New data on the age of the Middle Palaeolithic site of Proniatyn (Podolian Upland)

The Middle Palaeolithic site Proniatyn is geomorphologically located on the near-watershed slope of the right bank of the Seret River. The history of its archaeological research began in 1977. During numerous expedition seasons of works conducted with using of methods of natural sciences and archaeology (until 2015), rich flint material was found on the site, which was located in the deposits of the over-Horokhiv deluvial solifluction stratum, i.e. not in situ, but was moved down the slope. The upper chronological limit of the cultural horizon was determined as 85±7 ka (according to V. Shovkoplias) by TL-dating of the Upper Pleistocene loess, which overlaps the over-Horokhiv deluvial solifluction stratum. In 2015, the Proniatyn site became the subject of scientific excursion of the international loess seminar «Loesses and Palaeolithic of Podillia». To clarify the age of the site, survey pit 5, located directly next to the main excavation, in the southern part of the site was expanded and deepened. The main goal of the work was to search for artifacts in the Horokhiv fossil pedocomplex (MIS 5), which is only slightly disturbed by deluvial-solifluctional processes. Two artifacts were found in the eluvial horizon of this complex, the third one was found in its humus horizon. Detailed analysis of the finds shows that the additional flint artifacts discovered in 2015 do not contradict the conclusion that technical, morphological and typological features of these three flints are completely identical to several thousand previously excavated flints from this site and represent the flake-blade Levallois industry. In general, all discovered artifacts from Proniatyn form a single monocultural complex of the site. Based on research conducted in 2015 is clearly established that the age of Proniatyn cultural horizon does not correspond to the age of deluvial-solifluctional strata, as previously thought, but is older than it. It is associated with the eluvial horizon of the Horokhiv fossil soil complex, the age of which is estimated at 112,0±11,2 ka and 106,7±11 ka according to TL-dating (the Palaeolithic site Yezupil I), 110±18 ka according to TL-dating and 102±16 ka according to OSL-dating (Palaeolithic site Mariampil I). Key words: Middle Palaeolithic, artifact, Mousterian, loess-palaeosol sequence, deluvial-solifluctional processes, Podillia.

MODELS TO PREDICT SLOPE LENGTH FROM OTHER WATERSHED ATTRIBUTES

Soil erosion by water is an extensive and increasing problem worldwide. Albeit, this problem has been recognized as a significant hazard in Iraq, yet the number of studies on this topic is very limited. Most of the models used for estimating soil erosion contain parameters for slope length factor (LS). A major constraint is the difficulty in extracting the LS factor. Accordingly, the current study was initiated with the main objective of deriving models to predict the slope length from relatively easy to measure basin characteristics with a reasonable accuracy. To achieve the above objective, standard methodologies were employed to describe 30 main basins with the upper part of Iraq in terms linear, areal and relief morphometric parameters. The majority of the delineated watersheds were characterized by having high slope lengths indicating lower drainage density and higher erosion rate. Linear and non-linear least squares techniques were applied to predict the slope length from other basin characteristics. Different indicators were used to test the performance of the proposed models and the approach was validated using K-fold procedure at independent basins. The results indicated that the 4-parameter regression model outperformed the remaining models of watershed slope length. The regressors of this model are bifurcation ratio, perimeter, and basin length and slope gradient.

A Pragmatic Slope-Adjusted Curve Number Model to Reduce Uncertainty in Predicting Flood Runoff from Steep Watersheds

The applicability of the curve number (CN) model to estimate runoff has been a conundrum for years, among other reasons, because it presumes an uncertain fixed initial abstraction coefficient (λ = 0.2), and because choosing the most suitable watershed CN values is still debated across the globe. Furthermore, the model is widely applied beyond its originally intended purpose. Accordingly, there is a need for more case-specific adjustments of the CN values, especially in steep-slope watersheds with diverse natural environments. This study scrutinized the λ and watershed slope factor effect in estimating runoff. Our proposed slope-adjusted CN (CNIIα) model used data from 1779 rainstorm–runoff events from 39 watersheds on the Korean Peninsula (1402 for calibration and 377 for validation), with an average slope varying between 7.50% and 53.53%. To capture the agreement between the observed and estimated runoff, the original CN model and its seven variants were evaluated using the root mean square error (RMSE), Nash–Sutcliffe efficiency (NSE), percent bias (PB), and 1:1 plot. The overall lower RMSE, higher NSE, better PB values, and encouraging 1:1 plot demonstrated good agreement between the observed and estimated runoff by one of the proposed variants of the CN model. This plausible goodness-of-fit was possibly due to setting λ = 0.01 instead of 0.2 or 0.05 and practically sound slope-adjusted CN values to our proposed modifications. For more realistic results, the effects of rainfall and other runoff-producing factors must be incorporated in CN value estimation to accurately reflect the watershed conditions.

Estimation of Base Flow by Optimal Hydrograph Separation for the Conterminous United States and Implications for National-Extent Hydrologic Models

Optimal hydrograph separation (OHS) uses a two-parameter recursive digital filter that applies specific conductance mass-balance constraints to estimate the base flow contribution to total streamflow at stream gages where discharge and specific conductance are measured. OHS was applied to U.S. Geological Survey (USGS) stream gages across the conterminous United States to examine the range/distribution of base flow inputs and the utility of this method to build a hydrologic model calibration dataset. OHS models with acceptable goodness-of-fit criteria were insensitive to drainage area, stream density, watershed slope, elevation, agricultural or perennial snow/ice land cover, average annual precipitation, runoff, or evapotranspiration, implying that OHS results are a viable calibration dataset applicable in diverse watersheds. OHS-estimated base flow contribution was compared to base flow-like model components from the USGS National Hydrologic Model Infrastructure run with the Precipitation-Runoff Modeling System (NHM-PRMS). The NHM-PRMS variable gwres_flow is most conceptually like a base flow component of streamflow but the gwres_flow contribution to total streamflow is generally smaller than the OHS-estimated base flow contribution. The NHM-PRMS variable slow_flow, added to gwres_flow, produced similar or greater estimates of base flow contributions to total streamflow than the OHS-estimated base flow contribution but was dependent on the total flow magnitude.

Sensitivity Analysis of Mountain Flash Flood Risk: Case of Licheng County in China

Flash flood is one of the most significant natural disasters in China, particularly in mountainous area, causing heavy economic damage and casualties of life. Accurate risk assessment is critical to an efficient flash flood management. There are more than 530,000 small watersheds in 2058 counties in China where flash flood should be prevented. In practice, with limited fund and different risk levels, the priorities of each small watershed for flash flood prevention and control are also needed for an efficient flash flood management. This paper, take Licheng county in China as an example, aims to give out these priorities for management. First, sensitive indexes are identified among index system, which includes 9 indexes based on underlying surface characteristics of small watershed in hilly region. Second, the range of each index and the rank division of each index for evaluation are determined. Based on the rank divisions for evaluation, the flash flood risk grade eigenvalue (H) is calculated by Variable Fuzzy Method (VFM ) using 1000 samplings generated by Latin hypercube sampling method. Third, the key sensitivity factors that affect flash flood risk grade eigenvalue (H) are assessed by two different global sensitivity analysis methods -- stepwise regression analysis and mutual entropy. Both results indicate that watershed slope (S) is the most sensitive factor; the second is antecedent precipitation index (CN); while other factors are slightly different sensitive in sequence. This study shows that stepwise regression analysis and mutual information analysis are appropriate for the sensitivity analysis of mountain flash flood risk. Finally, based on watershed slope (S), the priorities of flash flood prevention and control of 119 small watersheds in Licheng county are given out.

Analysis of Erosion Hazard at Gagakan Sub-Watershed, Blora District, Central Java Province, Indonesia

Availability of soil erosion data is crucial for recovering carrying capacity of a degraded watershed. This study aims to analyze the level of soil erosion hazard in Gagakan Sub-Watershed, located at the downstream of Solo Watershed. Slope steepness of this area vary from very steep at the upper part and flat at the downstream. The dominant land cover is teak forest which consists of young and old stands. The level of soil erosion hazard was calculated by USLE (Universal Soil Loss Equation) and then analyzed spatially using GIS (Geographic Information System). The degree of erosion hazard was classified into five classes, i.e very slight, slight, moderate, severe, and very severe. The results showed that erosion hazard level of Gagakan sub-watershed ranged from very slight to very severe. The dominant is very slight (69%), while the others classified as slight (11%), moderate (15%), severe (1%), and very severe (4%). The countermeasures of soil erosion should be focused on the area with severe and very severe level of erosion hazard.

Linking LiDAR with streamwater biogeochemistry in coastal temperate rainforest watersheds

The goal of this study was to use watershed characteristics derived from light detection and ranging (LiDAR) data to predict stream biogeochemistry in Perhumid Coastal Temperate Rainforest (PCTR) watersheds. Over a 2-day period, we sampled 37 streams for concentrations of dissolved C, N, P, major cations, and measures of dissolved organic matter quality (specific ultraviolet absorbance, SUVA254) and bioavailability. Random forest – classification and regression tree analysis showed that aboveground biomass and structure and watershed characteristics, inclusive of mean watershed slope and elevation, watershed size, and topographic wetness, explained more than 60% of the variation in concentration for most measured constituents. These results indicate this approach may be particularly useful for predicting stream biogeochemistry in small forested watersheds where fine resolution is needed to resolve subtle differences in forest biomass, structure, and topography. Overall, we suggest that the use of LiDAR in many of the small and remote watersheds across the Southeast Alaskan PCTR as well as other forested regions could help inform land management decisions that have the potential to alter ecosystems services related to watershed biogeochemical fluxes.

Estimation of Design Flood Hydrographs for Osun River at Iwo Control Station in Osun State, Nigeria

The unit and storm hydrographs for the catchment of Osun River at Iwo station Osun State, Nigeria were developed. Soil Conservation Service (SCS) and Snyder’s unit hydrograph methods were used to develop synthetic hydrographs for the catchment, while the SCS Curve Number method was used to estimate excess rainfall values from rainfall depth of different return periods. The peak storm flows obtained based on the unit hydrograph ordinates using convolution procedures determined by SCS for rainfall events of 10yr, 20yr, 50yr, 100yr and 200yr return periods for the catchment vary from 819.87 m3/s to 1681.34 m3/s, while those based on Snyder’s method for the catchment vary from 551.41m3/s to 1134.86 m3/s . The statistical analysis at 5% level of significance indicated that there were significant differences in the two methods. The analysis showed that the total peak flows for different return periods obtained from SCS method is higher than that of Snyder’s method by 33.16%. SCS method was recommended for use on the watershed since it incorporates most major hydrological and morphological characteristics of the basins like the watershed area, main channel length, river channel slope and watershed slope.