250 



A rise in sea level results in an increase in depth and an 

 increase/decrease in the ocean tidal range and indirectly through the 

 mixing processes affects the density gradients. We have a reasonable 

 understanding as to how external forcings and bathjnnetry affect residual 

 currents and mixing processes in a qualitative sense. For quantitative 

 realistic estimates, our present knowledge of especially turbulent exchange 

 processes of mass and momentum in the presence of stratification is too 

 limited. Therefore, any estimate of the effect of sea level rise on 

 transport processes/salt intrusion in an estuary has to be of a qualitative 

 nature ! 



Following are a few examples as to how residual currents and mixing 

 are affected. 



Classical estuarine circulation (= gravitational circulation) . 



u = -2 .^ (A. 7) 



p ax N2 



where u = velocity, g = gravity acceleration, p = density of water, x = 

 longitudinal coordinate, h = depth, and N2 = coefficient for turbulent 

 vertical exchange of momentum. Note the dependence of u on h-* . The 

 longitudinal dispersion coefficient, D, associated with gravitational 

 circulation is 



D :: 



g 3p 



I p ax J 



^^^h5 (A.8) 



Ni ^- 



where K2 = coefficient for turbulent vertical exchange of mass. Note the 

 dependence of D on h-' . 



Horizontal residual currents driven by longitudinal density gradients: 



u::|! (A.9) 



