Research

Tidal inletsTidalRangeBarrierWidthMatrix

(in collaboration with Andrew Ashton)

Littoral sediment transport on barrier island coasts can cause tidal inlets to migrate alongshore up to hundreds of meters per year and pose significant hazards and challenges to coastal communities, infrastructure, and ecosystems. We use Delft3D model experiments to investigate how tidal inlets migrate, and how sediment moves around tidal inlets. Parameterizations of sediment movement in and around tidal inlets allow us test and predict tidal inlet migration rates for natural tidal inlets.

Related presentation: AGU 2015

 

 

Wave-influenced deltas

(in collaboration with Andrew Ashton and Liviu Giosan)3.R_WorldDeltas_logaxis

Waves shape the morphology of deltas by transporting sediment alongshore away from the river mouth. We use numerical models and analytical tools to predict the shape of deltas, and to estimate how waves rework deltas in the face of extreme reductions in fluvial sediment supply caused by river damming.

Related publications: Nienhuis et al 2013, Nienhuis et al 2015

 

River mouths

(in collaboration with Andrew Ashton, Liviu Giosan, Sergio Fagherazzi, William Nardin)FigS2_BypassingMatrixHs-01-01

Near the river mouth, combined jet and wave dynamics, along with morphodynamic feedbacks, control the fraction of sediment transported alongshore by littoral currents that can bypass the river channel. We study how different bypassing rates influence large-scale delta evolution and examine the effect of waves and the river mouth jet on alongshore sediment bypassing. We implement parameterizations of bypassing from Delft3D into larger-scale coastal evolution models to investigate the interaction between river mouth processes and delta morphology.

Related publication: Nienhuis et al 2015, Nienhuis et al 2016

 

Global deltas

(in collaboration with Andrew Ashton, Doug Edmonds, Albert Kettner, Joel Rowland, Tor Tornqvist)AllDeltasRTW

Coastal deltaic change is expected to be one of the major Earth-surface hazards of the 21st century as deltas around the world face large changes in sediment supply due to river damming, land-use changes and climate change. We have combined estimates of present and future sediment delivery and wave climates to predict the future morphologic response of about 14000 deltas worldwide.

Related presentation: Ocean Sciences 2016

 

Bedforms

(in collaboration with Taylor Perron, Peter Traykovski, Justin Kao, Paul Myrow, Katie Samuelson)Fig7_SepZone-01

Sand ripples formed by waves have a uniform wavelength while at equilibrium and develop defects while adjusting to changes in the flow. Ripples driven by tides grow at a characteristic wavelength, but then reverse orientation when the flow direction changes. We have developed a Lattice Boltzman numerical flow model to study bed shear stress patterns generated by bedforms driven by unidirectional or reversing flow.

Related publications: Nienhuis et al 2014, CSDMS 2015

 

 

Crevasse splays

(in collaboration with Tor Tornqvist)

Crevassing is an important mechanism for land building in deltaic areas. We developed a morphologic model of crevasse splays to investigate the effect of compaction and vegetation on crevasse lifetime and sediment volumes.