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Laboratory experiments were carried out to explore the effect of thermal shocks (as occur during fire) and simulated rainfall events on cation leaching dynamics in an organic rich Leptic Umbrisol soil. The soil samples were collected in the field using specially designed lysimeter boxes that allow sampling and application of thermal shock treatments and simulated rainfall while keeping the soil structure unaltered. The soil temperature during the thermal shocks and degree-hours of accumulated heat were determined, and cation (Na[sup +] , K[sup +] , Ca[sup 2+] and Mg[sup 2+] ) leaching was measured in surface runoff (0-cm depth) and subsurface flow (12-cm depth) samples collected from the lysimeter boxes. Important differences were found in cation leaching in relation to thermal shock: monovalent cation leaching from the soil above 200°C (68 degree-hours) and divalent cations leaching above 220°C (195 degree-hours) was higher than that seen in other treatments. In general, the amount of cations leached increased with the severity of the thermal shock; however, under moderate conditions, there was a decrease in cation leaching, mainly of monovalent ions. The exchangeable cation losses by leaching in the intense heat treatments were ~80%. This paper reports the results of laboratory experiments to test the effects on cation leaching after thermal shocks and rainfall simulations on unaltered soil samples. The amount of cations leached increased with the severity of the thermal shock; however, under moderate conditions, there was a decrease in cation leaching, mainly of monovalent ions. [ABSTRACT FROM AUTHOR]

A correction to the article "Enhanced efficiency of pluvial flood risk estimation in urban areas using spatial-temporal rainfall simulations" is presented.

The article discusses the development of a hurricane stimulator by scientists at the University of Florida in Gainesville, Florida, which will help them in studying the damage caused by storms to structures. The device consists of five-foot-tall industrial fans connected to four marine diesel engines and a 5,000-gallon tank of water that cools the engines. The device can create storms equivalent in strength to Category 3 storms and produce rainfall of up to 35 inches per hour. According to Forrest Masters, a researcher who led the project, it will help in assessing how residential buildings are affected by hurricanes and tornadoes.

Revegetation, or other erosion control treatments of disturbed soil slopes in forested areas and along highways of the Lake Tahoe basin are directed at reduction of sediment loading to waterways reaching the lake. However, following treatment, little vegetation monitoring, or hydrologic evaluation has been conducted either to determine if the various treatments are successful or to assess the duration of erosion control anticipated in the field. Here, we build upon results from use of the portable rainfall simulator (RS) described in the first two papers of this series to evaluate cover and revegetation treatment effects on runoff rates and sediment concentrations and yields from disturbed granitic and volcanic soils in the basin. The effects of slope on rainfall runoff, infiltration and erosion rates were determined at several revegetated road cut and ski run sites. Rainfall simulation (∼60 mm h−1, approximating a 100‐year, 15‐minute storm) had a mean drop size of ∼2·1 mm and approximately 70 per cent of ‘natural’ rainfall kinetic energy. Measurements of: time to runoff; infiltration; runoff amount; sediment yield; and average sediment concentration were obtained. Runoff sediment concentrations and yields from sparsely covered volcanic and bare granitic soils can be correlated to slope. Sediment concentrations and yields from nearly bare volcanic soils exceeded those from granitic soils by an order of magnitude across slopes ranging from 30–70 per cent. Revegetation, or application of pine‐needle mulch covers to both soil types dramatically decreased sediment concentrations and yields. Incorporation of woodchips or soil rehabilitation that includes tillage, use of amendments (biosol, compost) and mulch covers together with plant seeding resulted in little or no runoff or sediment yield from both soils. Repeated measurements of sediment concentrations and yields in the subsequent two years following woodchip or soil rehabilitation treatments continued to result in little or no runoff. Revegetation treatments involving only use of grasses to cover the soils were largely ineffective due to sparse sustainable coverage (< 35 per cent) and inadequate infiltration rates. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A rainfall simulation study was performed on twelve vegetative filter strips (VFS), six 1.5 ¥ 4.6 m (5 ¥ 15 ft) long, and six 1.5 ¥ 9.1 m (5 ¥ 30 ft) long, to determine: (1) the effects of vegetative filter strips on atrazine and sediment transport in runoff inflow with an average of 7,650 mg L-1 (0.0638 lb gal-1) sediment (WS) and no-sediment (NS), and (2) the effects of vegetative filter strips length (4.6 and 9.1 m) (15 and 30 ft), and thus area ratio (with constant width), on atrazine and sediment transport. Herbicide runoff losses were simulated by adding a dilute atrazine solution as inflow (with sediment and without sediment) to the upper end of the vegetative filter strips. The with-sediment (WS) treatment was used to represent conventional tillage, while the without-sediment (NS) treatment represented no-tillage. Atrazine, and bromide (Br-) as a hydrologic tracer, were dissolved in the inflow to the vegetative filter strips at a concentration of approximately 1 and 23 mg L-1 (8.345 and 192 lb (mil gal)-1), respectively. The results showed that for the with-sediment inflow treatment, the 87% reduction in sediment transport for the 9.1 m (30 ft) vegetative filter strips was significantly (P = 0.05) greater than the 71% reduction for the 4.6 m (15 ft) vegetative filter strips. There was no significant difference in atrazine transport between the with-sediment and without-sediment treatments, but the 80% reduction in atrazine tra`port for the 9.1m (30 ft) vegetative filter strips was significantly greater than the 31% reduction for the 4.6 m (15 ft) vegetative filter strips. Infiltration of inflow was a dominant factor in reducing atrazine transport with vegetative filter strips, and the Br- data showed that a higher proportion of inflow infiltrated than did rainfall. [ABSTRACT FROM AUTHOR]

Studies have shown that the surface hydrology of a pasture system is influenced by its vegetative characteristics. As research continues on ways to prevent erosion and excessive nutrient loss from agricultural land, the effect that different forage species have on surface runoff requires further investigation. This study sought to evaluate the effect of five forage species at varying canopy heights (one day vs. six weeks growth post-harvest) on surface runoff and infiltration on 6.1 m x 6.1 m (20 x 20 ft) plots fertilized with poultry litter. The five forage species were: Alamo switchgrass (Panicum virgatum Carl Linnaeus), Caucasian bluestem (Bothriochloa caucasia (Trin.) C.E. Hubbard), Greenfield bermudagrass (Cynodon dactylon (L.) Christian Hendrik Persoon), Pete eastern gamagrass (Tripsacum dactyloides (L.) Carl Linnaeus), and Kentucky-31 tall fescue (Festuca arundinacea John H. Schreber). Poultry litter was surface-applied annually at 8.97 Mg ha-1 (4.0 ton/acre). Rainfall simulations (5.0 cm hr-1) (2.0 in hr-1) were used to produce runoff events during spring, summer, and fall to examine seasonal variations. Although there were no statistical differences in runoff volumes between cut canopy and full canopy covers within a single species, runoff volumes were reduced by full canopies, for all seasons, by an average of 18% for all species except bermudagrass. Comparisons of runoff volumes between the different species showed that tall fescue had significantly lesser (30 mm) runoff for three of the four runoff events. There were no differences in runoff between the other four species, for any runoff event. Infiltration was on average 19% greater in tall fescue plots for all runoff events, compared to the other four species. Neutron probe data supported these results, with tall fescue plots consistently having average profile volumetric water content from 3 to 5 m3 m-3 (9.8 to 16.4 ft3 ft-3) lower at the 20 and 35 cm (7.9 and 13.8 in) depths. Results of this study show that tall fescue, when directly compared to the other forages in this study, is more effective at reducing runoff volumes and increasing infiltration, thereby reducing edge of field loss in forage systems. [ABSTRACT FROM AUTHOR]

Lab studies provide an opportunity to isolate processes influencing water, sediment, and agrichemical transport under standard conditions. However, extending this information to field or watershed scales is often difficult. We compared runoff (R) and sediment (E) losses from a lab study with field data from a Tifton loamy sand (3% slope). Three plot scales/length-rainfall simulator methodologies were used: 1.) 0.32 m2 lab pan (L = 0.6 m) under an oscillating nozzle rainfall simulator; 2.) 5.5 m2 field plot (L = 3 m) under a Wobbler nozzle rainulator, and 3.) 600 m2 field plots (L = 43 m) under the same rainulator used in method 2. For field plots (methods 2 and 3), R and E losses were measured from six simulated rainfall events (I = 25.4 mm hr-1, 2 hr duration) during two corn growing seasons (five days before agrichemical application and 1, 14, 29, 49, and 108 days after agrichemical application). Similar rainfall intensity and duration were used in the lab study. R and E losses from lab pan (method 1) and 5.5 m2 field plots (method 2) were measured at 5 minute intervals, whereas R and E delivery for 600 m2 plots (method 3) were measured continuously and at selected times, respectively. R and E rates from all methods generally increased during each event with similar maximum rates. Total R and E for method 2 was at least an order of magnitude greater than those for method 1, and total R and E for method 3 were at least 1 order of magnitude greater than those for method 2. R and E were related to slope length (R2 = 0.94-0.99). Exponents (b) for R and E were 0.50--1.63. Detachment and transport processes varied spatially. Once a critical slope length was exceeded, rilling occurred. Rilling was non existent in method 1 and was present but not dominant in method 2. For method 3, slope length was sufficient to cause rilling, therefore E was greater than that for methods 1 and 2. [ABSTRACT FROM AUTHOR]