Coastal Inundation Mapping Training

As Peninsula Urban Forestry’s primary ArcGIS user, I had the great pleasure of attending a 2-day course on coastal inundation mapping put on by WA Coastal Training Program and instructed by NOAA professionals Matt Pendleton and Billy Brooks. After a early morning scenic drive from our base here in Port Angeles, I arrived at one of South Puget Sound Community College fantastic computer labs for the class. With a small class size of around 15 students and two amiable instructors the class was the perfect mix that allows for informal discussion of the topics being covered, while still progressing quickly through the material. Though the majority of attendees were solely GIS professionals, I was not alone as a GIS user with an environmental focused background. Also present were ecologists, habitat biologists, and a couple others. This highlights what I believe we will be seeing more and more of as these technologies become increasingly accessible. Even a small consulting firm can devote the time to learn a few basic skills that will aid assessment and presentation of findings on a wide range of projects. You don’t need to know how to use every tool in a master carpenter’s tool box to do some sanding or put in some nails. That is a good thing too because, with a toolbox as expansive as ArcGIS, it can be easy to get lost.

What We Learned

That is where this course comes in. It starts with GIS basics to make sure everyone has a solid base for all the upper level analyses to follow. This covers such topics as the different types of datums we be work with, how they were established, and how to connect and convert them to achieve our goals while staying accurate and consistent with our data. It also covered the inherent difficulties involved with trying to measure all the data required for accurate mapping: topographic, bathymetric, tidal levels, and project specific information. LIDAR cannot accurately represent elevation under water, and the vessels used for gathering that bathymetric data cannot access areas of shallow water, so only as technologies advance are we able to assess certain areas where previously we made assumptions. There are also a multitude of sites to acquire data, and to a beginner it can be difficult to determine which data is the right data for the project. The adage “junk in, junk out” applies all too well here. If you attempt to do an analysis on a set of data that does not have the appropriate resolution, or it is using a different coordinate system, or is out of date, the information you get out of it is almost less useful than no information at all. At best you’ve wasted time on a useless product, at worst it can lead you to false conclusions.

 

How We Used It

Once we were informed on the relevant types of data, where to acquire them, and how to determine their quality, we were well equipped to begin running exercises on coastal inundation mapping. As a hands-on learner, this class did it right in my book. There were plenty of exercises to practice and drive home the main points of the lectures. These started off fairly basic, connecting tidal data to national vertical and horizontal datum, then using tidal gauge to map storm surge extent, until eventually we combine all the lessons to map potential sea level rise associated with storms and/or climate change to identify vulnerable communities.

Applicability to Other Services

Much of the information I learned in this class can be applied to other aspects of my work. Many of the projects we do at Peninsula Urban Forestry involves critical areas, such as steep slopes, wetlands, and shorelines, where elevation data can be vital. I’ve learned skills that improve our workflow and instill more confidence in the end product for these types of projects. The course also allows us to provide additional services, such as assessing the vulnerability of communities to ocean inundation. This is an important long-term strategic consideration that many coastal communities need to address before it becomes an issue. Inundation from a strong storm surges can cause damage to infrastructure, vegetation, and in the worst cases result in loss of life. One of the best ways to handle the issue is to evaluate risk and implement plans that address our most vulnerable communities or areas. By mapping inundation at various degrees of severity, we can see where the extent of flooding is likely to be, what critical areas that may be impacted, and how to mitigate for that risk.

 

Future Uses

As a wetland biologist, one of the most interesting ideas the class raised for me was mapping just how much coastal vegetation can reduce the impacts of inundation events. It is a well-known benefit of wetlands that they reduce the damage caused by storms by absorbing energy from wind and water. Viewing the difference in storm damage between unvegetated coastal regions and those vegetated by mangroves is eye-opening. There is some research into quantifying that actual service provided by coastal vegetation, with at least a few studies using 3D modeling to assess how much vegetation reduces inundation. Using the best available science, it would be possible to display these potential benefits to a community by using a layer for vegetation that alter the amount of inundation expressed during the processing we learned in this course. This would be useful for helping communities determine how much they should be investing in preservation of vegetation or revegetation, by showing the extent to which that investment would reduce their risk. As more research comes out on the topic better models will be made, and from them better maps.