Leeston Flood Visualisation

In this unique project Mappazzo combined drone survey with results of 3D flood modelling to deliver material that would help the community of Leeston visualise the impact of predicted flooding in their town.

The Mappazzo team has used a series of advanced techniques and experimental workflows to push the limits of drone based survey and used outputs of that survey for advanced GIS analysis and 3D animation to prepare various perspectives of the predicted flood.

Background

Leeston is a small rural town in the Canterbury region of New Zealand. The town has been built along Leeston Creek which is prone to flooding.

After a major flood in 2013, the community asked their local council (Selwyn District Council) to investigate the dynamics of the flood risk, and to invest in flood protection infrastructure. A flood bypass is now under construction to mitigate the most significant impacts of future flood events.

With many years past and construction well underway, the Council wanted to provide the Leeston community with a new tool to help understand the extent of inundation that is expected to occur during a major flood.

Photogrammetry with oblique photographs

The Mappazzo team completed a series of drone flights to capture photos required for photogrammetry processing (drone survey) but this project posed a unique problem in that the study area covered large number of landowners.

Aviation law in New Zealand requires operators to gain explicit permission from landowners beneath a drone flight path, which created a potential administration nightmare for the project. To avoid potential delays and unnecessary complexity caused this requirement there was a desire to complete the flights only over road reserves.

Ordinarily photogrammetry is completed using photos taken NIDAR (looking straight down), which simplifies the data processing workflow and limit errors in the final data set. To avoid flying over private land, Mappazzo supplemented the commonly used NIDAR photo series with additional photos taken at an oblique angle. This unique (experimental) approach allowed us to capture the whole study area without any flights over private property.

New perspectives of the Leeston flood risk

Mappazzo use the latest professional software and purpose built computers to take drone photos and turn them into a 3D model of the town, then we applied bit of GIS wizardry and some advanced animation techniques to generate maps and video animations.

The resulting maps, images and animations will assist Selwyn District Council and the Leeston community to plan for future floods and mitigation infrastructure.