Gully plug (Jourdan)

Authors: HADDAD, MIRA - International Centre For Agricultural Research In The Dry Areas (ICARDA); VERBIST, JOREN - International Centre For Agricultural Research In The Dry Areas (ICARDA); STROHMEIER, STEFAN - International Centre For Agricultural Research In The Dry Areas (ICARDA); Evett, Steven - Steve

Submitted to: World Overview of Conservation Approaches and Technologies (WOCAT) Global Database on Sustainable Land
Publication Type: Database / Dataset
Publication Acceptance Date: 3/18/2021
Publication Date: 3/29/2021
Citation: Haddad, M., Verbist, J., Strohmeier, S., Evett, S.R. 2021. Gully plug (Jourdan). United Nations Convention to Combat Desertification. World Overview of Conservation Approaches and Technologies (WOCAT) Global Database on Sustainable Land Management (SLM). Online: United Nations Convention to Combat Desertification. Technologies article 5862. https://qcat.wocat.net/en/wocat/technologies/view/technologies_5862/.

Interpretive Summary: Rangeland rehabilitation can be required due to erosion resulting from rainfall and runoff after land degradation caused by overgrazing, fire, and climate change. In severe cases of erosion, large gullies are formed that, if not remediated, become ever larger and deeper and cause increased erosion of surrounding areas as well as lowering of local water tables. This results in decreased water availability for vegetation, which leads to decreased vegetative cover and even more erosion. Stopping this cycle of land degradation can be aided by installation of gully plugs, but proper design and construction are key to success. A team of USDA ARS and ICARDA scientists and engineers cooperated to produce a rock gully plug design guide based on field installation and multi-year testing of 55 gully plugs in an arid rangeland. The gully plugs, built of locally sourced rock, were shown to slow flood flows, and trap sediments and water, which provided fertile locations for vegetation to take hold within the gullies. The enhanced vegetation further trapped sediments, which gradually filled the gullies, reducing the erosive potential on surrounding rangeland and improving overall plant water availability and range productivity.

Technical Abstract: Gully plugs aim at rehabilitating active gullies in dryland watersheds, which are prone to erosion through concentrated surface runoff. Multiple gully plugs in succession dissipate runoff energy, foster local water retention and infiltration, encourage sedimentation, assist in the stabilization of gully bed and side banks, and stimulate revegetation of flow paths; the channel measures must be combined with proper sustainable land management in the catchment upstream. Multiple gully plugs positioned sequentially within a gully system interrupt concentrated surface runoff and reduce its erosive power. The plugs are each made of multiple cobbles/stones mostly ranging between 10 and 30 cm diameter and constructed to ensure a stable structure. The plugs started at the head of the gully (upstream) and range from 1.5 - 3.7 m in width with an average of 2.5 m. For heavily eroded and very unstable sections, gabions can be used also. The structures are around 1.0 to 1.5-m high, anchored into the sidewalls, and around 0.20 to 0.35 m deep into the gully bed, built up to around 1/3 to max. 1/2 of the gully depth - ensuring the concentrated flow stays within the channel and does not overflow the side banks. The top of the plug is U-shaped, with the sides built higher than the centre. Upslope, the plugs are packed with soil to trap sediments (stopping it flowing through the structure), and downslope the plugs have an apron to dissipate the energy of overflowing water, into a micro stilling basin. The downslope side of the gully plug is sloped rather than vertical. The large stones add roughness to the slope, creating a rough spillway that dissipates erosive energy. In the direction of gully flow, several gully plugs are placed such that the upper gully apron is set at approximately the height of the following downstream gully crest.