LiDar and Its Applications Part 14 – Watershed and Stream Delineation

Basin Delineation

We have discussed the importance of flood management and how LiDar is a great tool for predicative methods. Within flood management there are more specific topic areas within water resource management that can be assisted through LiDar further. Once we start down the rabbit hole though, it is difficult to come out of it lol. We have done a lot research in this series, and we are finding the interconnections of LiDar and environmental management readily. In our article today, we will be focusing specifically on watershed and stream delineation and how that affects various water resources.

Geoprocessing analysis is performed to fill sinks and generate data on flow direction for bodies of water. This is also helpful for understanding flow accumulation, stream length, stream segments, and watersheds. A watershed is an area of land that can drain precipitation in different forms into a location. This location is a body of water such as a stream, lake, or wetland. These bodies of water are vital for the survival of different animal species as well as various plant species. Through geoprocessing data analysis, we can develop representations of these areas and their drainage lines. This can help us lay out an organizational network of how the ecosystems water flow operates.

LiDar Derived DTM

The data we receive on LiDar devices is critical for further development. The main method of investigation done with LiDar is basin characteristic analysis. This is done by using elevation data taken from LiDar devices. Streams and delineation are analyzed through profile curvature, and this can be readily found with LiDar data. This can be done in a 2D snapshot, but 3D visualization gives a more precise understanding of the environment as a whole. The flow paths of streams can be defined with LiDar digital elevation models. This allows us to create multiple sets of basin-characteristic values based on measurements. To further classify these streams, we must then compare and contrast various data sets of different streams.

In order to do this with LiDar in particular, the devices must go through hydrological processing.  This refers to the conditioning, flattening, and enforcing of LiDar data. Hydrological processing can be described as follows: Firstly, horizontal resolution DEMs are created and there is a limited amount of smoothing done to the 3D data terrain. These DEMs are described as pit-filled. The pitfilled DEMs then go through an iterative process of holepunching. This shows any depressions or low elevation than a specific level are removed by a filling process. The process defines a large amount of fill-regions in which the fill is greater than a threshold needed for flow creation. The ease of flow is most important within this process.

Watershed DEM

There are some interesting minutia that allow for different applications and uses of LiDar and 3D data. Although it stems from a standard thought process of analyzing DEMs and DTMs, various fields use different tools to do interesting work that leads to a variety of applications and implementations of this technology.

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