Hydrography Network

Mapping of streams and rivers over very large areas has always been iterative and expensive. Now Digital Elevation Models (DEM), surfaces and topography derived from LiDAR are revolutionizing the way we represent and analyze surface waters. We will have truly 3-dimensional models and measurements, allowing new analyses of total flow accumulation, flow predictions, regional management decision support and more. This application sharing network can aid in thinking through the changes by sharing ideas and tools.

Click on a topic below to see available articles and guidance documents

Topographic Wetness Index (TWI) calculated from LiDAR and used to identify potential overland flowpaths. Source: Susquehanna River Basin Commission, 2016

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If you are interested in joining the Hydrography application network please complete the form below and and click the "Submit" button. Members of the network may be invited to attend conference calls or meetings and will be able to submit reference materials such as tools, code, scripts, papers, etc.

General Hydrology Information
Date Current
Summary A website hosted by PA MAGIC that presents the Water Data Initiative in Pennsylvania. Goals, milestones, reports, background documents, and contact information are provided for GIS professionals who may be interested in joining the initiative.
Citation NA
Read Time 15 minutes

Flow Path Modeling
Author David Saavedra
Date July 2018
Summary This paper describes the standard practices used by the Conservation Innovation Center (CIC) to derive Enhanced Flow Path (EFP) datasets. Data processing techniques are discussed (hydro-conditioning as a pre-processing step and flow accumulation as the central derivation method), as are the limitations of these techniques.
Citation Saavedra, D. (2018). Enhanced Flow Path Methods Overview: Conservation Innovation Center and Chesapeake Conservancy, 6 p. Accessed from: https://chesapeakeconservancy.org/wp-content/uploads/2018/07/CIC_Enhanced_Flowpath_Methods_20180703.pdf
Read Time 15 – 20 minutes
Author Matthew Baker, David Saavedra, Michael Norton
Date October 2018
Summary This paper compares the suitability of different detection methods for deriving stream flow paths in different environments. In addition to the main research, a comprehensive literature review covers such methods as: process-based methods, direct-detection methods, geomorphons, and cartographic and geomorphic elimination. The authors discuss in detail their approaches to fieldwork, processing elevation data, detecting channel-like depressions, constructing channel skeletons, comparing detection methods, constructing channel networks, estimating channel width and bank height, and estimating flow permanence. The overall emphasis of this work is on geomorphon analysis and the best geomorphon parameters for individual environments. Baker et al. selected 14 study sites covering five different physiographic provinces to evaluate the applicability of various methods of mapping and data acquisition in different geographies.
Citation Baker, M., D. Saavedra, and M. Norton (2018). Scope #10: Methodology for developing high- resolution stream and waterbody datasets for the Chesapeake Bay watershed: Conservation Innovation Center and Chesapeake Conservancy, Report to Chesapeake Bay Trust, 59 p. Accessed from: https://cbtrust.org/wp-content/uploads/2018_Scope10_FinalReport_wAppendix.pdf
Read Time 2.5 - 3 hours
Author Abigail Schaaf, Robert Vaughan, Brent Mitchell
Date Current
Summary In this tutorial you will explore lidar bare earth DEMs (digital elevation models) as they can be utilized for hydrography modeling, including: hydro-conditioning and enforcing the DEM, and creating stream networks.
Citation Schaaf, A., R. Vaughan, and B. Mitchell (2018). Hydro-Modeling with LiDAR Bare-Earth DEM in ArcGIS Tutorial, 17 p. Accessed from: https://www.fs.fed.us/eng/rsac/lidar_training/Considerations%20for%20Hydro%20Modeling%20with%20Lidar%20DEM%20output/story.html
Read Time 1 - 2 hours

Flow Predictions
Author Jeffrey Zimmerman, James Shallenberger
Date October 2016
Summary The process described herein uses a type of digital terrain analysis (DTA) resulting in a Topographic Wetness Index (TWI) that quantifies topographic controls of basic hydrological processes. Upon completion, TWI raw output is displayed as a dimensionless linear color gradient, with starting and ending point colors based on the minimum and maximum flowpath intensities unique to each catchment.
Citation Zimmerman, J. and J. Shallenberger (2016). GIS Topographic Wetness Index (TWI) Exercise Steps, 14 p. Accessed from: https://www.srbc.net/pennsylvania-lidar-working-group/docs/twi-srbc.pdf
Read Time 30 minutes - 1 hour

Flow Accumulation
Author Greggory Mirth, Eric Jespersen
Date October 2016
Summary The technical companion piece to the overview document discussing Indiana University of Pennsylvania’s efforts towards data processing and creation. This is a more technical description of the work done. The central workflow in these papers is focused on flow accumulation as a means of deriving flow paths; however, this technical report provides more detail with regards to workflow and the computational tools utilized. Includes a brief discussion/comparison of geospatial software.
Citation Mirth, G. and E. Jespersen (2016). Extracting Hydro Data from Multiple LiDAR Series: USGS Contracted Project (funding opportunity number USGS-15-FA-0516) and collaboration with Lancaster County, PaMAGIC, and Indiana University of Pennsylvania, 29 p. Accessed from: https://pamagic.org/sites/default/files/documents/Water%20Data/G15AC00516Technical%20Report_revised%20%20final_20161130.pdf
Read Time 1.5 - 2 hours

Finer-Scale Hydrology Data
Author Eric Jespersen, Glenn Mohler, Robert E. Wilson
Date October 2016
Summary A companion piece to the technical report discussing Indiana University of Pennsylvania’s efforts towards data processing and creation. This is a more general description of the work done with additional findings and recommendations for a statewide application. The central workflow in these papers is focused on flow accumulation as a means of deriving flow paths.
Citation Jespersen, E., G. Mohler, and R. E. Wilson (2016). NHD Pilot Project for Lancaster County – Project Overview and Findings: USGS Contracted Project and Collaboration with Lancaster County, PAMAGIC, and Indiana University of Pennsylvania, 19 p. Accessed from: https://pamagic.org/sites/default/files/documents/Water%20Data/G15AC00516OverviewReport_revised%20final_20161110.pdf
Read Time 45 minutes - 1 hour

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