Proposed retrofit for sediment settling velocity tubes (SVTs)

In order to determine the distribution of sediments, bottom-withdrawal settling velocity tubes (SVTs) are used. This technique is, for example, often applied in estuaries. Yet, these tubes have serious disadvantages. Several papers call for the use of video applications in preference. However, not only that this technique has many disadvantages as well, it generally does not suit the need of hydro-/marine geochemical research. Particularly if a project needs to analyse different fractions separately, for example in order to determine and model the transport of suspended materials, video analyses are not a feasible alternative. Therefore, this note aims to describe a number of improvements to compensate for previously observed weaknesses. Particularly the addition of a simple funnel, mimicking a natural environment without walls, could increase the general reliability of bottom-withdrawal techniques with sediment settling velocity tubes.