Abstract: This paper presents the results and findings from a
parametric study on the water surface elevation at upstream of bridge
constriction for subcritical flow. In this study, the influence of
Manning's Roughness Coefficient of main channel (nmc) and
floodplain (nfp), and bridge opening (b) flow rate (Q), contraction
(kcon) and expansion coefficients (kexp) were investigated on
backwater level. The DECK bridge models with different span widths
and without any pier were investigated within the two stage channel
having various roughness conditions. One of the most commonly
used commercial one-dimensional HEC-RAS model was used in this
parametric study. This study showed that the effects of main channel
roughness (nmc) and flow rate (Q) on the backwater level are much
higher than those of the floodplain roughness (nfp). Bridge opening
(b) with contraction (kcon) and expansion coefficients (kexp) have very
little effect on the backwater level within this range of parameters.
Abstract: This research was conducted in the Mae Sot
Watershed where located in the Moei River Basin at the Upper
Salween River Basin in Tak Province, Thailand. The Mae Sot
Municipality is the largest urban area in Tak Province and situated in
the midstream of the Mae Sot Watershed. It usually faces flash flood
problem after heavy rain due to poor flood management has been
reported since economic rapidly bloom up in recent years. Its
catchment can be classified as ungauged basin with lack of rainfall
data and no any stream gaging station was reported. It was attached
by most severely flood events in 2013 as the worst studied case for
all those communities in this municipality. Moreover, other problems
are also faced in this watershed, such shortage water supply for
domestic consumption and agriculture utilizations including a
deterioration of water quality and landslide as well. The research
aimed to increase capability building and strengthening the
participation of those local community leaders and related agencies to
conduct better water management in urban area was started by mean
of the data collection and illustration of the appropriated application
of some short period rainfall forecasting model as they aim for better
flood relief plan and management through the hydrologic model
system and river analysis system programs. The authors intended to
apply the global rainfall data via the integrated data viewer (IDV)
program from the Unidata with the aim for rainfall forecasting in a
short period of 7-10 days in advance during rainy season instead of
real time record. The IDV product can be present in an advance
period of rainfall with time step of 3-6 hours was introduced to the
communities. The result can be used as input data to the hydrologic
modeling system model (HEC-HMS) for synthesizing flood
hydrographs and use for flood forecasting as well. The authors
applied the river analysis system model (HEC-RAS) to present flood
flow behaviors in the reach of the Mae Sot stream via the downtown
of the Mae Sot City as flood extents as the water surface level at
every cross-sectional profiles of the stream. Both models of HMS and
RAS were tested in 2013 with observed rainfall and inflow-outflow
data from the Mae Sot Dam. The result of HMS showed fit to the
observed data at the dam and applied at upstream boundary discharge
to RAS in order to simulate flood extents and tested in the field, and
the result found satisfying. The product of rainfall from IDV was fair
while compared with observed data. However, it is an appropriate
tool to use in the ungauged catchment to use with flood hydrograph
and river analysis models for future efficient flood relief plan and
management.
Abstract: Flood wave propagation in river channel flow can be enunciated by nonlinear equations of motion for unsteady flow. It is difficult to find analytical solution of these non-linear equations. Hence, in this paper verification of the finite element model has been carried out against available numerical predictions and field data. The results of the model indicate a good matching with both Preissmann scheme and HEC-RAS model for a river reach of 29km at both sites (15km from upstream and at downstream end) for discharge hydrographs. It also has an agreeable comparison with the Preissemann scheme for the flow depth (stage) hydrographs. The proposed model has also been applying to forecast daily discharges at 400km downstream in the Indus River from Sukkur barrage of Sindh, Pakistan, which demonstrates accurate model predictions with observed the daily discharges. Hence, this model may be utilized for flood warnings in advance.
Abstract: This research was conducted in the Lower Ping River
Basin downstream of the Bhumibol Dam and the Lower Wang River
Basin in Tak Province, Thailand. Most of the tributary streams of the
Ping can be considered as ungauged catchments. There are 10-
pumping station installation at both river banks of the Ping in Tak
Province. Recently, most of them could not fully operate due to the
water amount in the river below the level that would be pumping,
even though included water from the natural river and released flow
from the Bhumibol Dam. The aim of this research was to increase the
performance of those pumping stations using weir projects in the
Ping. Therefore, the river analysis system model (HEC-RAS) was
applied to study the hydraulic behavior of water surface profiles in
the Ping River with both cases of existing conditions and proposed
weirs during the violent flood in 2011 and severe drought in 2013.
Moreover, the hydrologic modeling system (HMS) was applied to
simulate lateral streamflow hydrograph from ungauged catchments of
the Ping. The results of HEC-RAS model calibration with existing
conditions in 2011 showed best trial roughness coefficient for the
main channel of 0.026. The simulated water surface levels fitted to
observation data with R2 of 0.8175. The model was applied to 3
proposed cascade weirs with 2.35 m in height and found surcharge
water level only 0.27 m higher than the existing condition in 2011.
Moreover, those weirs could maintain river water levels and increase
of those pumping performances during less river flow in 2013.
Abstract: This research was conducted in the Lower Namkam
Irrigation Project situated in the Namkam River Basin in Thailand.
Degradation of groundwater quality in some areas is caused by saline
soil spots beneath ground surface. However, the tail regulated gate
structure on the Namkam River, a lateral stream of the Mekong
River. It is aimed for maintaining water level in the river at +137.5 to
+138.5 m (MSL) and flow to the irrigation canals based on a gravity
system since July 2009. It might leach some saline soil spots from
underground to soil surface if lack of understanding of the
conjunctive surface water and groundwater behaviors. This research
has been conducted by continuously the observing of both shallow
and deep groundwater level and quality from existing observation
wells. The simulation of surface water was carried out using a
hydrologic modeling system (HEC-HMS) to compute the ungauged
side flow catchments as the lateral flows for the river system model
(HEC-RAS). The constant water levels in the upstream of the
operated gate caused a slight rising up of shallow groundwater level
when compared to the water table. However, the groundwater levels
in the confined aquifers remained less impacted than in the shallow
aquifers but groundwater levels in late of wet season in some wells
were higher than the phreatic surface. This causes salinization of the
groundwater at the soil surface and might affect some crops. This
research aims for the balance of water stage in the river and efficient
groundwater utilization in this area.