Understanding deltaic channel dynamics is essential to acquiring knowledge on how deltas respond to environmental changes, as channels control the distribution of water, sediment, and nutrients. Channel-resolving morphodynamic models provide the basis for quantitative study of channel-scale dynamics, but they need to be properly assessed with a set of robust metrics able to quantitatively characterize delta patterns and dynamics before being used as predictive tools. In this work we use metrics developed in the context of delta formation, to assess the morphodynamic results of DeltaRCM, a parcel-based cellular model for delta formation and evolution. By comparing model results to theoretical predictions and field and experimental observations, we show that DeltaRCM captures the geometric growth characteristics of deltas such as fractality of channel network, spatial distribution of wet and dry surfaces, and temporal dynamics of channel-scale processes such as the decay of channel planform correlation. After evaluating the ability of DeltaRCM to produce delta patterns and dynamics at the scale of channel processes, we use the model to predict the deltaic response to relative sea level rise (RSLR). We show that uniform subsidence and absolute sea level rise have similar effects on delta evolution and cause intensified channel branching. Channel network fractality and channel mobility increase with higher-RSLR rates, while the spatial and temporal scales of avulsion events decrease, resulting in smaller sand bodies in the stratigraphy. Our modeling results provide the first set of quantitative predictions of the effects of RSLR on river deltas with a specific focus on the distributary channel network.

Sinkholes can occur on land underlain by dolomite and cause substantial damage to buildings and even loss of life. More than four million people work or reside on dolomite land in South Africa and it is therefore important to be able to construct safely on dolomite land and to minimise the risk of damage to infrastructure and loss of life. Compacted soil mattresses are often used to found structures on areas underlain by dolomite. This study investigated the effect of tensile reinforcement on the behaviour of a soil mattress spanning an underlying water filled cavity designed to impose a cover subsidence sinkhole. Three small-scale models, each consisting of a soil mattress with a cover subsidence sinkhole forming underneath, were constructed and tested in a geotechnical centrifuge. In the first test, an unreinforced soil mattress was tested and in two more tests, reinforced soil mattresses with different reinforcement strengths were tested. The settlement of the unreinforced soil mattress was initially less than that of the reinforced soil mattresses up to the point at which it failed suddenly. Neither of the reinforced soil mattresses failed suddenly, but both experienced large surface settlements that would have led to substantial damage to an overhead structure.