Hazardous MetropolisFlooding and Urban Ecology in Los Angeles

Orsi, Jared

doi:10.1525/california/9780520238503.001.0001

Cited by 14 publications

(4 citation statements)

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“…The PRIMo model has also been qualitatively validated with comparisons to other local models (Sanders et al., 2023) and feedback from stakeholders (Ulibarri et al., 2023). Furthermore, PRIMo predictions align with past studies documenting the Black, Hispanic, and disadvantaged communities at risk along main‐stem flood channels and in the lower watershed, especially (Orsi, 2004). Nevertheless, the degree of validation could be improved, and there remains an urgent need, as well as a challenge, to validate urban flood models nationwide and globally as others have suggested previously (Bates, 2012, 2023a; De Moel et al., 2015; Jonkman, 2013; Molinari et al., 2019; Trigg et al., 2016).…”

Section: Discussionsupporting

confidence: 82%

National‐Scale Flood Hazard Data Unfit for Urban Risk Management

Schubert,

Mach,

Sanders

2024

Earth's Future

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Extreme flooding events are becoming more frequent and costly, and impacts have been concentrated in cities where exposure and vulnerability are both heightened. To manage risks, governments, the private sector, and households now rely on flood hazard data from national‐scale models that lack accuracy in urban areas due to unresolved drainage processes and infrastructure. Here we assess the uncertainties of First Street Foundation (FSF) flood hazard data, available across the U.S., using a new model (PRIMo‐Drain) that resolves drainage infrastructure and fine resolution drainage dynamics. Using the case of Los Angeles, California, we find that FSF and PRIMo‐Drain estimates of population and property value exposed to 1%‐ and 5%‐annual‐chance hazards diverge at finer scales of governance, for example, by 4‐ to 18‐fold at the municipal scale. FSF and PRIMo‐Drain data often predict opposite patterns of exposure inequality across social groups (e.g., Black, White, Disadvantaged). Further, at the county scale, we compute a Model Agreement Index of only 24%—a ∼1 in 4 chance of models agreeing upon which properties are at risk. Collectively, these differences point to limited capacity of FSF data to confidently assess which municipalities, social groups, and individual properties are at risk of flooding within urban areas. These results caution that national‐scale model data at present may misinform urban flood risk strategies and lead to maladaptation, underscoring the importance of refined and validated urban models.

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Section: Discussionsupporting

confidence: 82%

National‐Scale Flood Hazard Data Unfit for Urban Risk Management

Schubert,

Mach,

Sanders

2024

Earth's Future

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“…These natural hydrologic processes have been altered since the early 1940s, as the growing human population of southern California led to the construction of flood control infrastructure to avoid loss of life and property (Orsi, 2004). Some of the most heavily modified habitats include estuaries, lakes, and streams, with non-native predatory fish species thriving where these habitats have either been created or altered from their natural state (Power, 1990;Moyle and Marchetti, 2006;Francis and Chadwick, 2012).…”

Section: Effects Of Novel Ecological Disturbance On Native Fauna and Floramentioning

confidence: 99%

“…Without controlled discharge from reservoirs or other upstream areas, these drainages would largely dry out during the latter parts of the year. Tappe and Grinnell were surely referring to habitat prior to a time when this infrastructure existed, as major construction began only in the early 1940s (Orsi, 2004). In fact, beaver were unable to persist at sites in upper San Mateo Creek, San Diego County following releases in 1947 because surface water was too sporadic, forcing them to move ∼32 km downstream to the lagoon at the mouth of the creek (Ervin, 2017).…”

Section: Indigenous Evaluation Of the Ecosystem Engineer-how Strong Is The Evidence?mentioning

confidence: 99%

Impacts of a Non-indigenous Ecosystem Engineer, the American Beaver (Castor canadensis), in a Biodiversity Hotspot

Richmond

Swift

Wake³

et al. 2021

Front. Conserv. Sci.

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Non-native species having high per capita impacts in invaded communities are those that modulate resource availability and alter disturbance regimes in ways that are biologically incompatible with the native biota. In areas where it has been introduced by humans, American beaver (Castor canadensis) is an iconic example of such species due to its capacity to alter trophic dynamics of entire ecosystems and create new invasional pathways for other non-native species. The species is problematic in several watersheds within the Southern California-Northern Baja California Coast Ecoregion, a recognized hotspot of biodiversity, due to its ability to modify habitat in ways that favor invasive predators and competitors over the region's native species and habitat. Beaver was deliberately introduced across California in the mid-1900s and generally accepted as non-native to the region up to the early 2000s; however, articles promoting the idea that beaver may be a natural resident have gained traction in recent years, due in large part to the species' charismatic nature rather than by presentation of sound evidence. Here, we discuss the problems associated with beaver disturbance and its effects on conserving the region's native fauna and flora. We refute arguments underlying the claim that beaver is native to the region, and review paleontological, zooarchaeological, and historical survey data from renowned field biologists and naturalists over the past ~160 years to show that no evidence exists that beaver arrived by any means other than deliberate human introduction. Managing this ecosystem engineer has potential to reduce the richness and abundance of other non-native species because the novel, engineered habitat now supporting these species would diminish in beaver-occupied watersheds. At the same time, hydrologic functionality would shift toward more natural, ephemeral conditions that favor the regions' native species while suppressing the dominance of the most insidious invaders.

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“…Habitats were diminished due to most of the L.A. River bottom being impervious concrete [15]. One of the key aspects of the paved condition is the decrease in plant life, which would absorb excess nitrogen in the environment through its roots.…”

Section: Introductionmentioning

confidence: 99%

The Community Structure of eDNA in the Los Angeles River Reveals an Altered Nitrogen Cycle at Impervious Sites

et al. 2023

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In this study, we sought to investigate the impact of urbanization, the presence of concrete river bottoms, and nutrient pollution on microbial communities along the L.A. River. Six molecular markers were evaluated for the identification of bacteria, plants, fungi, fish, and invertebrates in 90 samples. PCA (principal components analysis) was used along with PAM (partitioning around medoids) clustering to reveal community structure, and an NB (negative binomial) model in DESeq2 was used for differential abundance analysis. PCA and factor analysis exposed the main axes of variation but were sensitive to outliers. The differential abundance of Proteobacteria was associated with soft-bottom sites, and there was an apparent balance in the abundance of bacteria responsible for nitrogen cycling. Nitrogen cycling was explained via ammonia-oxidizing archaea; the complete ammonia oxidizers, Nitrospira sp.; nitrate-reducing bacteria, Marmoricola sp.; and nitrogen-fixing bacteria Devosia sp., which were differentially abundant at soft-bottom sites (p adj < 0.002). In contrast, the differential abundance of several cyanobacteria and other anoxygenic phototrophs was associated with the impervious sites, which suggested the accumulation of excess nitrogen. The soft-bottom sites tended to be represented by a differential abundance of aerobes, whereas the concrete-associated species tended to be alkaliphilic, saliniphilic, calciphilic, sulfate dependent, and anaerobic. In the Glendale Narrows, downstream from multiple water reclamation plants, there was a differential abundance of cyanobacteria and algae; however, indicator species for low nutrient environments and ammonia-abundance were also present. There was a differential abundance of ascomycetes associated with Arroyo Seco and a differential abundance of Scenedesmaceae green algae and cyanobacteria in Maywood, as seen in the analysis that compared suburban with urban river communities. The proportion of Ascomycota to Basidiomycota within the L.A. River differed from the expected proportion based on published worldwide freshwater and river 18S data; the shift in community structure was most likely associated with the extremes of urbanization. This study indicates that extreme urbanization can result in the overrepresentation of cyanobacterial species that could cause reductions in water quality and safety.

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Hazardous MetropolisFlooding and Urban Ecology in Los Angeles

Cited by 14 publications

References 0 publications

National‐Scale Flood Hazard Data Unfit for Urban Risk Management

National‐Scale Flood Hazard Data Unfit for Urban Risk Management

Impacts of a Non-indigenous Ecosystem Engineer, the American Beaver (Castor canadensis), in a Biodiversity Hotspot

The Community Structure of eDNA in the Los Angeles River Reveals an Altered Nitrogen Cycle at Impervious Sites

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