Heidi M. Nepf

Ph.D. 1992, Stanford University
Associate Professor
Civil and Environmental Engineering
Margaret MacVicar Faculty Fellow
MIT
Room 48-423
Phone: (617)253-8622

 

heidi nepf pic
 

Environmental Fluid Mechanics:
 

IAHR Environmental Fluid Mechanics Short Course. June 7-16, 2004

  

marsh pic
Sippewissett Marsh, Cape Cod
 

Research Highlights:

    

Vegetation Hydrodynamics
Fresh and salt-water wetlands are important transition zones that control exchanges of sediment, nutrients, and pollutants between terrestrial and aquatic systems. Wetland plants contribute directly through uptake and biological transformation and indirectly by altering the hydrodynamic regime. Submerged vegetation, such as seagrasses, serve a similar role in coastal regions, controlling nutrient loads and altering water clarity by promoting particulate deposition. Professor Nepf's research examines the hydrodynamic aspects of vegetation, e.g. the turbulence and transport processes associated with flow through and around aquatic canopies, in relation to canopy morphology, flexibility, and degree of submergence. The goal is to understand the effects of vegetation on marsh and coastal hydrodynamics, and to use this understanding to describe the role of aquatic vegetation in controlling particulate and pollutant fate in coastal regions.

eelgrass pic

A plastic model of eelgrass was created by graduate student Marco Ghisalberti to study the onset of monami and its impact on vertical exchange between a submerged canopy and overlying water column. The plastic model is dynamically similar to real seagrass in rigidity, buoyancy, and drag profile [photo by Marco Ghisalberti].
 
nepf figure pic
Flow speed, U, is reduced by vegetative drag within the canopy. The strong shear (high equation image) at the top of the canopy produces a string of coherent vortices (blue), known as a Kelvin-Helmholtz vortex street. The passage of these vortices creates positive velocity perturbations (u') at the top of the canopy that bend the canopy forward. Thus, the signature of the vortex street is a bending wave that progresses along the canopy and is called a 'monami'.
[Funded by: National Science Foundation]

Littoral Wetlands and Inflow Dynamics

mystic lake pic

Field studies of the exchange flow between the shallow
forebays and main basin of the Mystic Lake, Winchester, MA.

This project examines the role of littoral wetlands in mediating the flux of river-born nutrients/pollutants into the coastal regions of a lake. The thermal capacity of the wetlands can influence the temperature of the lake inflow, and thus the fate of the inflow within the lake (plunging vs. surface outflow). This affect is controlled by the residence time of the wetland and the magnitude and direction of diurnal and seasonal heat fluxes. The residence time, in turn is controlled by the competing effects of wind-, buoyancy- and river-driven circulation. In the next year we will combine numerical modeling and field observation to better define the thermal capacitance of the forebays and the impact on river-inflow fate within the lake.

[Sponsored by: National Science Foundation, National Institute of Health]

 
 

Internal seiches provide an important conduit from wind input to mixing energy within lakes. Analytic solutions suggest that the distributions of internal wave energy is strongly dependent of bathymetry. For example, seiche motions are amplified in shallow regions, leading to enhanced local mixing and greater tendency for upwelling. A combination of field, laboratory and numerical studies is being used to examine the dynamic significance of simple bathymetric variation as well as the potential impact on bed-source contamination.

[Sponsored by: National Institute of Health]

Bathymetric Control of Internal Wave Dynamics
 

Selected Publications

With permission from some of our publishers, we have been able to put up some articles as Acrobat .pdf files here for your personal research and study. You can download Adobe Acrobat Reader for free if you don't already have it.

Palmer, M.R., H.M. Nepf, T.J.R. Pettersson, and J.D. Ackerman (2004). Observations of particle capture on a cylindrical collector: Implications for particle accumulation and removal in aquatic systems. Limnol. Oceanogr. 49: 76-85.
The Article

White, B. and H.M. Nepf (2003). Scalar transport in random cylinder arrays at moderate Reynolds number.Ý J. Fluid Mech. 487:43-79
The Article

Ghisalberti, M. and H. Nepf (2002).  Mixing layers and coherent structures in vegetated aquatic flow. J. Geophys. Res.,107(C2):1-11.
The Article

Andradottir, A. and H. Nepf. (2001).  Impact of exchange flows on wetland flushing. Water Resources Research, 37(12): 3265-3273.
Abstract   The Article

Nepf, H. and E. Vivoni (2000).  Flow structure in depth-limited, vegetated flow." Journal of Geophys. Res.105(28): 547-28, 557.
The Article

Andradottir, H. and H. Nepf. (2000).  Thermal mediation in a natural littoral wetland:Ý measurement and modeling. Water Resources Research, 36(10): 2937-2946.

Knauer, K., H. Nepf, H. Hemond (2000).  The production of chemical heterogeneity in Upper Mystic Lake." Limn.& Ocean, 45(7):1647-1654
The Article

Andradottir, H. and H. Nepf (2000).  Thermal mediation by littoral wetlands and impact on lake intrusion depth." Water Resources Research,36(3): 725-735.
The Article

Fricker, P., and H. Nepf (2000).  Bathymetry, stratification, and internal seiche structure.   J. Geophys. Res.,105(C6): 14,237 - 14,251.
The Article

Nepf, H. and E. Koch (1999).  Vertical secondary flows in submersed plant-like arrays." Limn. Oceanogr.,44(4): 1072-1080.
The Article

Nepf, H. (1999).  Drag, turbulence and diffusivity in flow through emergent vegetation." Water Resources Research,35(2): 479-489.
The Article

Nepf, H., C.H. Wu, and E.S. Chan (1998).  A comparison of two- and three-dimensional wave breaking,  Journal of Physical Oceanography, 28(7): 1496-1510.
Abstract

Nepf, H., C. Mugnier, and R. Zavistoski (1997).  The effects of vegetation on longitudinal dispersion.   Estuarine, Coastal & Shelf Science, 44: 675-684.
Abstract

Nepf, H. and C. Oldham (1997).  Exchange dynamics of a shallow contaminated wetland  , Aquatic Sciences,59: 193-213.
Abstract

Nepf, H., J. Sullivan, and R. Zavistoski (1997).  A model for diffusion within emergent vegetation,   Limn. Oceanogr.,42(8): 85-95.
Abstract

Geyer, W.R. and H. Nepf. 1996. Tidal pumping of salt in a moderately stratified estuary. Coastal and Estuarine Studies, 53: 213-226.

Nepf, H. and W.R. Geyer. 1996. Intra-tidal variations in stratification and mixing in the Hudson Estuary. J.Geophys. Res., 101: 12,079-12,086.
The Article

Nepf, H., E. Cowen, S. Kimmel, and S. Monismith. 1995. Longitudinal vortices beneath breaking waves. J. Geophys. Res., 100: 16,211-16,221.
Abstract

Nepf, H. and S. Monismith. 1994. Wave dispersion on a sheared current. Applied Ocean Research, 16: 313-316.

Nepf, H. and S. Monismith. 1991. An experimental study of wave-induced- longitudinal vortices. J. of Hydraulic Engineering, 117: 1639-1649.
Abstract

Monismith, S., J. Koseff, J. Thompson, C. O'Riordan, Ý and H. Nepf. 1990. A study of model bivalve siphonal currents. Limn. & Ocean. 35: 680-696.
Abstract

 

CEE / Parsons Lab / MIT