Experience is our tool

Waternet has shallow waterways surveyed with bathymetric LiDAR - July 2015

PolderGrootWilnis In the coming years in the polder Groot Wilnis Vinkeveen secondary and tertiary ditches will be deepened to a minimum of 50 cm depth with the objective to increase the water flow and thus improve water quality. Landowners in the area are responsible for the deepening and maintenance of the often shallow waterways under their ownership. Waternet verifies and maps the depth of the water system. Traditionally, this is done using dipsticks. However, this is a time consuming process.

In 2013, Waternet approached Periplus Consultancy BV to identify which techniques are suitable to measure these shallow waterways. The focus was on techniques that can be applied in a better, faster and / or cheaper way. Airborne acquisition methods (satellites and aircraft) appear to be the most promising. In contrast to most land or water acquisition methods, no permission for property access is required from the landowner. In addition, the acquisition speed is much higher than when conventional methods are used.

Lidar

Since the resolution (horizontal and vertical) of current satellite images is not yet high enough to accurately measure narrow waterways, in consultation with Waternet it was decided that the next phase of the project would only assess the employability of bathymetric LiDAR. For this purpose leaders of bathymetric LiDAR and companies that use bathymetric LiDAR for acquisition were approached in 2014. Through questionnaires companies could indicate what equipment they would deploy for depth acquisition of shallow, narrow waterways, what the specifications of these devices are and what experience they have in similar projects.


bathymetric Three companies and sensor manufacturers were then invited for interviews – in each presentation actually one type of bathymetric LiDAR was addressed, in which producer and executive party could explain the possibilities and limitations of the system, tailored to the local conditions. In addition, examples from previous projects were shared. All parties gave the impression that the technical challenges had been sufficiently examined and that the required accuracy could be attained.

In the last phase of the project, Periplus Consultancy BV, in collaboration with Waternet and the Waterschapshuis, prepared a Scope of Work. Due to favorable ecological conditions (little vegetation and clear water), the acquisition occurred early spring 2015. The company Aerodata Surveys Nederland has implemented the acquisition with a bathymetric LiDAR Leica. The first results are expected this fall.