Small Stream Channel Dam Aeration Characteristics

Abstract

Field data were collected at 54 small stream head loss structures in northeastern Illinois to evaluate weir and spillway aeration characteristics. The British dam aeration equation, which employs the use of an aeration coefficient (b), is used as a model to calibrate each head loss structure. The head loss structures are categorized according to basic physical configurations; nine generalized classes are presented. The aeration coefficients vary widely within classes due to seemingly small or subtle differences in structural design or overall physical condition. Spillways having the same basic geometric design may exhibit widely divergent aeration coefficients depending upon conditions at the toe or apron. Hydraulic jumps built into toes produce significantly higher b‐values than those similarly constructed but without hydraulic jumps. The nine dam categories are assigned aeration coefficients which represent the median value observed within each grouping. These values are suitable for use in preliminary model development or when time constraints preclude making field surveys. However, whenever possible field surveys should be conducted using the methodology presented as a guide.