Hydraulic Energy Dissipators - A Review
Hydraulic Energy dissipators are devices to protect downstream areas of basin from erosion by reducing the velocity of flow up to an acceptable limit. The stilling basins are transition structures fabricated to dissipate excess energy confined by flow with high velocity at the outlet of conduit or tunnel so that the flow beyond the basin does not threaten the firmness of bed and banks of downstream channel in structures like culvert spillways, canal, etc. from scouring. Henceforth proper attention needed by hydraulic engineers for t he design of energy dissipators so as to obtain optimum energy dissipation at outlet. The type of stilling basin most suitable at a particular location mainly depends upon initial velocity of flow and initial Froude Number. This paper describe about the different type of energy dessipators with different appurtanances used in hydraulic structures for protection work.
ANALYSIS OF BAFFLE WALL GAP IN THE DESIGN OF STILLING BASIN MODEL
This paper investigates the gap of baffle wall in stilling basin design for the enhancement of energy dissipation in order to protect the downstream structures from excessive scouring. Experiments have been carried out by keeping the baffle wall at same location for Froude numbers 3.85, 2.85 and 1.85 to evolve the new stilling basin model by changing the gap beneath the wall above the basin. Performance of outlet basins having baffle wall of at same location with varying the gap were evaluated based on dimensionless number called as performance index (PI), which is the ratio of grains Froude number to scour index. Higher values of PI indicate better performance of the basin. It is concluded that by placing the appropriate baffle wall size at suitable location with proper gap, the efficiency of basin increases.
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.