Water infiltration in urban soils and its effects on the quantity and quality of runoff

Abstract

Purpose Urban soil characteristics, especially soil physical properties, are subject to dramatic changes due to compaction by intensive human activities, which may cause frequent flood events during the rainy seasons. The aim of this study was to explore the water infiltration characteristics of urban soils with different degrees of compaction and to determine the effects of infiltration on environmental problems in urban areas. Materials and methods Ten typical land use patterns with various vegetation and age were selected in Nanjing City, China to determine the infiltration rates by the dual-ring method. Three replicated sites were done in the same combined mode. At the same time, other soil physical and chemical properties that may affect infiltration rate were also determined. In addition, urban surface runoff coefficients were estimated according to final infiltrations and rain intensities in the different degrees of soil compaction. The quality of flood water from a strong rainstorm in a main road in Nanjing was analyzed. Results and discussion The final infiltration rates of urban soils were highly variable (from very slow to very fast). Low soil infiltration rates are related to many factors; however, urban soil compaction is the leading one.Infiltration rates decreased with an increase in the bulk density and with a reduction in the air-filled porosity. Thus, large amounts of macropores increase the infiltration rate and reduce surface runoff. Runoff coefficients of compacted soils with low infiltration rates were high, especially for extremely compacted soil. As a result, the prevalence of flooding is high in compacted soils, and the quality of surface runoff water is reduced during flooding events. The concentrations of NO 3 − -N, total nitrogen, molybdatereactive phosphorus, total phosphors, and suspended material in urban surface runoff were significantly higher than those observed in forested or agricultural watersheds.Conclusions In urban areas, low infiltration rates caused by soil compaction have negative effects on the ecoenvironment of the city and result in increased instantaneous flooding and poor surface water quality. Thus, to improve the eco-environment of urban areas, the amount of greenbelt soil must be increased and soil compaction must be reduced.

Habitat complexity influences fine scale hydrological processes and the incidence of stormwater runoff in managed urban ecosystems

“…Precipitation scenarios (n ¼ 28) were derived from the Intensity-Frequency-Duration rainfall data for the study area (Bureau of Meteorology, 2014) and precipitation intensity was calculated for 7 average recurrence intervals (1, 2, 5, 10, 20, 50 and 100 years) for each of 4 precipitation durations (5, 10, 20 and 30 min). Runoff (Q) was calculated as the difference between precipitation for each scenario and the saturated hydraulic conductivity of each habitat type (Yang and Zhang, 2011). Runoff (Q CN ) was also estimated through a second method, applying the SCS Runoff Curve Number Model (U.S.D.A, 1986):…”

“…Currently, very few studies have investigated the variability of soil hydrological properties in urban ecosystems through empirical measurements (e.g. Gregory et al, 2006;Yang and Zhang, 2011).…”

Soil hydraulic conductivity as affected by vegetation restoration age on the Loess Plateau, China

“…Infiltration rate was fast in soils with more sand and less clay contents because soils enriched with sand had more large pores and were less likely to be compacted by trample; consequently, they had high hydraulic conductivity (Chartier et al, 2011). In addition, sand has a lower viscosity coefficient and soil water suction than do clay and silt, even when pore sizes are similar, which leads to higher infiltration rates in sandy soils (Yang and Zhang, 2011).…”

“…This process increases bulk density and decreases porosity, which can significantly reduce soil infiltration (Yang and Zhang, 2011). In the early restoration stage, with low vegetation cover, raindrops hit the ground directly and caused natural compaction, which increased bulk density and decreased porosity and hydraulic conductivity ( Table 2).…”

A Simplified Infiltration Model for Predicting Cumulative Infiltration during Vertical Line Source Irrigation

“…Soil bulk density is an important factor that affects soil infiltration capacity. Under the same soil conditions, with soil bulk density increasing, soil porosity decreases, resulting in a decrease in soil infiltration capacity [13][14][15]. In addition, soil initial water content determines the soil water potential during the initial water infiltration stage, thereby significantly affecting the process of soil infiltration [16,17].…”