The Future of Sediment Transport and Streamflow Under a Changing Climate and the Implications for Long‐Term Resilience of the San Francisco Bay‐Delta

Abstract

Sedimentation and turbidity have effects on habitat suitability in the San Francisco Bay-Delta (Bay-Delta), concerning key species in the bay as well as the ability of the delta marshes to keep pace with sea level rise. A daily rainfall runoff and transport model of the Sacramento River Basin of northern California was developed to simulate streamflow and suspended sediment transport to the Bay-Delta for the next century (water years, WY2010-2099). The model was calibrated to historical streamflow and sediment data and applied using 10 Global Climate Models with two representative concentration pathways (RCP) each for WY1980-2099 from the IPCC 5th Assessment Report. Results indicate average increases in peak streamflow of +58% and +66% for the RCP 4.5 and 8.5 ensembles, respectively, by mid-century and +62 and +96% by end-of-century. Sediment loads increased by +39% and +69% by end-of-century. Suspended sediment concentrations (SSC) increased on average by +4.6% and +6.7% for RCP 4.5 and 8.5, respectively, by end-of-century. Individual scenario results varied, and statistically significant increasing trends of sediment loads to the Bay-Delta were found for the RCP 4.5 and 8.5 ensembles and five individual scenarios. Increased suspended sediment loads may have negative effects such as contaminant transport but also have positive effects that help protect against sea level rise, increase turbidity and fish habitat, and sustain wetland habitats in the Bay-Delta. Plain Language Summary The health of the San Francisco Bay-Delta depends on a sediment supply that has been recently declining. Future climate scenarios were run through a model to determine changes in streamflow and sediment transport. Results from the model showed increases in large flow events and sediment transport over the next century. Increased sediment supply can help buffer wetland habitats against the deleterious effects of sea level rise with benefits to native fishes.

Multi-objective Allocation Optimization of Soil Conservation Measures Under Data Uncertainty

“…We only consider the detachment of material but not the transport and deposition, which may have additional effects, such as contaminant transport (He et al, 2009 ). Sediment yields from soil erosion (Endalew and Biru, 2022 ) can be even beneficial under specific circumstances (Stern et al, 2020 ). If certain areas are too steep to be cultivated or used for other purposes, the lost soil is less critical.…”

Incorporation of uncertainty to improve projections of tidal wetland elevation and carbon accumulation with sea-level rise

“…Lower total precipitation and associated fluvial discharge projected in the future [ 84 ] points to a probable reduction in sediment supply to the estuary. However, high fluvial discharge from more intense atmospheric rivers [ 85 ] and rain-on-snow weather events [ 86 , 87 ] could bolster sediment supplies [ 46 ], especially as watersheds continue to become urbanized downstream of dams and reservoirs [ 88 ]. Sediment may become a more limited resource for wetlands across San Francisco Bay-Delta as tides deliver sediment to new expansive restoration projects [ 50 ]; however a bay-wide sediment budget is not yet available.…”

“…The historic, constant, and declining scenarios are based upon the projections in Cloern et al [ 45 ]; the historic scenario used the coefficient derived from the soil core calibration and is representative of the sediment available ( C ) over the last century ( Table 1 ), the constant scenario assumed future C will only be 60% of historic conditions, and the declining scenario assumed a 1.6% annual decrease in C from the constant scenario. The increased sediment supply scenario was conceptually based upon the potential for a wetter future due to climate change, as well as continued land cover changes within the watershed, and assumed a 25% increase in C over the historic scenario [ 46 ].…”

“…Wetland elevation models are often developed and parameterized for specific geographic regions or well-studied plant species (usually Spartina alterniflora in USA), and the transferability of such parameters to other wetlands is unknown. Many modeling efforts also do not incorporate plant community change over time, even though it is well documented that tidal wetland vegetation composition can vary markedly with elevation, inundation, and salinity [ 43 , 44 ], and that climate change is projected to alter both flooding and salinity gradients in estuaries [ 45 , 46 ]. Simulations of wetland carbon storage range from relatively simple accounting approaches [ 47 ] to more complex biochemical models [ 48 ].…”

Water pollution generated by tourism: Review of system dynamics models

“…Additionally, the expansion of tourism infrastructure, including the construction of hotels, roads, and ports, can lead to habitat destruction and increased sedimentation in water bodies [ 12 ]. Construction activities introduce pollutants such as sediment, heavy metals, and chemicals into aquatic ecosystems, causing long-term damage.…”