Mapping Urban Drainage with Airborne LIDAR using LP360
Published On: January 11, 2018
Publicly funded Airborne LIDAR data is now becoming ubiquitously available in many parts of the country and has been widely used to support high resolution topographic and floodplain mapping. Recently, the USGS identified Quality Level 2 (QL2) LIDAR as having the broadest application and value for the cost. Once collected, much of this data is available to design professionals at no cost.
Using LP360 software in conjunction with ArcGIS Spatial Analyst to support urban drainage mapping, GroundPoint Engineering has been able to demonstrate that QL2 LiDAR can adequately characterize water flowing across urban and suburban environments in a wide range of terrain types. The resulting highly accurate drainage calculations have been integrated with standard storm water methods to estimate peak flows at culverts, catch basins, and key municipal storm water outfall locations.
Today we will provide an orientation to the workflow and how LP360 software specifically is used to support high resolution drainage mapping by examining projects conducted in Los Angeles, CA, Pittsburg, PA, and Kingston, NY.
The first scenario was conducted with Pennsylvania metro, Pennsylvania University and Pennsylvania Department of Transportation. The focus of this project was mostly on small scale run off in a small neighborhood with aging infrastructure. The area was experiencing runoff and peak flow issues with their infrastructure. They were also interested in the effects of salt loading in the winter and where contaminated runoff transfers between properties.
The second project was conducted in Ulster County in Eastern New York State with Cornell University. The goal of this projects was to work on a set of quantitative models that evaluate culverts. In this area, whenever there is a wash out, or infrastructure is too small to handle current runoff conditions, they come out with equipment doing retro-fits and repairs on an emergency footing basis. Instead, they wanted to find out the capacity of their current culvert, what the drainage area that contributes to that culvert is, and what is the anticipated peak flow so that they could prioritize which culverts they might want to proactively replace.
In Los Angeles County, the project was conducted in an area that is highly developed in some areas and rural desert in other areas. Their MS4 program is in consent decree because they have runoff issues. Every time it rains, they have to close the beaches. For this project, they wanted to look at how to manage drainage and needed to figure out where everything drains.
First, we perform a Surface Prep workflow which includes the following steps:
- Original DEM
- Fill Sinks
- Flow Direction
- Flow Accumulation
- Are breaklines still needed?
- Yes- Highways, gutters, sink mask, berms, voids, centerlines
- Modified DEM
- Go back to step 2
- No- Begin Modeling
Original and modified DEM are exported from LP360. LP360 tasks include re-classifying points and adding breaklines to clean up the DEM and get it ready for modeling
Once the surface prep work is completed, you can move to the modeling workflow
- Surface Prep
- Accumulation Threshold
- Stream Network
- Catchment polygons
- Pour point analysis
- Pour point adjustments OR Merge Catchments
About Benjamin Houston
Benjamin Houston has over 25 years of experience with mapping technologies, both from military applications, environmental conservation and public works. He is a licensed professional engineer in New York and has a background in public health engineering, utilities infrastructure and storm water management. He has worked as both an engineer and a GIS analyst in for-profit and non-profit companies, as well as with various local government agencies. Ben is a former Army officer and spent twelve years as a topographic engineer, public health engineer and special operations team leader before coming back to the private sector. Ben is a graduate of the U.S. Army Combined Arms Services Staff School, Defense Mapping School and the JFK Special Warfare Center and School, and he completed a tour of duty in Afghanistan in 2002.
For the past ten years his focus has been on using urban LIDAR data for topographic mapping and doing rastor-based terrain analysis. He most recently began working with small drones to enhance their value as a survey and mapping tool. He is also an adjunct professor of GIS at the Bard Center for Environmental Policy and was elected to the New York State GIS Association Board of Directors in 2017. He is a certified project management professional, certified GIS professional, he got his B.S. in Geological Engineering from Colorado School of Mines and M.S. in Hydrogeology from North Carolina State University. Ben has been using LP360 for about ten years.