Evidence of the impact of urbanization on the hydrological regime of a medium-sized periurban catchment in France

Abstract

International audienceIn this paper we explore several indicators to evidence the impact of land use change, and particularly of urbanization/artificialization on discharge series of periurban catchments. A first set of indicators is derived from the literature and describes the monthly and annual hydrological regime, low flows and high flows, and flow components. Statistical tests are also applied to assess the existence of trends/rup-tures on the longest time series. In addition, new indicators, especially built to show the impact of sewer overflow devices (SODs) and infiltration into sewer networks are proposed. The method is applied to the Yzeron (150 km 2) catchment, located close to Lyon city (France) where various discharge gauges with a variable time step are available on sub-catchments ranging from a few to 130 km 2 (some of them nested), with a large variety of land uses (forest, agricultural land, artificialized areas). In addition, discharge is also measured in a SOD and a combined sewer network so that the relevance of the new proposed indicators can be assessed. In the largest sub-catchments, the results show a decrease of specific discharge from upstream to downstream corresponding to an increase of artificialized areas, except for high flows. When a SOD is present, the specific discharge is increased for frequencies larger than 50%, and the frequency of zero daily discharge is decreased. Waste water can be the only source of water in autumn month in a 4.1 km 2 sub-catchment. Base flow is also decreased for the most urbanized catchments. Our results confirm the impact of SODs on the modification of the flood regime, with an increase of frequent floods, but a marginal impact on the largest floods, mainly governed by saturation of the rural parts of the catchments. The decomposition of the sewer discharge shows that, on an annual basis, infiltration in the sewer network accounts for 30% of the total discharge and runoff due to rainwater to about 40% (the remaining being composed of the waste water discharge). It can explain the decrease of base flow. Our analysis shows that, for periurban catchments, a long term monitoring of nested sub-catchments and infrastructures (SODs, sewer networks) with a small time step, is very valuable and provides data allowing a quantitative assessment of the impact of urbanization on the whole hydrological regime

Diagnóstico preliminar da integridade ambiental de fundos de vale

“…Essas mudanças têm impactos nos ecossistemas aquáticos e sobre o ciclo da água, devido ao aumento e à aceleração do escoamento superficial, à diminuição da recarga de águas subterrâneas, à modificação das vias naturais de escoamento da água devido às canalizações, dentre outros (BRAUD et al, 2013).…”

“…Foram selecionados da literatura e da legislação nacional indicadores que pudessem avaliar a condição ambiental de áreas de fundo de vale (BRASIL, 2007;2012;BRAUD et al, 2013;CHU et al, 2013;CUSHMAN & GAFFNEY, 2010;HERZOG & ROSA, 2010;RIBEIRO & HELLER, 2004).…”

Impact of urbanization on groundwater in central basin of Hyderabad, Telangana State - India

“…Due to spatial and temporal variations in water chemistry a monitoring programme that will be provide a representative and reliable estimations is necessary [6]. Recent work by Braud et al [7] based on relatively long-term observations, confirms that many of the accepted theories regarding urbanization are evident in the changing hydrological regime of a selected peri-urban area, such as reduced baseflow and reduced lag-times resulting in more 'flashy' flood hydrographs from urban areas.…”

Urban stormwater source control policies: why and how?

“…Leopold 1964): the creation of large impervious, non-vegetated areas associated to urbanization reduces infiltration and evapotranspiration processes, increasing the volume of surface runoff; the efficiency of artificial drainage systems reduces concentration times during rainfall and concurs, with the increased runoff volumes, to increase peak flow-rates. But the extent and consequences of these relatively simple processes are still the object of research (Walsh et al 2005, Braud et al 2013.…”