Speeding up stream mapping

Posted on March 23, 2015

Information on stream cross-sections is a basic requirement in many areas of hydraulic design, flood control, water resource planning and ecological restoration. Traditionally, cross-sections are plotted by using weighted lines to take a series of soundings across the channel. This can be an expensive process in terms of labour, time and money. Also, when streams are fast-flowing, data collection may be dangerous and the sounding line may drift downstream, leading to bias which is difficult to correct for. Recently, alternative techniques that rely on ground-penetrating radar (GPR) for the measurement of stream cross-sections have been introduced. GPR-based systems are superior to the sounding line approach because they are more cost-effective and can quickly capture and process large amounts of continuous, high-resolution data. They are also safer because they don’t involve contact with water. The main constraint on the use of GPR for stream cross-section work has been data interpretation, which has relied on input from highly trained experts. This drawback has now been overcome by using a form of time-series analysis (the Hilbert-Huang transform) to decompose and clarify GPR signals. Comparisons of field data sets from the Beishi River in Taiwan showed very close agreement between stream cross-sections based on the new technique and the weighted-line method.

Reference: Yen-Chang Chen et al. 2014. Measurement of stream cross section using ground penetration radar with Hilbert–Huang transform. Hydrological Processes 28, 2468–2477.