46 p. fig., tab. Report nr.96.26. - Report in commission of the Ministry of Transport, Public Works and Water Management, Rijkswaterstaat, Institute for Inland Water Management and Waste Water Treatment (RWS, RIZA). - Supervision on behalf of RWS, RIZA: J. de Jonge, J. Botterweg, A. bij de Vaate and A.D. Buijse. - With ref.