Application of The Least Squares Adjustment Method With Conditional Equationsin Calculation of River Dredging Volume

Abstract

One way to handle the silting the river is dredged. To calculate the volume of river dredging, it is required river geometry data that presented in the form of river cross-section pictures and the distance between river cross-section. River cross-section picture obtained from measuremen. Implementation of the cross-section measurements should be conducted in conjunction with the mapping of river situation. Cross section measurement method can be done by tachymetri or echo sounding. Distance used for the calculation of river dredging volume are the average distance between the cross-section on the left bank of the river channel, the distance between the cross-section on the right bank of the river, and the distance between the cross section in the middle of the river channel. The value of the distances are measured on the river situation map. This least squares adjustment method with conditional equations is applied to calculate the volume dredging of Laweyan river. Laweyan river is one of the branches of the Bengawan Solo River estuary. Mathematical models are used as many as 20 models, which is based on relations of the average distance between cross section in each river segment and the average distance between cross sections in every two river segment. From the results can be known, that the large value of distance correction is given on a curved section of river channel and small value given on relatively straight channel. Total volume of dredging of Laweyan river that calculated using the least squares adjustment method is 359,466.689 m3, while the total volume of dredging of river Laweyan that calculated not using the least squares adjustment method is 359.657,001 m3.