Variability in stream ecosystem response to urbanization

Abstract

The geomorphic and ecological degradation of streams resulting from urbanization is well recognized. Recent reviews have hypothesized variability in ecological response to urbanization among stream types and among regions with varying climate and catchment soil and geology. Testing such hypotheses will be aided by the use of consistent metrics of the primary processes that drive urban-induced degradation of streams. We thus developed an urban typology distinguishing the common classes of urban land and water management that are hypothesized to have different effects on stream ecosystems. In developing the typology, we identify and emphasize the importance of step changes (thresholds) in the hydrologic consequences of urbanization, the often-unrecognized massive increase in drainage density of urban catchments, the difficulty in setting reference condition for many cities and the resulting difficulties in comparing responses to urbanization among cities. We critically assess the evidence for variability in responses to urbanization and its causes, and conclude that there are few studies demonstrating intra- or inter-regional differences in response to urbanization that have adequately accounted for the influence of potential differences in urban land and water management. We use the urban typology to propose metrics to allow such accounting, which we argue is necessary to advance management for stream protection and restoration.

The land–river interface: a conceptual framework of environmental process interactions to support sustainable development

“…Changes to land cover in a catchment (e.g. urbanization), regardless of proximity to river channels, can increase peak river discharges, degrade aquatic ecosystems and fisheries resources, cause incision that increases bank erosion, and expose communities in floodplains to increased flood and erosion hazards (Du et al 2015;Roy et al 2016;Booth et al 2016;Vietz et al 2016;Walsh et al 2016). Modifications to valleys, such as dams that impact the land and river directly, cause significant changes to water levels, discharges, sediment flow, and channel form that profoundly affects ecological and human communities along with the river network and further into the terrestrial environment (Richter et al 2010;Beck et al 2012;Kondolf et al 2018;Park et al 2020;Ibisate et al 2013;Aguiar et al 2016;Bejarano et al 2018).…”

“…Even when the urbanization does not directly impact the floodplain or river channel, the connected nature of river systems means that its indirect impacts can perpetuate over long distances (Booth et al 2016;Vietz et al 2016;Walsh et al 2016). Urbanization in the river basin affects the landscape in a multitude of ways.…”

Land Cover and Water Quality Patterns in an Urban River: A Case Study of River Medlock, Greater Manchester, UK

“…Previous studies have recognized impervious covers as predictors of water quality degradation [1,3,5,12]. Generally, water quality degrades when the percentage of impervious cover is more than 10% [3].…”

“…Urbanized areas are often characterized by rapid development, modified or canalized rivers, and a high proportion of impervious land [4,[7][8][9][10][11][12]. Urban land cover, particularly, impervious surface covers which prevent infiltration of water to the soil, include transport systems (roads, parking lots), roof tops and residential development are a key indicator of the environmental impacts of urbanisation [3].…”

“…Urban land cover, particularly, impervious surface covers which prevent infiltration of water to the soil, include transport systems (roads, parking lots), roof tops and residential development are a key indicator of the environmental impacts of urbanisation [3]. Point source pollution collected from impervious urban areas contributes to river flows, changes river hydrology, alters physicochemical processes [13] and degrades assemblages of benthic macroinvertebrates [4,12]. During high flows, combined sewer overflows (CSOs) which collect…”