Project Record Item #2. Structure Descriptions Total of (4) different types of structures will be used for sediment retention techniques:

1. Media Lunas (Flow spreaders/collectors) 2. One-rock Dams (Grade control) 3. Loose rock check dams (Gully plugs) 4. Zuni bowls (Headcut repair)

1. MEDIA LUNA

Medina Luna structures are used to manage sheet flow and prevent erosion. These “sheet flow spreaders” will be used in areas that are on relatively flat ground to disperse erosive channelized flow and reestablish sheet flow where it once occurred. This type of structure will comprise of appropriately sized rocks, generally 4-10” . They will be placed in formations one rock tall with the bottom row acting as a footer, dug in, and subsequent rows offsetting the previous row. This would provide a good locking structure that will capture sediment and provide germination sites for native plants.

2. ONE-ROCK DAMS

One-rock dams are small grade control and flow slowing structures that are only one rock high. The dams would be built with several rows of rock across from the up-stream to the downstream edge. They will be no taller than 1/3 bankfull depth of the channel. Stones would be selected, sized and placed so that the completed structure ends up relatively level from bank to bank and flat from the upstream edge to the downstream edge. This is accomplished by placing larger rocks in the deepest part of the channel and as a footer row, and then similar ones to either side. Rocks will not be stacked on top of one another, due to the possibilities of them being swept away from flood flows. Placing greatly oversized rocks in the structure will generate turbulence that could undermine it. Flood flows will pack smaller-sized bedload particles between the rocks, gradually strenghtening the structure over time as new vegetation begins to develop at the site.

3. LOOSE ROCK CHECK DAMS

Loose rock check dams would be constructed across the gully beds to stop channel and lateral erosion. The sides of the check dams will be constructed higher than the center so that water is always directed over the center of the dam. Indirectly, this avoids the dam being outflanked by the flow of water. By reducing the original gradient of the gully channel, check dams diminish the velocity of water flow and the erosive power of run-off. Run-off during peak flow is conveyed safely by check dams. Temporary check dams, which have a life span of three to eight years, collect and hold soil and moisture in the bottom of the gully. Tree seedlings, as well as shrub and grass cuttings planted in gullies, can grow without being washed away by flowing water. Thus, a permanent vegetation cover can be established in a short timeframe.

4. ZUNI BOWLS

Zuni bowls are a headcut control structure composed of rock lined step falls and plunge pools that prevents headcuts from continuing to migrate upstream. Zuni Bowls would be use to stabilize actively eroding headcuts by dissipating the energy of falling water at the headcut pour over and the bed of the channel. The structure converts the single cascade of an eroding headcut into a series of smaller step falls. Zuni Bowls also serve to maintain soil moisture on the face of the headcut, encouraging the establishement of protective vegetation.