Rock Chute Design

This Excel spreadsheet is included as a tool to design rock chutes for conservation practices. Median size for rock is determined along with the chute hydraulics and dimensions. This spreadsheet is based on "Design of Rock Chutes" by Robinson, Rice, and Kadavy, ASAE Vol. 41(3), pp. 621-626, 1998. One Spreadsheet version is included. Rock_Chute.xls is intended for Excel in Microsoft Office 97. The program was developed by the Iowa design staffa nd modified by the WI-engineering staff. The Excel file (.xls) is password protected. A Glossary is included.

Rock chute design information is consolidated from several sources to provide a comprehensive design tool. The rock slope stability, boundary roughness, and outlet stability of rock chutes are each discussed. Tests were performed in three rectangular flumes and in two full size structures. Angular riprap with a median stone size ranging from 15 to 278 mm was examined on rock chutes with slopes ranging from 2 to 40%. The typical mode of channel failure is described. An empirical prediction equation is presented relating the highest stable discharge on a rock chute to the median stone size and the bed slope. A boundary roughness relationship is also presented that relates the Manning roughness coefficient to the median stone size and bed slope. These tests also suggest that the riprap size required for stability on the slope will remain stable in the outlet reach even with minimal tailwater. This article contains information needed to perform a rock chute design. Rock chutes or loose-riprap-lined channels are used to safely convey water to a lower elevation. These structures provide an alternative method of protecting the soil surface to maintain a stable slope and to dissipate a portion of the flow energy. Watershed management applications for this type of structure are numerous such as channel stabilization, grade control, and embankment overtopping. Depending on the availability and quality of accessible rock materials, rock chutes may offer economic advantages over more traditional structures. Flow cascading down a rock chute is visually pleasing, and these structures offer aesthetic advantages for sensitive locations. Construction of these chutes can be performed with unskilled labor and a comparatively small amount of equipment. A typical rock chute profile is shown in figure 1.

• Resource Title: Rock Chute Design Data spreadsheet.

  File Name: nrcs142p2_024307.xls

  Resource Description: Local copy of the spreadsheet tool.

  The user should refer to the Rock Chute Design - Plan Sheet for print buttons. The user should not print with the print icons (standard icons) or menus in Excel, not all the design information will print. This is the major input area for setting channel geometry. All red, italicized values and text can be entered (or changed) by the user.