Amc ii, the second with an average of amc ii and amc iii, and the third with amc iii. The runoff curve number also called a curve number or simply cn is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. Urban hydrology, as commonly practiced, is an inexact science at best. Per the existing hydrology map the southerly flowing cucamonga channel divides the site into parce l areas of 207 acres westerly watersheds 1. Procedures for identifying parameters southwest watershed. The science and study concerned with the occurrence, circulaton, i distribution and properties of the waters of the earth and its atmosphere, including precipitation, runoff and. Working curve for manual computation from type ii storm distribution, table 1. The science and study concerned with the occurrence, circulaton, i distribution and properties of the waters of the earth and its atmosphere, including precipitation, runoff and groundwater.
Runoff curve numbers for hydrological soilcover complexes for antecedent rainfall condition ii and i a 0. Amci for dry, amcii for normal, and amciii for wet conditions. In flood hydrology baseflow is generally dealt with separately, and all other types are combined into direct runoff, which consists of channel runoff, surface runoff, and subsurface flow in unknown proportions. Chapter 10 estimation of direct runoff from storm rainfall. It should be noted that the cn values were first calculated.
The purpose of this study was to provide a preliminary drainage study to comply with submittal requirements of san bernardino county for cup purposes. More parameters to describe the land conditions at a site. Graph showing a comparison of the cns estimated using the usgs measured flows and the cns estimated using the cn amc regression for drainage areas less than 2,000 acres. Representation of the handbook amc i, amc ii, amc iii relationships. Hydrology the san bernardino county hydrology manual reference 1, was used to develop the hydrological parameters for the hydrology analyses. Part 654 national engineering handbook chapter 5 stream hydrology 5ii 210vineh, august 2007 tables table 51 sensitivity analysis on gage record, willow creek case 58 study table 52 kvalues for the gumbel extreme value distribution 512 table 53 kvalues for the logpearson type iii distribution 5 table 54 discharge peaks, with basic statistics 515. Further more the module is a elective part of the master. Applying neh4 1964 for the nonfreezing conditions in riverside county the amc conditions are. The asceewri curve number hydrology task committee sponsored by environmental and water resources institute ewri. Amc i for dry, amc ii for normal, and amc iii for wet conditions. Hydrology 33 this chapter is about water the supplies of water that exist in and around the parkway vision plan area, the ways that water moves between the earths atmosphere, surface, and subsurface, the demands that people have placed on this resource, and fi nally, the impacts that those demands. Antecedent moisture condition amc condition is defined on the total rainfall of previous five days before the event.
Askar salahaddin university, kurdistan region, iraq abstracts this research aims to determine the runoff depth using soil conservation the service curve number scscn method with geographic information technique gis. Most professional hydrologists would hold their noses at some of the methods commonly used. Amc ii 12,7 27,9 35,653,3 amc iii 27,9 53,3 for different land uses hydrolithical categories the cn values are presented in table iii. Tr55 curve number tables appendix 4b page 4b4 wsdot highway runoff manual m 3116. Rainfallrunoff estimation using scscn and gis approach in the. The value for initial abstraction was left blank in the hms input file. Provide drainage easements where drainage courses can affect existing and proposed facilities and cause dra\. Course introduction, water balance equation pdf aquifers, porosity, and darcys law pdf hydraulic head and fluid potential pdf. Table ii amc values condition of soil winter period october april rest periods mayseptember amc i 27,9 53,3 for different land uses hydrolithical categories the cn values are presented in table iii. Existing hydrology the site shows signs that it has been tilled at some date in its past, but is currently weedladen openspace flatland with gradients of 0.
Rainfallrunoff model using the scscn method and geographic information systems. The amc iii and amc i gave results of dramatic difference. It should be noted that the cn values were first calculated using amc ii conditions, as represented in table 4. Due to this, it is almost impossible to give any exact answers.
It also causes other problems that affect soil and water. Application of curve number method for estimation of. Amc of ii as it is representative of typical conditions, rather than the extremes of dry conditions amc i or saturated conditions amc iii. Some will enter as interflow just below the surface of the land a very porous horizon shallow flow system. The asceewri curve number hydrology task committee.
Scs runoff cn for hydrologic soil cover complex under amc ii condition for the. The course hydrology iii is a part of the module hydropedology, which is ingredient of geoecology master degree course. Some of the figures in these lecture notes are adapted from or inspired by illustrations in dingman, s. Antecedent moisture content amc equal to 2 for the 10year frequency storm was used in the calculations. Moreover, under amc based estimations, the modified cn i method also performed best r 2 0. The storativity is then defined in terms of the api such that. For tentative tract maps, the goal of the hydrology study is to provide flood protection through identification and protection of drainage courses. Journal of environmental hydrology 2 volume 6 paper 7 july 1998. The rational method and unit hydrograph method were used for the analyses and the computations were performed using the computer program developed by civil caddcivil design. Hydrology manual iii january 2006 chapter 7 runoff calculation methods 58 7. Arid region hydrology addendum faqs our study includes a large watersheds that cover s 2 different amc areas. Graph showing a comparison of the cns estimated using the usgs measured flows and the cns estimated using the cn amc. The curve number method was developed by the usda natural resources conservation service, which was formerly called the soil conservation service or scs the number is still popularly known as a scs runoff curve.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Results of the hydrologic calculations are shown in table 1 below. The curve numbers for amc ii average condition for each landcoversoil compound can be found in handbook of hydrology 1972, for indian conditions. Watershedscale amc selection for hydrologic modeling. Chapter 5 stream hydrology 5ii 210vineh, august 2007 tables table 51 sensitivity analysis on gage record, willow creek case 58 study table 52 kvalues for the gumbel extreme value distribution 512 table 53 kvalues for the logpearson type iii distribution 5 table 54 discharge peaks, with basic statistics 515.
The other moisture conditions are dry, amc i or, and moist, amc iii or. Dec 01, 20 more parameters to describe the land conditions at a site. Table gives seasonal rainfall limits for these three antecedent moisture conditions. A method for estimatingvolume and rate of runoff in small. The curve number method estimates this combined direct runoff. Hydrology studio uses the unit hydrograph method for calculating nrcs runoff hydrographs. Module hydropedology is one of three obligatory modules within the area of specification called river basin management. Pdf this paper presents a rain durationdependent procedure based on the popular soil conservation service. As part of programs established to alleviate these problems, engi. Use the appropriate amc designation for each subarea. Per the existing hydrology map the southerly flowing cucamonga channel divides the site into parce l.
Application of curve number method for estimation of runoff. The study of hydrology helps us to know i the maximum probable flood that may occur at a given site and its frequency. The study is based on the hydrology manual of san bernardino county and the april 2010 addendum to the hydrology manual. Luis parra, the amc condition is based on the rainfall record. Apr 12, 2010 arid region hydrology addendum faqs our study includes a large watersheds that cover s 2 different amc areas. Some will flow over land surface as runoff relatively commonimportant when the ground is frozen. Urban hydrology is a compromise between accuracy and data availability. Part 630 hydrology national engineering handbook chapter 10 estimation of direct runoff from storm rainfall rain clouds cloud formation precipitation t r a n s p i r a t i o n f r o m s o i l f r o m o c e a n t r a n s p i r a t i o n ocean ground water rock deep percolation soil. This method is basically the same approach as used in the original tr20. Amc ii to amc i or amc iii curve number amc ii amc i dry amc iii wet 10 0. Determine the soil types and convert them into hydrological soil groups like.
Urban hydrology for small watersheds chapter 1 introductionintroduction the conversion of rural land to urban land usually increases erosion and the discharge and volume of storm runoff in a watershed. Journal of environmental hydrology 1 volume 11 paper october 2003 journal of environmental hydrology issn 10583912. Amc equal to 3 was used for the 100year frequency storm. Using runoff curve numbers cn from lulc and soil type taken for the dry conditions amc i, average conditions amc ii and wet conditions amc iii, we can. National institute of hydrology, roorkee, ua 247 667, india. For modeling purposes, amc ii in watershed is essentially an. A design storm is selected typically an nrcs 24hr distribution.
Cn according to amc based on the total rainfall in the 5day period preceding a storm. Factors for converting amc ii to amc i or amr iii cn amc ii conversion factor amc i amc iii 10 0. For post development analysis, amc iii should be used for soil loss rates. Runoff conditions for converting storm rainfall to runoff with scs. Map showing the cn amc regions analyzed in sd for this study.
Journal of environmental hydrology 4 volume 6 paper 7 july 1998 curve number applicability to large watersheds johnson use and soil drainage characteristics under amc ii conditions and fixed as a constant. Amc i, amc ii and amc iii, these are based on different soil conditions shown in table 1. The reason is that the methods are a number of steps back from our best statistical estimate of reality. Graph showing comparisons of the cns for amc i, ii, and iii. A unit hydrograph is constructed based on the drainage areas characteristics, i. Runoff estimation in watershed gp10 using nrcs cn and gis. Rainfallrunoff model using the scscn method and geographic. Are there any proposed changes for those areas that are designated as amc iii. In some cases, sub area delineation should be based on amc boundaries. Eciv 562 engineering hydrology department of civil and environmental engineering, university of south carolina nrcs scs curve number runoff model a popular, widely accepted and applied method, particularly in south carolina, to determine rainfall excess direct storm runoff is the nrcs curve number runoff model. Pdf a rain duration and modified amcdependent scscn. Curve number hydrology development, status, and updates claudia c. This illustration incorporates a graph not to scale displaying the average stream gradients along the ventura river from rm river mile 0.
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