Effects of Urban Development on Stream Ecosystems in Nine Metropolitan Study Areas Across the United States

U.S. Geological Survey (USGS) | November 13th, 2012

Urban development is an important agent of environmental change in the United States. The urban footprint on the American landscape has expanded during a century and a ha

Urban development is an important agent of environmental change in the United States. The urban footprint on the American landscape has expanded during a century and a half of almost continuous development. Eighty percent of Americans now live in metropolitan areas, and the advantages and challenges of living in these developed areas—convenience, congestion, employment, pollution—are part of the day-to-day realities of most Americans. Nowhere are the environmental changes associated with urban development more evident than in urban streams. Contaminants, habitat destruction, and increasing streamflow flashiness resulting from urban development have been associated with the disruption of biological communities, particularly the loss of sensitive aquatic species. Every stream is connected downstream to larger water bodies, including rivers, reservoirs, and ultimately coastal waters. Inputs of chemical contaminants or sediments at any point along the stream can cause degradation downstream with adverse effects on biological communities and on economically valuable resources, such as fisheries and tourism. In response to general concerns about the degradation of urban streams, the U.S. Geological Survey (USGS) conducted a national-scale, scientific investigation of the effects of urban development on stream ecosystems. Nine metropolitan study areas of the United States were selected—Portland, Oregon; Salt Lake City, Utah; Birmingham, Alabama; Atlanta, Georgia; Raleigh, North Carolina; Boston, Massachusetts; Denver, Colorado; Dallas, Texas; and Milwaukee, Wisconsin. The studies were conducted in Salt Lake City, Birmingham, and Boston in 1999–2000; in Atlanta, Raleigh, and Denver in 2002–2003; and in Portland, Dallas, and Milwaukee in 2003–2004. The comprehensive investigation of all nine studies focused on three broad questions of interest to decision makers: 1. What are the primary effects of urban development on stream ecosystems? 2. How do the effects of urban development on stream ecosystems vary regionally across the country? 3. Which urban-related stressors are most closely linked to biological community degradation, and how can multiple stressors be managed to protect stream health as a watershed becomes increasingly urbanized? RELATED DOCUMENT: Strategies for Managing the Effects of Urban Development on Streams

Effects of vegetation on methylmercury concentrations and loads in a mercury contaminated floodplain

Science of The Total Environment (Elsevier) | August 3rd, 2023

The Yolo Bypass (YB) is a large flood conveyance system designed to protect the city of Sacramento, California, USA from flooding when the Sacramento River approaches flo

The Yolo Bypass (YB) is a large flood conveyance system designed to protect the city of Sacramento, California, USA from flooding when the Sacramento River approaches flood stage. The Sacramento River watershed and YB are a source of methylmercury (MeHg) to downstream habitat as a result of historic mercury (Hg) and gold mining practices. In the dry season, the YB is extensively farmed and grazed. However, depending on the water year, the floodplain may remain inundated for months. Our experiments focused on the role of pasture land and decomposing vegetation as a source of MeHg during extensive periods of floodplain flooding. Decomposing vegetation, rather than sediment, was identified as the principal source of filter passing MeHg (fMeHg) within the floodplain. The decomposing vegetation provided a substrate for microbial methylation of inorganic Hg contained within the plants. In replicated flooded mesocosm experiments, MeHg concentrations increased from 2.78 to 31.0 ng g− 1 dw and 3.41 to 56.8 ng g− 1 dw in decomposing vegetation. In field collections, the concentrations of MeHg in vegetation increased from preflood levels of 2.78 to 45.4 ng g− 1dw after 17 weeks of flooding. The importance of vegetation was shown in laboratory experiments where there was a positive correlation between the amount of fMeHg in water and the amount of vegetation added. These results also provide Hg concentration data for an important functional type of vegetation, grasses, and fill a data gap that contributed to uncertainties with regards to the role of vegetation in Hg cycling.

Effects of water management on the wetlands of the Colorado River Delta, Mexico

Conservation Biology (Society for Conservation Biology) | August 1st, 1996

The lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. No river water is officially appropriated to support de

The lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. No river water is officially appropriated to support delta wetlands, yet large marsh areas of conservation interest still exist below the agricultural fields in Mexico. These are supported by flood water, agricultural drainage water, municipal sewage effluent, and seawater in the intertidal zone. From 1973 to 1993 the area of freshwater and brackish marsh varied widely, from 5800 to 63,000 ha. A new opportunity exists to restore wetlands in the delta now that the upstream water impoundments on the Colorado River are filled and flood flows are once again being directed to the delta. But flood control structures now channel most of the flood water directly to the sea, and most of the effluent waters are deposited in evaporation basins rather than used to support wetlands. If the Yuma Desalting Plant in the United States becomes operational and if the Rio Hardy wetlands continue to be drained, the area of brackish wetlands could decrease to less than 2000 ha in the near future. Preserving the remaining wetlands will require a binational water management plan. The plan should maximize the benefits to wetlands of flood and irrigation return flows that enter the delta, and it should minimize flood risks.

Effects of wildfire on benthic macroinvertebrate assemblages in Southern California streams and implications for bioassessment monitoring programs

California State Water Resources Control Board (SWRCB) | June 13th, 2012

Wildfires are common in arid regions of southern California, sometimes burning as much as half a million acres in a season. These fires often cause dramatic impacts to th

Wildfires are common in arid regions of southern California, sometimes burning as much as half a million acres in a season. These fires often cause dramatic impacts to the vegetation and soils of regional watersheds and, consequently, to the streams that drain them. Water quality programs that monitor and regulate these systems have to account for the influence of these factors upon water quality measurements when making monitoring and regulatory decisions. This is true for traditional water quality measures (nutrients, metals, contaminants, etc.), but is especially important for integrative ecological condition indicators like bioassessment, the use of resident biological communities to infer water quality condition.

Electrical Resistivity Imaging of Seawater Intrusion into the Monterey Bay Aquifer System

National Groundwater Association (NGWA) | June 17th, 2015

We use electrical resistivity tomography to obtain a 6.8‐km electrical resistivity image to a depth of approximately 150 m.b.s.l. along the coast of Monterey Bay. The

We use electrical resistivity tomography to obtain a 6.8‐km electrical resistivity image to a depth of approximately 150 m.b.s.l. along the coast of Monterey Bay. The resulting image is used to determine the subsurface distribution of saltwater‐ and freshwater‐saturated sediments and the geologic controls on fluid distributions in the region. Data acquisition took place over two field seasons in 2011 and 2012. To maximize our ability to image both vertical and horizontal variations in the subsurface, a combination of dipole–dipole, Wenner, Wenner‐gamma, and gradient measurements were made, resulting in a large final dataset of approximately 139,000 data points. The resulting resistivity section extends to a depth of 150 m.b.s.l., and is used, in conjunction with the gamma logs from four coastal monitoring wells to identify four dominant lithologic units. From these data, we are able to infer the existence of a contiguous clay layer in the southern portion of our transect, which prevents downward migration of the saltwater observed in the upper 25 m of the subsurface to the underlying freshwater aquifer. The saltwater and brackish water in the northern portion of the transect introduce the potential for seawater intrusion into the hydraulically connected freshwater aquifer to the south, not just from the ocean, but also laterally from north to south.

Electron bifurcation and fluoride efflux systems implicated in defluorination of perfluorinated unsaturated carboxylic acids by Acetobacterium spp

American Association for the Advancement of Science (AAAS) | July 17th, 2024

Emerging PFAS Trends in Water and Sediment from San Francisco Bay

San Francisco Estuary Institute (SFEI) | August 14th, 2025

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of persistent compounds, including several that are bioaccumulative and known or suspected to be toxic. The

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of persistent compounds, including several that are bioaccumulative and known or suspected to be toxic. These unique compounds have widespread uses across consumer, commercial, and industrial products, resulting in widespread occurrence in humans, the environment, and wildlife across the globe. Within San Francisco Bay, the RMP has monitored PFAS across the Bay ecosystem, beginning in 2004 with various biota and since expanding to sediment, surface water, stormwater, and wastewater. These studies found PFAS throughout the Bay, especially in sport fish, where concentrations are of potential concern for human health and led to a classification of PFAS as High Concern for the Bay under the RMP tiered risk-based framework for emerging contaminants.  This study examined Bay sediment and surface water to continue to build our understanding of the occurrence, fate, and risks of PFAS to ecological and human health. Using a targeted method, 40 PFAS were analyzed in Bay sediment collected in three monitoring cruises from 2017 to 2023, and Bay water collected from 2021 to 2023 during both the dry and wet seasons. The Total Oxidizable Precursor (TOP) assay was also used to supplement these findings by indirectly measuring unknown perfluoroalkyl acid (PFAA) precursors of detectable PFAS. This additional information aids in elucidating the broader levels of PFAS present in samples to better evaluate the exposure and risk to the Bay. 

Emerging understanding of the potential role of seagrass and kelp as an ocean acidification management tool in California

California Ocean Science Trust (OST) | January 2nd, 2018

This report was produced by the OPC-SAT working group and Ocean Science Trust on behalf of the Ocean Protection Council (OPC) and the broader community of California man

This report was produced by the OPC-SAT working group and Ocean Science Trust on behalf of the Ocean Protection Council (OPC) and the broader community of California managers with the aim of: • communicating emerging scientific understanding of the ability of seagrass and macroalgae (kelps) to ameliorate ocean acidification (OA) in a California-specific context, • summarizing knowledge gaps and opportunities for filling them through research and monitoring, and • providing guidance on next steps for the State as it considers future nature-based actions to reduce the negative impacts of OA in California and beyond.

Environment California, Inc. v. City of Los Angeles

Holmes, Athey, Cowan & Mermelstein LLP | July 23rd, 2024

Environmental and anthropogenic drivers of contaminants in agricultural watersheds with implications for land management

Science of the Total Environment (Elsevier) | February 17th, 2021