tailieunhanh - ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - SEDIMENT TRANSPORT AND EROSION

Trầm tích và xói mòn GIAO THÔNG VẬN TẢI GIỚI THIỆU Các tài liệu về chủ đề của sự xói mòn và vận chuyển trầm tích rộng lớn và được xử lý trong các ấn phẩm của các ngành như kỹ thuật dân sự, khoa học đất, nông nghiệp, địa lý và địa chất. Bài viết này cung cấp một giới thiệu ngắn gọn cho các đối tượng xói mòn đất, vận chuyển các mảnh vụn bởi các dòng và phản ứng của một kênh dòng để thay đổi về đặc tính trầm tích của nó. Người làm ruộng là có. | S SEDIMENT TRANSPORT AND EROSION INTRODUCTION The literature on the subject of erosion and sediment transport is vast and is treated in the publication of such disciplines as civil engineering soil science agriculture geography and geology. This article provides a brief introduction to the subjects of soil erosion transport of detritus by streams and the response of a stream channel to changes in its sediment characteristics. The agriculturalist is concerned with the loss of fertile land through erosion. Sheet gully and other erosion mechanisms result in the annual movement of about five billion tons of sediment in the United By this process plant nutrients and humus are washed away and conveyed to the streams reservoirs and lakes. The sediment characteristics of a stream also affect its aquatic life. Changes in the character of the sediment load will normally tend to change the balance of aquatic life. Fine sediment derived from sheet erosion causes turbidity in the waterways. This turbidity may interfere with photosynthesis and with the feeding habits of certain fish thus favoring the less susceptible often less desirable varieties of fish. The resulting mud deposits may have similar selective results on spawning. The plant nutrients phosphates and nitrates that accompany erosion from farmlands may contribute to the eutrophocation of the receiving waters. Turbidity also makes waters less desirable for municipal and industrial use. Mud deposits may ruin sand beaches for recreational use. From the engineer s point of view an understanding of sediment transport processes is essential for proper design of most hydraulic works. For example the construction of dam on a stream is almost always accompanied by a reservoir siltation or aggradation problem and a degradation problem. A reasonable prediction of the rate of reservoir siltation is necessary in order to establish the probable useful life and thus the economics of a proposed reservoir. The degradation or