References
================

[1] `Frank Engelund: Flow and Bed Topography in Channel Bends, 
Journal of the Hydraulics Division, 1974, Vol. 100, Issue 11, Pg. 1631-1648
<https://cedb.asce.org/CEDBsearch/record.jsp?dockey=0022331>`_ 

[2] `Yasu Shimizu, Equations used in Nasy2d+ solver in iRIC 
<https://i-ric.org/yasu/refs/SecondaryFlowEqs_EN.pdf>`_