General description

During the calculation of coastline evolution, the transport rates are found by interpolation in the tables rather than calculating each transport rate directly. The tables contain the transport rates for given conditions at the line of wave breaking (Breaking point).

The tables are generated by successive calls to the littoral drift model engine, and input includes the usual input to Littoral drift. The varying hydrodynamic parameters are specified by the minimum and the maximum value, valid for the first grid point in the profile, and the number of different values occurring in the table. The table may contain different cross-shore profiles as well.

Based on the input, the total transport rates Q_t (I_g,wl,T,h_b,ab,i) as well as the cross-shore distribution Q_d (I_g,wl,T,h_b,ab) are tabulated for an envelope of the hydrodynamic and bathymetric conditions. The maximum dimensions for the various parameters describing a table is given in Table 5.1 below.

Table 5.1 List of parameters to describe a LITLINE table
Name	Description	Max. number of values
i_g:	Slope of water surface due to regional current	9
wl:	Water level	25
T:	Wave period	25
h_b:	Wave height at breaking point	25
ab:	Incoming wave angle at breaking point	25
i:	Cross-shore profile (cross-section number)	8

The tables are specified by a Global name “name” which is common for all the files that combined represent one table. A transport table for coastline evolution consists of four different types of files.

Table 5.2 List of files contained in a LITLINE table
File name	Description
name.val	This file (ASCII format) contains information about the parameters related to the transport rates in the tables.
nameqtt.i	This file (binary format) contains the total sediment transport rates for cross-section no. i along the coastline
nameqtd.i0j	This file (binary format) contains the distributed sediment transport rates across the profile for cross-section no. i and surface slope no. j
namenqd.i0j	This file (binary format) contains the positions of the distributed sediment transport rates across the profile for cross-section no. i and surface slope no. j

Some combinations of I_g,wl,T,h_b and a_b cannot exist for the given bathymetric conditions. In these cases the sediment transport rate will be given a very small default value below 10^-7 m³/s.