| Abstract: | The purpose of this study is to investigate the effect of overloading on bedforms, resistance to flow, sediment transport rate and average bed profile of aggrading by overload. A series of aggradation experiments were carried out by overfeeding sediment load to a movable bed channel previously maintained in equilibrium. The bed and water surface profiles were recorded and the sediment transport rate was measured. These data were used to i) study the time evolution of bedforms and resistance to flow during the transient situation generated by overloading; to ii) check the applicability of the sediment transport model suggested by Yen et al. to the non equilibrium sediment transport data; and iii) to test the version of the linear parabolic model suggested by Jain for describing aggrading bed profiles. The dimensions of bedforms decrease due to overloading while their celerity increase; Manning's coefficient n was also observed to increase. In the sequence of the analysis of the sediment transport data, a slightly different version of the model of Yen et al. is suggested and a new relation for the calculation of the velocity of the deposition front is proposed. The linear parabolic model was seen to properly describe the bed trend of aggrading profiles for overloading ratios equal or greater than 4. |
