Stormwater Pond Surveying: Why Probe When You Can Ping

Jennifer Leslie, Hayden Easton, S Speed - Pattle Delamore Partners, Auckland and Auckland Council, Auckland , 01 April, 2019

A new method of surveying stormwater ponds is saving time, increasing data quality and reducing health and safety risks. It involves a remotely-controlled Oceanscience Q-Boat 1800D (Q-Boat) deployed with a SonTek HydroSurveyor M9 Acoustic Doppler Current Profiler (ADCP) collecting accurate bathymetric and position data, which can be used for multiple applications.

Auckland Council manages nearly 500 stormwater ponds across the Auckland region, so stormwater pond maintenance works present a significant cost. To prioritise pond maintenance, Pattle Delamore Partners (PDP) and Auckland Council are using this new methodology to calculate sediment accumulation volumes, by comparing the ADCP bathymetry results to the as-built drawings of the ponds. This information is used to determine whether the stormwater pond is functioning efficiently, whether dredging maintenance is required and where the greatest deposition of sediment is occurring within the pond. Having an estimate of the sediment volume that requires removal, can also assist with obtaining an indication of dredging costs.

There are numerous advantages that the Q-Boat and ADCP methodology has over the traditional manual probe surveying method including faster data collection, greater data accuracy and reduced health and safety risks. In addition, comparative evidence between the two methods suggests that the manual probe surveying method may actually be compromising the integrity of the ponds.

The field techniques used to collect and process the data will be detailed and the potential uses of the data outputs explored. The benefits and shortfalls of this new method compared to the traditional manual probe surveying method will be evaluated, using examples. Case studies of other projects where the new methodology has been applied will be presented, including a bathymetric survey of an estuary and a marine port.