Author(s): G. Aron, C. McIntyre, J. H. Willenbrock

On May 7, 1992, the Advisory Council to the Pennsylvania Housing Research Center authorized additional monies to be spent on further research in the area of storm water management focusing on alternative methods. The score of this research effort focused on flow through large-size porous media, in essence angular limestone rock typically used in the construction of gabions. The ultimate goal of this study was to develop a design equation for gabion dams used to store and release storm water runoff at prescribed discharge rates from a detention basin.

A series of laboratory gradation and flow tests was conducted on angular limestone rock. Results of these measurements were applied to mathematical relationships which were modified to fit the observed data. A gabion design equation was developed, which is a function of rock diameter, horizontal flow path length, ponding depth in the basin, and gabion dam width. The design equation was checked against the observed values, and then used in a routing sequence in a sample detention basin. The design and routing results yielded reasonable values using a gabion dam as the storage and release mechanism.

A gabion dam may prove to be an attractive alternative to conventional storm water management detention and outlet works. In heavily wooded sites or where excess fill is not available for the construction of traditional dikes, gabions may be the most cost-effective means of controlling storm runoff. A gabion dam inherently constitutes its own spillway or discharges the collected runoff as shallow overland flow, thus also acting as an energy dissipating device.

Hopefully, some engineering design firm, in conjunction with the owner/developer, will apply the information in this report to an actual site. In other words, construct a gabion dam to be used as an integral part of a storm water management system in a residential development.