Search results for "Runoff curve number"
showing 10 items of 14 documents
Curve Numbers Seasonal Variation in Mid-Mediterranean Area
2018
AbstractThe curve number (CN) method is a popular technique for estimating a rainstorm event’s direct runoff (Q from its storm depth P). It relies on the parameter CN, a lumped expression of a wate...
Chapter 3 patterns and thresholds of runoff generation and sediment transport on some Mediterranean hillslopes
2005
Abstract Runoff and sediment transport data obtained from hillslopes in two limestone areas in southeast Spain are analysed in order to define spatial and temporal thresholds for sediment movement at the patch scale under Mediterranean semiarid and subhumid climatological conditions. The data discussed in this paper include a 7-year series of runoff and sediment collection in open Gerlach plots. The 136 events are analysed in relation to characteristics of rainfall, soil and soil surface components. In both cases slopes behave as a patchwork of runoff and runon areas and the size of the runoff or runon patches being dependent on the climatological conditions. These control the hydrological …
SCS Curve Number and Green-Ampt Infiltration Models
2019
Soil Conservation Service curve number (SCS-CN) and Green-Ampt (GA) infiltration models are probably the most applied equations in practical hydrology to compute the amount of direct runoff from rainfall. Both models are very simple, require few parameters, and present drawbacks and advantages. The empirical CN model concentrates the infiltration effect in the curve number and in the so-called soil hydrological groups, which have been widely characterized for different soil types, land cover, and antecedent soil moisture conditions (ASMCs), although the latter was considered ambiguous, whereas soil hydrological characteristics, including ASMC, are taken into account for the simplified physi…
Annual runoff assessment in arid and semiarid Mediterranean watersheds under the Budyko's framework
2017
The solution of many practical water problems is strictly connected to the availability of reliable and widespread information about runoff. The estimation of mean annual runoff and its interannual variability for any basin over a wide region, even if ungauged, would be fundamental for both water resources assessment and planning and for water quality analysis. Starting from these premises, the main aim of this work is to show a new approach, based on the Budyko's framework, for mapping the mean annual surface runoff and deriving the probability distribution of the annual runoff in arid and semiarid watersheds. As a case study, the entire island of Sicily, Italy, is here proposed. First, ti…
Curve Number: Empirical Evaluation and Comparison with Curve Number Handbook Tables in Sicily
2014
The curve number (CN) method is widely used for estimating direct runoff depth from rainstorms. The procedure is on the basis of the parameter CN, a lumped expression of basin absorption and runoff potential, and a second parameter, initial abstraction (IA), which represents the interception, infiltration, and surface depression during the early part of a storm. The evaluation of CN in Sicily at a basin scale from rainfall-runoff multiday events is done using rainfall-runoff observations during the period 1940–1997 (mean record length of 20 years) in 61 Sicilian watersheds using three different methods: (1) the national engineering handbook, section 4 hydrology (NEH4) method (NEH4M) (the me…
Runoff generation, sediment movement and soil water behaviour on calcareous (limestone) slopes of some Mediterranean environments in southeast Spain
2003
Abstract An interpretation of soil hydrology and erosion data obtained from limestone areas in southeast Spain is presented in the framework of recent hypotheses on runoff generation mechanisms in Mediterranean environments. The main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of Mediterranean limestone slopes. For this purpose, data were collected in a typical limestone area, with climatic characteristics ranging from subhumid to semiarid. Several sites were chosen with comparable slopes, vegetation and soils along a transect of 20 km to carry out several research projects. The data discussed in this paper cons…
Soil erosion and hydrology of the western Mediterranean badlands throughout rainfall simulation experiments: A review
2013
Abstract Rainfall simulation experiments are widely used in geomorphological research in badland areas. This technique contributed significantly to our understanding of badland geomorphology in the Mediterranean belt. Due to the different types of simulated rainfall applied and the variable size of the plots a review of the State-of-the-Art is necessary. This study confirmed that rainfall simulations are well suited to (i) analyse runoff-infiltration processes and sediment detachment within badlands, and (ii) to establish the factors determining the hydrological and erosion response at interrill scale in badland areas. The hydrological response of badlands is characterized by rapid response…
Empirical determination of the average annual runoff coefficient in the Mediterranean area
2014
Runoff estimation in ungauged basin is a challenge for the hydrological engineers and planners. For an y hydrological study on an ungauged basin, a methodology has to be appropriately selected for the determination of runoff at its outlet. Several meth ods have been used to estimate the basin runoff production. In this study the empirical Kennessey m ethod to determine average annual runoff coefficien t, RC, is tested on 61 Sicilian basins characterized b y different climate conditions, surface permeabilit y, mean slope and vegetation cover. A comparison between observed and calculated RC showed that a calibration of the Kennessey model could be necessary. The slight and not satisfying impr…
Exploiting the topographic information in a PDM-based conceptual hydrological model
2014
In this work, a conceptual lumped model was developed to simulate runoff and analyze hydrological processes with the goal of incorporating the morphological information into a probability-distributed model (PDM). PDMs usually describe the process of runoff generation as the result of soil saturation excess caused by precipitation with soil storage capacity represented by a spatially distributed quantity and described by a probability distribution. The proposed model, called topography-based probability distributed model (TOPDM), based on a simple water balance whose components are basin soil moisture storage, precipitation, drainage to groundwater, evapotranspiration, and Dunnian and Horton…
Empirical Investigation of Curve Number Method Parameters in the Mediterranean Area
2012
AbstractThe curve number (CN) method is widely used as a technique for estimating surface runoff depth from rainstorms. This simply lumped method is based on the main parameter CN, which represents the lumped expression of basin absorption, and on a parameter that represents interception, infiltration during the early part of a storm, and surface depression storage, called initial abstraction. In this paper, CN is evaluated at the basin scale from rainfall-runoff multiday events, in the observation period 1940–1997 (recorded length mean equal to 20 years) for 61 Sicilian basins with three different methods: NEH4 method, asymptotic fitting method, and a least-squares method. A first analysis…