As a result, the peak discharge, volume, and frequency of floods increase in nearby streams. Changes to stream channels during urban development can limit their capacity to convey floodwaters. Roads and buildings constructed in flood-prone areas are exposed to increased flood hazards, including inundation and erosion, as new development continues.
presented in Figure 1, increased runoff causes the volume of water to increase rapidly, pushing the peak discharge of the stream much higher for the same storm event. The higher the discharge the more power the stream has for erosion, Table 1: Percent Impervious Cover Typically Associated With Urban Areas Land Use Percent Impervious Cover
construction, and maintenance strategies for the property to maintain or restore, to ... mitigate the impacts of increased peak runoff rates. However, wet ponds and similar practices ... The predevelopment peak discharge rate is also much lower than the post-development peak discharge rate due to attenuation and absorption by soils and ...
Duration of rainfall - For a given amount of total storm rainfall, the shorter the time period it occurs in, the greater the peak discharge should be. If the same amount of rainfall occurs in a longer period, the peak discharge should decrease. NRCS adopted a …
Dimensionless analyses were used to determine the equation form of linear regression analyses. The results revealed that the peak flow rate was significantly correlated with plot area, slope steepness, runoff depth, rainfall depth and the maximum 30-min rainfall intensity.Mar 9, 2017
The average golf course uses 312 gallons of water per day for maintenance of the grounds. As this water flows through the property, it can pick up contaminants such as petroleum, pesticides, and fertilizers.Jan 30, 2019
It can be pretty darn dark out on the golf course when there is no moonlight. Adequate lighting and training need to be considered to operate in a safe manner. Most golf courses do have their irrigation systems running at night, so coordination and timing of irrigation needs to be compatible with any work scheduled.Aug 8, 2011
Chlorpyrifos is an organophosphate insecticide used extensively in the agricultural industry, as well as on golf courses, green houses, and as mosquito adulticide.May 14, 2018
Using technology to pinpoint water usage and minimize water wasting effectively. Utilizing filtered stormwater runoff through wetlands and turf grass. Creating and implementing turf reduction programs. Planting drought-resistant vegetation that can survive on a low water supply.Jan 24, 2019
The case studies were selected to demonstrate the feasibility of providing adequate stormwater control for a range of site conditions and building designs. To the maximum extent technically feasible, each case study includes a description of a method that can be used to determine the design objectives of the project based on retaining the 95th percentile storm. Examples of onsite technologies and practices have also been provided. The case studies are intended to provide examples of modeling procedures that can be used to quantify treatment system performance and processes for assessing sites and determining appropriate control techniques to the maximum extent technically feasible.
Section 438 of that legislation establishes strict stormwater runoff requirements for federal development and redevelopment projects. The provision reads as follows:
In the natural, undisturbed environment rain that falls is quickly absorbed by trees, other vegetation, and the ground. Most rainfall that is not intercepted by leaves infiltrates into the ground or is returned to the atmosphere by the process of evapotranspiration. Very little rainfall becomes stormwater runoff in permeable soil, and runoff generally only occurs with larger precipitation events. Traditional development practices cover large areas of the ground with impervious surfaces such as roads, driveways, sidewalks, and buildings. Under developed conditions runoff occurs even during small precipitation events that would normally be absorbed by the soil and vegetation. The collective force of the increased runoff scours streambeds, erodes stream banks, and causes large quantities of sediment and other entrained pollutants to enter the water body each time it rains (Shaver, et al., 2007; Booth testimony, 2008).
Although Congress did not prescribe specific practices to be used to implement Section 438 it can be inferred that one of the goals of the Act was to promote the use of innovative stormwater management approaches, designs and practices that better protect receiving water quality, flow regimes and provide other important environmental benefits. GI/LID are preferred practices, to be supplemented with or replaced with conventional controls when site specific conditions dictate.
For the purposes of the case study scenarios, the following four categories of practices were selected as the most appropriate practices for implementing Section 438 requirements: bioretention, permeable pavements and pavers, cisterns, and green roofs. These practices were selected based on known performance data and cost. For each case study, the same hierarchy of selection criteria was used, i.e., the most cost effective practices were considered before other practices were considered. Bioretention practices were considered first because these systems generally have the lowest cost per unit of stormwater treated (Hathaway and Hunt, 2007). Thus, if the bioretention system could not be designed to adequately capture the desired runoff volume, permeable pavement and pavers, cisterns, and green roofs were considered in that order based on relative cost. In most cases a combination of practices was selected as part of an integrated treatment system. It should be noted that all treatment systems were designed to accomplish the goal of capturing the 95th percentile rainfall event onsite. Examples of onsite stormwater management practices selected for each site are presented in the results section. For the Boston, MA site, it was assumed that bioretention was not feasible in order to simulate a situation where space was severely limited; as a result, interlocking modular pavers were selected as the most cost-effective stormwater management to capture the requisite design volume. To further illustrate the range of site conditions designers may encounter, and how site conditions impact the selection of appropriate control options, Scenario #3 (Cincinnati, OH) was re-analyzed as Scenario #8. In Scenario #8, it was assumed that the site had clay soils and low infiltrative capacity. Given these site conditions, the range of potential control options was more limited and a combination of modular paving blocks, a green roof, and cisterns was ultimately selected based on cost and site suitability factors.
Eight locations were selected for the 9 case studies as shown in Figure 11 and Table 2. Case study numbers 3 and 8 were both developed based on the Cincinnati, Ohio facility, although the site parameters were altered to represent differing site conditions and design constraints. Annual average rainfall depths for these locations range from 7.5 inches to 48.9 inches. Analyses of the 95th percentile rainfall events for these locations produced rainfall depths that range from 1.00 inch to 1.77 inches (Table 2).
95th percentile rainfall event. The 95th percentile rainfall event represents a precipitation amount which 95 percent of all rainfall events for the period of record do not exceed. In more technical terms, the 95th percentile rainfall event is defined as the measured precipitation depth accumulated over a 24-hour period for the period of record that ranks as the 95th percentile rainfall depth based on the range of all daily event occurrences during this period.
ESD can occur in a variety of forms. One of the most common is through human contact with sensitive devices. Human touch is only sensitive on ESD levels that exceed 4,000V. A recent investigation found the human body and its clothing capable of storing between 500V and 2,500V electrostatic during the normal workday.
As the current dissipates through an object, it's seeking a low impedance path to ground to equalize potentials. In most cases, ESD currents will travel to ground via the metal chassis frame of a device. However, it's well known that current will travel on every available path.
Electrostatic discharge ( ESD) has been around since the beginning of time. However, this natural phenomenon has only become an issue with the widespread use of solid-state electronics. All materials (insulators and conductors alike) are sources of ESD. They are lumped together in what is known as the triboelectric series, ...
Negative charges are more common to synthetic materials such as Styrofoam or plastic cups. The amount of electrostatic charge that can accumulate on any item is dependent on its capacity to store a charge. For example, the human body can store a charge equal to 250 picofarads.
The word static simply means the charge cannot be equalized or transferred through electromotive force until there is a decrease in the capacitance between two objects. An example of this can be your hand (which may hold a negative charge) as it approaches a doorknob (which may hold a positive charge).
120/240 is single phase, not 2 phase. Just because there are 2 hot conductors does not mean it is called 2 phase. It is fed by one transformer with one phase conductor and one neutral, and the secondary side is center tapped to create a grounded conductor which is the neutral.
Peak discharges caused by a high degree of impervious areas upstream, for instance, need to be taken into consideration before site-scale habitat restoration is being implemented, and they must, therefore, be mitigated or managed.
As predicted by Wolman and Gerson (1978), interannual variation in peak discharge is much larger in small, semi-arid watersheds than in large humid watersheds. The ratio of the 100-year flood to the 2-year flood varied from about 2 in large watersheds with peak flows dominated by high-elevation snowmelt to more than 100 in a small ephemeral watershed dominated by runoff from local summer thunderstorms (Table 1 ). In small semi-arid watersheds in the Great Plains, the area–age distribution of flood-plain cottonwood forests varied widely over time and space even between sites along the same creek because of the persistent effects of extreme, local thunderstorms on long-term channel change and tree establishment. By contrast, cottonwood forests along the upper Yellowstone, upper Green, and South Fork Snake rivers, where floods are dominated by high-elevation snowmelt with little interannual variation in peak discharge, had consistent area–age distributions closer to the pattern of exponential decay predicted by a steady-state model of channel change. Watersheds with peak instantaneous annual discharges consisting of a mix of snowmelt and thunderstorm events had forest patterns intermediate between those dominated by snowmelt and those dominated by thunderstorms.
Although the Atrato discharges into the Caribbean Sea ( Figures 1 and 3), its drainage basin is located west of the Cordilleras and has the same drainage basin characteristics as the San Juan and Patía rivers (e.g., headwaters at high elevations, high rainfall rates, and high tectonic activity).
Stationarity studies mainly involve analyzing stationarity of peak discharges; it is, in fact, the flood peak that generally qualifies the severity of the event. The sample used is usually composed of the annual maximum discharges or maxima of episodes exceeding a flow threshold, instantaneous or daily.
River discharge. The volume of water flowing through a river per second. Measured in cubic metres per second (m 3 /s), sometimes abbreviated to cumecs. River discharge can be affected by: the level of precipitation - as precipitation increases, discharge levels also increase. temperature - as temperature increases, ...
When the ground is waterlogged the soil cannot absorb any more moisture, this leads to a reduction in infiltration and an increase in surface runoff. Because surface runoff is faster than throughflow and baseflow, rainfall will reach rivers quicker and reduce lag time. Rock Type - affects lag time and peak discharge.
Man-made impermeable materials such as concrete cover a large proportion of the soil in urban areas. Due to this water is unable to infiltrate the soil, surface runoff is increased and water reaches the rivers faster. This leads to a shorter lag time and an increase in peak discharge.
Hydrographs are graphs that show river discharge over time. Hydrographs show how the volume of water flowing at specific point in a river varies over time. Storm Hydrographs show river discharge around the time of a storm event. Storm Hydrographs only cover a short period of time around a particular storm event ...
Basin lag time (lag time) - the delay between peak rainfall (indicated by the blue Bar Chart in the bottom left hand side of the Hydrograph) and peak flow (peak discharge) (the delay is the time it takes rainwater to flow into the river). A shorter lag time can increase peak flow (discharge), because a greater volume of water reaches ...
Drainage Basin Characteristics - the physical features of a drainage basin, can affect both lag time and peak discharge. Larger drainage basins - size affects the amount of precipitation a drainage basin can catch and hold. Large drainage basins have a higher peak discharge, and generally longer lag times than smaller drainage basins.