Flow Behavior of Boyong River as Revealed by Long-term Hydro-monitoring System

Boyong River is one of many rivers originating from Mt. Merapi, flows across three autonomy administrative of Sleman Regency, Yogyakarta City, and Bantul Regency. The river experiences flood in the form of lava flow several times, and the 1994 and 2010 occurrences were considered the biggest ones along with the river history. In line with the rapid development of information and communication technology, efforts to develop the early warning system due to the Mt. Merapi disaster have been implemented by the Hydraulic Laboratory of Gadjah Mada University 2006. This paper presents the study results of Boyong River flow behavior by analyzing the data obtained from the monitoring system. The Gemawang Weir at Boyong River was selected as the river control point understudy; those include the catchment boundary, the catchment characteristics, and the hydraulic features. Monitoring equipment consists of an automatic water level recorder (AWLR), the flow visualization using a Brinno camera, and the hydrophone monitoring system. The flow hydrograph characteristics and its corresponding sediment transport rate are considered two parameters for identifying the flow behavior. The results show that the precursive and recession times of the flood hydrograph are about 1-3 hours and 3.5-5 hours, respectively.

Geophysical investigation to assess condition of grouted scour hole : Old River Control Complex—Low Sill Concordia Parish, Louisiana

Geophysical surveys, both land-based and water-borne, were conducted at the Old River Control Complex‒Low Sill, Concordia Parish, LA. The purpose of the surveys was to assess the condition of the grout within the scour region resulting from the 1973 flood event, including identification of potential voids within the grout. Information from the ground studies will also be used for calibration of subsequent marine geophysical data and used in stability analysis studies. The water-borne survey consisted of towed low frequency (16-80 MHz) ground penetrating radar (GPR), whereas the land-based surveys used electrical resistivity and seismic refraction. The GPR survey was conducted in the Old River Channel on the upstream side of the Low Sill structure. The high electrical conductivity of the water (~50 mS/m) precluded penetration of the GPR signal; thus, no useful data were obtained. The land-based surveys were performed on both northeast and southeast sides of the Low Sill structure. Both resistivity and seismic surveys identify a layered subsurface stratigraphy that corresponds, in general, with available borehole data and constructed geologic profiles. In addition, an anomalous area on the southeast side was identified that warrants future investigation and monitoring.

Collapses on the riverbank: what happened to the Lower Yellow River?

<p>Riverbank collapses frequently occur in the lower reaches of the Yellow River, China, which result in a great loss of farmland and significant hydro-morphological evolution in the channel. A combination of field investigation and remote sensing analysis was conducted to understand the current status of riverbank collapse in the Shandong Reaches of the lower Yellow River. The results show that the planar failure and upward-concave collapse were the main types of river failures in these reaches. Taking the Jiyang section as an example, the average lateral dynamic displacements in the Jiyang section were 2.8 and 11.4 m, the retreat areas were 248.8 and 835.0 m<sup>2</sup> and the maximum lateral dynamic displacement were 7.4 and 26.0 m during the periods 3/31/2016-4/18/2017 and 04/18/2017-5/10/2018, respectively. Factors such as the soil properties, upstream river-control works, and channel bends may change the probability of downstream riverbank collapse. Building materials that are effective, low-cost and environmental friendly, and easy to use, are anticipated in the river management projects to protect the riverbanks and improve the ecological environment in the study area.</p>

Evaluation of the Floodplain Farming of the Settlements of Nagykunság Based on the First Cadastral Survey

River control was perhaps the most significant form of anthropogenic environmental intervention in the Carpathian Basin, and in recent decades it has been the focus of considerable attention in the scientific community. However, in order to be able to evaluate this intervention, we need to know more about the floodplain management before the river regulations. In this essay, I provide data concerning the eighteenth-century floodplain management, on the basis of the first cadastral survey documents. According to Klára Dóka and other researchers, the settlements of the region along the Tisza River were in crisis in the early nineteenth century because the floodplain farming system was not adequate to sustain the growing population. However, they based this conclusion on sources concerning population growth, and they did not substantiate their essential contention concerning overpopulation with accurate data on production and consumption. I have sought to determine whether there really was an overpopulation crisis in Nagykunság at the end of the eighteenth century. The main question concerns the relationship between production and needs. The next question is whether the farmers had excess grain which they could take to markets. In other words, was the floodplain farming system profitable? My research constitutes a contribution to the debate between Bertalan Andrásfalvy and Miklós Szilágyi on floodplain management. The first cadastral survey documents contain detailed and reliable data on the management of the settlements, and I contend that they are more accurate and useful than the tax censuses which were compiled at the same time. The first step in the research was to establish the average annual consumption of the population. According to the data of the cadastral survey, production exceeded the needs of the population in each settlement, and the value of the production surplus covered the tax burdens. Wheat had a marketable share of the yield, come to 30–40 percent of the total. Assuming that livestock breeding was even more advantageous, one could contend that the floodplain farming system was profitable. However, natural resources are distributed disproportionately as a result of property relations. In Nagykunság, this found its most dramatic embodiment in the redemptus-irredemptus contrast. There were several events in the late eighteenth century, such as the construction of the Mirhó dam and migration to Bácska, on the basis of which researchers have inferred that the floodplain farming system was in crisis, but the cadastral survey suggests otherwise.

Decadal-Scale Variations of Thalweg Morphology and Riffle–Pool Sequences in Response to Flow Regulation in the Lowermost Mississippi River

The lowermost Mississippi River (LMR) is one of the largest deltaic systems in North America and one of the heavily human-manipulated fluvial river systems. Historic hydrographic surveys from the mid-1900s to the early 2010s were used to document the thalweg morphology adjustments, as well as the riffle–pool sequences. Extensive aggradation was observed during 1950s to 1960s, as the Atchafalaya River was enlarging before the completion of the Old River Control Structure (ORCS). Following the completion of the ORCS, reductions in sediment input to the LMR resulted in net degradation of the thalweg profile patterns since the mid-1960s except for the 1992–2004 period. Different flood events that supplied sediment might be the cause of upstream aggradation from 1963–1975 and net aggradation along the entire reach from 1992–2004. Furthermore, the change pattern of thalweg profiles appear to be controlled by backwater effects, as well as the Bonnet Carré spillway opening. Results from riffle–pool sequences reveal that the averaging Ws ratios (length to channel width) are 6–7, similar to numerous previous studies. Temporal variations of the same riffles and pools reveal that aggradation and degradation might be heavily controlled by similar factors to the thalweg variations (i.e., sediment supply, backwater effects). In sum, this study examines decadal-scale geomorphic responses in a low-lying large river system subject to different human interventions, as well as natural flood events. Future management strategies of this and similar river systems should consider recent riverbed changes in dredging, sediment management, and river engineering.