2D vegetated-hydraulics solver was developed and tested using prior field
and modeling work on the San Joaquin River near Fresno, CA. Although the model was generally
successful in reproducing the gross hydraulics in the system, it was apparent that extrapolation
of vegetation data measured at small subplots was limiting the ability of the model to represent
more detailed features (Dombroski D. E., 2014).
Although the monitoring and modeling efforts are focused on the San Joaquin River, the insights
generated and tools developed will benefit any large-scale river restoration, monitoring, and
management projects. For example, the Lower Colorado River Multi-Species Conservation
Program (MSCP) has incorporated comprehensive evaluations of vegetation characteristics since
2008; the process-based understanding of prior restoration actions as well as predictive
capabilities would be greatly improved through linkages that quantitatively relate vegetation
characteristics to hydraulic modeling at large scale. The proposed developments will greatly
increase the workflow efficiency of applying the vegetated flow model by minimizing costly and
time consuming ground-based collection efforts. Robustness of model calibration and
sensitivity studies will be improved through greater spatial extent and resolution of observed
vegetation characteristics. The foremost utility of the model is in predicting the change in
hydraulic conditions due to systematic variation in vegetation attributes (e.g., plant growth or
removal through active or passive riparian management).
Aerial mapping using scanning laser and imaging techniques is a powerful tool that is
commonly used in large scale river restoration, monitoring, and management projects. Light
detection and ranging (LiDAR) technology is typically used to measure the height of surfaces and
objects in the landscape below an aircraft, while simultaneous imagery provides a reference
basemap for photogrammetry applications. The geo-referenced photography and digital
elevation model (DEM) produced are necessary for incorporating accurate geometry into a
computational mesh or cross-sections for two-dimensional and one-dimensional hydraulic
models, respectively. The collection of aerial LiDAR data and digital imagery is typically built into
the scope of large scale river restoration, monitoring, and management projects that involve
hydraulic modeling as part of the analysis. Thus the developed methodology resulting from the
proposed work will rely on the manipulation of aerial datasets at little or no additional cost to
the project.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Remote Sensing of Vegetation Characteristics for Estimation of Roughness in Hydraulic Modeling Applications (final, PDF, 2.2MB)
By Daniel Dombroski
Research Product completed on September 30, 2017

This research product summarizes the research results and potential application to Reclamation's mission.

Remote Sensing of Vegetation Characteristics for Estimation of Roughness in Hydraulic Modeling Applications (final, PDF, 2.2MB)
By Daniel Dombroski
Research Product completed on September 30, 2017

This research product summarizes the research results and potential application to Reclamation's mission.


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Last Updated: 4/4/17