on the order of the overall numerical discretization error. The temporal discretization was done with Implicit-explicit (IMEX) schemes. Among other schemes, we specifically used an IMEX 3rd order scheme, which uses a third order Adams-Bashforth scheme for the convective term and a third order Adams-Moulton for the Diffusion term – The first order IMEX scheme analogously uses a combination of Euler schemes.

The data was analyzed mainly using a conventional algorithmic approach but also an exploratory citizen science approach described in the outlook. The algorithmic approach used a signed distance field calculation [@JBS6] where distances were computed from triangle mesh representations of the RIVs. A distance field for a surface is a mapping, $d: \mathbb{R}^3 \rightarrow \mathbb{R}$, from a point in space, $\mathbf p$, to the distance from $\mathbf p$ to its closest point on the surface. The sign of the distance field allows us to tell inside from outside, and the largest interior distance is also the radius of the largest sphere fully contained in the RIV. To compute the distance efficiently at a given point, $\mathbf p$, a bounding box hierarchy was used to find the triangles most likely to contain the point at a closest distance to 