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Discontinuous ephemeral streams

Discontinuous ephemeral streams
Alluvial cone ; Base level ; Channel geometry ; Climatic variation ; Fluvial dynamics ; Fluvial erosion ; Land use ; Lithology ; Plant cover ; Semi-arid area ; Southern United States ; Stream ; United States of America
Many ephemeral streams in western North America flowed over smooth valley floors before transformation from shallow discontinuous channels into deep arroyos. These inherently unstable streams of semiarid regions are sensitive to short-term climatic
changes, and to human impacts, because hillslopes supply abundant sediment to infrequent large streamflow events. Discontinuous ephemeral streams appear to be constantly changing as they alternate between 2 primary modes; either aggradation or degradation

Ephemeral gully erosion in southern Navarra (Spain)

Ephemeral gully erosion in southern Navarra (Spain)
Ephemeral gully erosion is a common type of water erosion in the loamy soils formed on the Miocene Marls of southern Navarra. A study has been conducted to describe the different types of ephemeral gullies and to determine their origin, evolution
and importance as sediment sources. 3 main types were identified according to their origin : classic ephemeral gullies formed within the same field where runoff starts, drainage ephemeral gullies collecting the runoff from another upstream area, and discontinuity
ephemeral gullies due to some abrupt slope change in the landscape.

Testing the ephemeral gully erosion model (EGEM) for two Mediterranean environments

Testing the ephemeral gully erosion model (EGEM) for two Mediterranean environments
An EGEM-input data set for 86 ephemeral gullies was collected : detailed measurements of 46 ephemeral gullies were made in intensively cultivated land in southeast Spain (Guadalentin study area) and another 40 ephemeral gullies were measured in both
intensively cultivated land and abandoned land in southeast Portugal (Alentejo study area). Together with the assessment of all EGEM-input parameters, the actual eroded volume for each ephemeral gully was also determined in the field. The resulting
relationship between predicted and measured ephemeral gully cross-sections is rather weak.

Ephemeral gullies. A spatial and temporal analysis of their characteristics, importance and prediction

Ephemeral gullies. A spatial and temporal analysis of their characteristics, importance and prediction
Ephemeral gully erosion is a significant water erosion process, accounting for 50% of the total sediment production in agricultural catchments in the Belgian loess belt. Therefore the aim of this study is to address 4 basic questions : what
are the ephemeral gully characteristics ? why is ephemeral gully erosion an important water erosion process ? when/where will ephemeral gullies occur ? how do ephemeral gullies evolve over time ?

Automated water sampling in ephemeral hydrological systems

Automated water sampling in ephemeral hydrological systems
are ephemeral with detailed information being required on water quality and sediment runoff in conjunction with accurate flow measurements.

Accuracy of methods for field assessment of rill and ephemeral gully erosion

Accuracy of methods for field assessment of rill and ephemeral gully erosion
The aim of this paper is to provide information for a suitable assessment of rill and ephemeral gully erosion with direct measurement methods. Channel size and shape have a great influence on measurement errors.

Data generation processes for spatial series: the example of ephemeral channel form

Data generation processes for spatial series: the example of ephemeral channel form
Recently developed techniques for time series analysis are applied to channel width and slope series collected in small ephemeral channels in Southern Italy. Tests for the difference between trend and difference stationarity, although developed
in the field econometrics, are found to be more suitable for data generation processes in geomorphology. The ephemeral channel data exhibit trend stationarity and the results of spectral analysis and vector autoregression analysis of detrended channel width

Geomorphic threshold conditions for ephemeral gully incision

Geomorphic threshold conditions for ephemeral gully incision
In this paper the available information on the initiation and location of (ephemeral) gullies is summarised, focusing on the relationship between the upslope drainage area and the critical slope gradient for ephemeral gully initiation. Furthermore

Application of the EGEM model to predict ephemeral gully erosion in Sicily, Italy

Application of the EGEM model to predict ephemeral gully erosion in Sicily, Italy
The aim of this paper is to evaluate the performance of the ephemeral gully erosion model (EGEM) adapted to local conditions compared with that of simple empirical equations. A data set of 92 ephemeral gullies formed between 1995 and 2000 in a wheat

The ephemeral historic district in Jakarta

The ephemeral historic district in Jakarta

Structural instability and ephemeral channel behaviour

Structural instability and ephemeral channel behaviour

Assessment of soil losses by ephemeral gully erosion using high-altitude (stereo) aerial photographs

Assessment of soil losses by ephemeral gully erosion using high-altitude (stereo) aerial photographs
The objective of this study is to explore in a critical way the potential of high-altitude (stereo) aerial photographs for the assessment of ephemeral gully erosion rates. On 28 May 1995, an intensive rainfall event occurred in central Belgium
. Ephemeral gullies formed within an area of 218 ha were mapped and measured both in the field and by high-altitude aerial photos taken at the same time. Comparison of these 2 methods shows that if only one of the 2 surveying techniques had been used, only 75
per cent of the total ephemeral gully length would have been detected. So a correction factor is proposed.

Topographical thresholds for ephemeral gully initiation in intensively cultivated areas of the Mediterranean

Topographical thresholds for ephemeral gully initiation in intensively cultivated areas of the Mediterranean
Ephemeral gullying is an important erosion process in Mediterranean areas. The objective of this study was to investigate to what extent one could use field measurements of S (local slope) and A (drainage-basin area) to predict the location
of ephemeral gully initiation in intensively cultivated Mediterranean environments. Two relatively homogeneous study areas in Southeast Spain and Northeast Portugal with widespread ephemeral gullying were selected.

Changes in vegetation composition and diversity in relation to morphometry, soil and grazing on a hyper-arid watershed in the central Saudi Arabia

Arid area ; Biodiversity ; Ephemeral stream ; Geomorphometry ; Over-grazing ; Saudi Arabia ; Soil properties ; Vegetation ; Watershed
[b1] Dept. of Plant Production, College of Food and Agriculture Sciences, King Saud Univ., Riyadh, Arabie Saoudite

The activation of ephemeral streams in karst catchments of semi-arid regions

The activation of ephemeral streams in karst catchments of semi-arid regions
Drainage network ; Ephemeral stream ; Flood ; Italy ; Karst ; Modelling ; Precipitation ; Puglia ; Runoff ; Semi-arid area ; Watershed
This work presents an analysis of the response to rainfall of ephemeral streams in a karst semi-arid regions of southeast of Italy by an innovative approach. The analysis is based on a 2D simulation model of the behavior of a network of ephemeral
response of ephemeral streams to the rainfall, whereas more extreme rainfall events generate quick and high discharge responses of the ephemeral streams. In addition, modeling results emphasize the non-linearity of runoff generation, in particular for some

Flood events in Mediterranean ephemeral streams (ramblas) in Valencia region, Spain

Flood events in Mediterranean ephemeral streams (ramblas) in Valencia region, Spain
This paper analyses the hydrological processes of flood events in three Mediterranean ephemeral streams, taking into account the peculiarities of the rainfall and morphology patterns of the study area. Daily and other detailed information (every 5

Formation and evacuation of a large gravel-bar deposited during a major flood in a Mediterranean ephemeral stream, Nahal Me'arot, NW Israel

Formation and evacuation of a large gravel-bar deposited during a major flood in a Mediterranean ephemeral stream, Nahal Me'arot, NW Israel
This study describes the morphological impact and the hydrological characteristics of a large flood event in a small coastal Mediterranean ephemeral stream in Mt. Carmel using the aftermath channel and floodplain morphology. The hydrological

Runoff and sediment discharge in a semiarid ephemeral drainage basin

Runoff and sediment discharge in a semiarid ephemeral drainage basin
Most of the sediment load of the Red Deer River, Alberta, Canada, is derived from a badland area which forms less than 2 per cent of the drainage basin. This paper describes results from a small instrumented ephemeral basin set up to determine

Urbanization and adjustment of ephemeral stream channels

Urbanization and adjustment of ephemeral stream channels
This paper examines the case of Fountain Hills, a residential area near Phoenix, Arizona, as an example of urban impacts on a representative ephemeral channel in a dryland environment. Three specific questions are addressed : how has urbanization

Modeling scour and deposition in ephemeral channels after wildfire

Modeling scour and deposition in ephemeral channels after wildfire
of modeling sediment transport in ephemeral channels following wildfire.

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