An Overview of a Two Dimensional Hydraulic Modeling of Llano Seco Riparian Sanctuary on Sacramento River

Llano Seco riparian sanctuary is located near River Mile (RM) 177 of the Sacramento River, on the eastern floodplain of the river. This particular section of the Sacramento River has a natural overflow which discharges into the Butte Basin to the southeast. The flood control levee on the east side of the river begins near the downstream end of the model (approximately at RM 176). The floodplain on the west bank of the river in the project reach is controlled by a levee, which begins upstream at approximate RM 184. The restoration area is located adjacent to the river, on the east side, between RM 177 and RM 178. In previous years riparian growth was on the majority of this area, documented in the historic 1952 and 1974 aerial images. The riparian growth was almost entirely removed (except a small section adjacent to the river at the top of the bend) at some time after 1974. It has been proposed to convert approximately 350 acres of grassland/savannah to riparian habitat. A two-dimensional (2D) hydraulic model of the Sacramento River, from River Mile (RM) 173 to RM 194 was developed and run to assist in this analysis. The resulting water surface elevations were compared to the design water surface elevations developed by the US Army Corps of Engineers (USACE) in 1957 for the Sacramento River Flood Control System.