Author: GEOCUE GROUP
Rising sea levels and high tides continue to make a noticeable impact on coastline communities and the environment. As a result, geospatial professionals and surveyors monitor affected areas. The overall goal is to accurately assess and prioritize solutions in the hopes of preventing future occurrences. With reports predicting the continuation of sea levels and high tides to rise, many cities bordering the coastline are concerned.
Seawalls are designed to prevent upland erosion and storm surge flooding; Coastline cities utilize seawall structures to help maintain these issues. Currently, the City of Miami Beach, Florida has approximately a total length of 57 miles of seawalls. However, low lying seawalls have contributed to many flooding events over the years.
In 2019, the City Commission of Miami Beach and the Sustainability and Resiliency Committee assigned the Department of Public Works to develop a strategy for assessing the seawall elevations within the city. The goal was to promote and encourage neighbours to reconstruct their seawalls and join the city in its resilient efforts to create a continuous barrier throughout the city.
In conjunction with the City of Miami Beach Survey Department, GIS Manager, Nestor Navarro, and City Survey Manager, Brian Bellino researched different data collection methods, both internal and external (i.e., consultant manned aerial/boat LIDAR) to conduct this project. After further analysis, the research presented that the out-sourcing methods were too expensive and soon realized drone collection would be the preferred method.
Photogrammetry vs Drone LIDAR
At first, Mr Navarro considered conducting the project by Drone photogrammetry using the DJI M200 partnered with GeoCue’s Loki GNSS PPK Direct Geo-positioning System. However, quickly noted that using drone LIDAR for this project would give them the following advantages:
Ability to penetrate vegetation
Ability to conduct flights regardless of the weather conditions
Post-processing times are much faster
Point Cloud generation times are much faster
Following careful consideration and research, the Department of Public Works decided to use the drone LIDAR collection method. By bringing this technology in-house they were able to reduce cost, achieve the best quality, and avoid the need to access private properties.
True View 410 3DIS
As result, the City of Miami Beach invested in GeoCue’s True View 410 3D Imaging System allowing the ability to collect LIDAR and photogrammetry in a single flight.
The team conducted a 57-mile drone LIDAR/Imagery survey deploying their DJI M600 Pro drone partnered with GeoCue’s True View 410 3DIS. With the collected LIDAR and imagery data, they were able to digitize approximately 2,500 seawalls in GeoCue’s EVO software. The elevations were transferred to an ArcGIS database and linked to each property. The team was able to quickly generate colourized 3D point clouds, orthophotos, digital elevation models, digital terrain models, contours, elevation extractions and more. These deliverables were compiled and displayed on the city’s Geocortex web viewer environment. This environment easily displays seawall elevations, jurisdictions, types, owners, etc., all tied to control reports from True View capture.
With this data, the City of Miami Beach Public Works Department was able to present their analysis to the commission in September 2021 and make suggestions based on their analytic drone LIDAR data to prevent future flooding.