Erosion can be both helpful and harmful. 

It benefits people by contributing to the formation of soil through the breaking up of rock. It causes rich soil to be deposited on valley floors and at the mouth of rivers. Erosion also has produced some of the world's most spectacular geological formations. The Grand Canyon in the United States, for instance, has been created over the course of millions of years by erosion from the Colorado River.

                                         Pictures of the Grand Canyon, United States of America

One of the most harmful effects of erosion is that it robs farmland of productive topsoil. For this reason, it is one of the leading threats to the food supply. Erosion can also wash valuable fertilizers from farmland and carry pollution-causing agricultural chemicals into lakes and rivers. Eroded soil can clog irrigation ditches, ponds, and reservoirs. Gullies caused by flowing water may ruin fields by making them too small to farm with tractors and other modern equipment.