An official website of the United States government
Landslides along Alabama highways are a relatively common occurrence in many regions of the state. These landslides can lead to damage to transportation infrastructure and significant traffic disruptions. The current practice identifies landslide locations primarily through maintenance personnel reports or motorist complaints. Once an unstable region is identified, the suspected slide area is commonly instrumented with inclinometers, which are then read at regular intervals to understand the slide plane location and identify changes in behavior. This inclinometer data has been collected at unstable sites across the state for many years and provides a unique dataset to understand how precipitation events influence landslide behavior along highways. Previously developed precipitation thresholds considering storm magnitude and duration were consistent with landslide events observed around the state, but there are many non-triggering events that fall above the thresholds (false positives). Approximately 70% of false positive storm events occurred during drier than average periods based on normalized soil moisture data from NASA’s SMAP instrument, while large movements occurred primarily during periods of average or above average soil moisture. This suggests that adding soil moisture data to landslide threshold predictions may help to reduce false positive events and to assess the likelihood of large movements occurring. These findings are now being used to develop improved warning thresholds that can highlight when landslides are likely to occur, allowing inspections and preventative maintenance to be prioritized.
more »
« less
This content will become publicly available on March 1, 2026
Identifying preferential flow from soil moisture time series: Review of methodologies
Abstract Identifying and quantifying preferential flow (PF) through soil—the rapid movement of water through spatially distinct pathways in the subsurface—is vital to understanding how the hydrologic cycle responds to climate, land cover, and anthropogenic changes. In recent decades, methods have been developed that use measured soil moisture time series to identify PF. Because they allow for continuous monitoring and are relatively easy to implement, these methods have become an important tool for recognizing when, where, and under what conditions PF occurs. The methods seek to identify a pattern or quantification that indicates the occurrence of PF. Most commonly, the chosen signature is either (1) a nonsequential response to infiltrated water, in which soil moisture responses do not occur in order of shallowest to deepest, or (2) a velocity criterion, in which newly infiltrated water is detected at depth earlier than is possible by nonpreferential flow processes. Alternative signatures have also been developed that have certain advantages but are less commonly utilized. Choosing among these possible signatures requires attention to their pertinent characteristics, including susceptibility to errors, possible bias toward false negatives or false positives, reliance on subjective judgments, and possible requirements for additional types of data. We review 77 studies that have applied such methods to highlight important information for readers who want to identify PF from soil moisture data and to inform those who aim to develop new methods or improve existing ones.
more »
« less
- PAR ID:
- 10587408
- Publisher / Repository:
- American Society of Agronomy
- Date Published:
- Journal Name:
- Vadose Zone Journal
- Volume:
- 24
- Issue:
- 2
- ISSN:
- 1539-1663
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The hydro-mechanical behavior of unsaturated soil, particularly expansive soil, is influenced significantly by cyclic wetting and drying. Understanding the soil parameters is crucial when evaluating the performance of infrastructures constructed on expansive clay. As a result of extreme rainfall events, highway slopes containing highly expansive Yazoo clay in Mississippi, U.S., become vulnerable to volume change. The phenomenon creates perched water zones within the slopes and poses a risk of slope failure. The soil-water characteristic curve (SWCC) defines the relationship between water content and soil suction, which can be obtained from different laboratory procedures. However, conventional laboratory methods have some limitations. To address this, various analytical and predictive models have been developed, but they can only offer estimates based on soil characteristics and lack seasonal variations occurring in field conditions. Studying seasonal SWCC through field measurements can help understand soil responses to changing moisture conditions. The current study utilized field data from six highway slopes in Mississippi and classified the data into different seasons: spring, summer, and fall. After obtaining van Genuchten parameters from the fitted curve for each season, the finite element method was applied to evaluate the parameters for accurate numerical analysis of infrastructures containing expansive clay. The study observed the variations in flow parameters with seasonal change that cannot be achieved when data from only one season is considered. The findings underscore the importance of field instrumentation data for developing SWCC and the significance of seasonal flow parameters in infrastructure design.more » « less
-
Abstract Levees play a critical role in safeguarding communities and assets from flooding, acting as essential defenses against the devastating impacts of inundation. Yet, earthen levees are prone to breaches, especially in the face of swift floodwaters. Distributed low-cost sensor networks offer the potential to generate spatial maps illustrating soil moisture levels. Long-term monitoring of these spatial maps could identify vulnerable zones in the levee while providing an understanding of how climate change affects levee stability. This study presents an investigation into spatial monitoring of soil saturation in levees using a wireless network of UAV-deployable sensing spike packages. The goal of this paper is to demonstrate the use of these sensors for assessing soil conductivity levels in sand-filled embankments. The obtained soil conductivity levels are crucial for determining soil saturation. The developed sensing spikes consist of a spike that penetrates the ground and measures conductivity between two electrically conductive contacts. The sensing spike consists of microprocessors for edge computing, and wireless data communication systems that report data to a way station in real-time. To validate the efficacy of the developed sensors, a flume test is developed as a replica of a levee and monitored under controlled water flow conditions. The analysis of data at different times revealed the progression of moisture throughout the earthen embankment. Initially, the soil is almost dry. As the controlled water flow proceeds, the soil becomes partially saturated, with the final stage showing a dominant presence of saturated soil. The collected data sampled at the measurement points is expanded to a continuous moisture profile using kriging. Gaussian kriging, also known as ordinary kriging, is one of the commonly used variants of the kriging method. In Gaussian kriging, the estimation of values at unsampled locations is based on a linear combination of nearby data points, with weights determined by their spatial relationships. The Gaussian assumption implies that the errors in the estimation process follow a normal distribution. The extended knowledge about saturation levels obtained through kriging can lead to insights for predicting vulnerable areas and preempting potential failures. Overall, this study paves the way for further development of a wireless network of sensing spike packages as a UAV-deployable system for levee health assessment and improved infrastructure management.more » « less
-
Almost every aspect of the global water cycle involves a mixture of fluids and particles – raindrop formation, ocean currents and water percolation through the soil. This mixture of gas and liquid or liquid and solid causes behaviour that is important to understand, but difficult to predict. This is particularly true when turbulent flow occurs. Dr Lian-Ping Wang at the University of Delaware has developed models and methods that have greatly improved our ability to understand and predict phenomena from localised rainfall patterns to particle transport in industrial processes.more » « less
-
Climate models project changing patterns of precipitation and increases in temperature that modify soil moisture dynamics. Land use and changing frequency and intensity of precipitation can induce changes in soil structure and rooting abundances at timescales shorter than commonly considered. Soil structure is a critical ecosystem that governs water flow through soil profiles and across landscapes, and can influence weathering rates and thus solute release and soil development. We hypothesize that the altered soil structure and modification of rooting depth distributions linked to land use change can influence soil solute concentrations, and that those shifts in solute release are dependent on patterns of precipitation. We installed suction lysimeters to collect soil water for ~3 y in two grassland regions with distinct mean annual precipitation (800 mm y-1, 1100 mm y-1) in native prairie, agriculture, and post-agriculture land uses at depths of 10, 40, and 120 cm. We linked solute concentrations to soil moisture, aggregate-size distribution, pore geometry, and rooting depth distributions to assess how land use change and the altered rooting abundance it imposes can modify soil structure and hydrologic fluxes, and to infer how soil weathering can shift deep in the subsurface. We reveal how soil moisture residence time and the soil pore network can govern solute production, and the importance of precipitation and thus of soil moisture accumulation over growing seasons for mineral weathering and solute production. Specifically, we find that the solubility potential of multiple weathering products and organic carbon increases with precipitation, dominance of relatively small aggregates at the surface, and fewer coarse roots. Enhanced solute concentrations at depth may also reflect transport down-profile. Our findings reveal unintended consequences of land use change that influence important hydrologic dynamics and nutrient cycling in the vadose zone and how deeply and how persistently unexpected consequences of changes in land cover can propagate.more » « less
