1 With quantitative thalweg evolution analysis in rivers coordinate system, the accurate thalweg of planar and vertical displacement of erosion and deposition can be calculated.

2 The thalweg in loess hill area is an important terrain structural line, reflecting topography and landform character.

3 The study shows that the technology and method of distilling the thalweg using DEM are practical and effective.

4 Raster DEM grid search method is to obtain the riverbed thalweg through a two-dimensional matrix search with a certain height rules.

5 The effects of permeable pile groynes laid out along the thalweg in control and guide the regime of the lower Yellow River have been studied through movable bed model tests.