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Content:
Vol. 11. No. 1 Spring 2011
Vol. 10. No. 2 Fall 2010
Vol. 10. No. 1 Spring 2010
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9, No.2
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9, No.1 Spring 2009
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A Method for Extracting Stream
Channel Flow Paths from LiDAR Point Cloud Data
Danny L. Anderson1 and Daniel P. Ames2*
Abstract:
Traditional methods of delineating stream channel networks use
gridded raster elevation data. Direct use of LiDAR point clouds,
without first creating a raster or grid, could improve efficiency
and accuracy. This paper reports the development, and demonstration
of a method of delineating stream channels directly from LiDAR point
cloud data without the intermediary step of interpolation to a
raster or grid. This method, termed “mDn”, is an extension of
the D8 method that has been used for several decades with gridded
raster data. The method divides the region around a starting point
into sectors, using the LiDAR data points within each sector to
determine an average slope, and selecting the sector with the
greatest downward slope to determine the direction of flow. An
algorithm was developed and implemented in ArcVew’s Avenue scripting
language. Three adjustable parameters allow fine tuning: radial
resolution, angular resolution, and maximum course change. A case
study area was selected just north of Redfish Lake, Idaho, at the
Fishhook Creek inlet. High resolution aerial photography was used to
trace the creek for a reference stream. An mDn delineation, a
TauDEM delineation, and other common stream delineations were
compared with the reference stream, by calculating sinuosity and
root mean square error. Although, the TauDEM delineation yielded a
higher sinuosity than the mDn delineation, sinuosity of the
mDn delineation more closely matched that of the reference
stream than either the TauDEM method or the existing published
stream delineations. Stream channel delineation using the mDn
method yielded the smallest root mean square errors.
Keywords: LiDAR; Point Cloud; Streams; Channels; Delineation.
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Groundwater Quality and
Vulnerability Mapping of an Unconfined Coastal Aquifer
S.
Sathish and L. Elango
Department of Geology, Anna University, Chennai, Tamil Nadu, India – 600
025.
elango@annauniv.edu,
elango34@hotmail.com
and
s.sathish.au@gmail.com
Abstract:
Groundwater quality mapping is very essential to identify regions where
groundwater is suitable for various uses. A study of the vulnerability of
groundwater for pollution in a region is required as it will provide
information for taking precautionary measures. Groundwater is being
extensively used for domestic purposes in the region south of Chennai,
India. The present study was carried out with the objective of preparing a
groundwater quality map and vulnerability map of the south Chennai coastal
aquifer. Groundwater samples from fifty representative wells distributed
over the entire area were collected and analyzed for electrical conductivity
and major ions. Based on the recommended limits of these parameters for
domestic use the area was divided into different zones. A spatial index was
assigned for these physio-chemical data layers showing groundwater with
good, moderate and poor quality and these layers were integrated by overlay
analysis using ArcGIS. From this overlay analysis, the groundwater quality
and vulnerability map was prepared. By superimposing all the layers based on
quality index, the vulnerability of groundwater was determined periodically.
Finally, the periodic vulnerability index was overlaid and vulnerability map
of this unconfined aquifer was represented by means of relative index value.
The groundwater quality map of the region can be used as a tool for suitable
and efficient management of groundwater by regulating pumping from the poor
quality zone. The groundwater quality mapping should be periodically carried
out as this aquifer is under stress and bounded by surface water bodies of
poor quality on all sides.
Key
words: hydrogeology, overlay analysis, special index, vulnerability
index, Chennai, India
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Sudies on Major Ion Chemistry
and Hydrogeochemical Processes of Groundwater in Port Harcourt City,
Southern Nigeria
H. O Nwankwoala and G.J Udom
Department of
Geology, University of Port Harcourt, P.M.B 5323, Choba, Port Harcourt,
Nigeria.
Abstract:
Of recent, the rapid deterioration of groundwater quality in Port Harcourt,
Southern Nigeria due to unregulated exploitation resulting from increasing
growth in the oil and gas production activities has become a major concern.
The predisposition of groundwater to pollution and the realization of its
serious health and economic consequences demand knowledge of the ambient
groundwater quality and of the processes leading to an improved
understanding of the groundwater in the area. Groundwater samples were
collected from eighteen (18) representative boreholes spread over the Port
Harcourt City. This was done to assess and determine the geochemical
processes occurring within the aquifer systems using groundwater chemistry
and ionic ratios. Properties such as electrical conductivity, pH and major
ion concentrations, such as Ca, Mg, Na, K, Cl, HCO3, and SO4,
of groundwater were taken into consideration. Concentrations of these
cations and ions in the groundwater systems of the area vary spatially and
temporally. Abundance of these ions are in the following order: Ca > Mg >Na
> K = HCO3 > Cl > SO4 > NO3. Ca - Mg - HCO3
and Ca- Mg- SO4- Cl are the dominant hydrochemical facies
of the study area. Results show that ion-exchange processes, carbonate and
silicate weathering are responsible mechanisms for the groundwater chemistry
of the area. Hydrochemical indices (Mg/Ca, Cl/HCO3 and Cation
Exchange Values (CEV) generally indicates low- salt inland waters, with
minimal marine influence. The hydrochemical evidence reveals the importance
of recent management decisions (reduced exploitation/controlled pumping) in
determining the evolution and distribution of groundwater salinity within
the aquiferous zones. This framework, as the study observes, will lead to
improved understanding of the hydrochemical characteristics of the aquifer
systems of the area.
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Assessment of Soil Loss Using
WEPP Model and Geographical Information System
A. Landi1,
A.R. Barzegar*, J. Sayadi and A. Khademalrasoul
Dept. of Soil Science, College of Agriculture, Shahid Chamran University (SCU),
Ahwaz, Iran
*
Corresponding author, former professor of SCU, email:barzegar.ar@gmail.com
Abstract"
Severe soil
erosion has generally been regarded as a major cause of land degradation in
arid and semi arid regions. A quantitative assessment of soil loss intensity
is still scanty for developing appropriate soil erosion control measures in
these regions. This article used the combined Water Erosion Prediction
Project (WEPP) and Geographic Information System (GIS) models to estimate
the average soil loss in the Halahijan watershed in Khuzestan Province, one
of the priority areas for soil erosion control in Iran. Also, the sediment
yield estimated by the WEPP was compared with that estimated by Modified
Pacific Southwest Interagency Committee
(MPSIAC) model. The MPSIAC model is used to estimate erosion yield and
erosion intensity using nine factors consisting of, geological
characteristics, soil, climate, runoff, topography, vegetation cover, land
use and present soil erosion. Results indicated that
the soil loss estimated by the WEPP model ranged from 15.10 to
28.20 Mg ha-1 yr-1 with an
average soil loss of 21.8
Mg ha-1
yr-1
in the study area. The soil loss estimated by WEPP model was highly
correlated with data estimated by MPSIAC (R2 = 0.97). The soil
erosion in this region can be attributed to rainfall intensity (which ranged
from 16 to 88 mm hr-1), and high surface runoff (which ranged
from 48562 to 80963 m3). Results also revealed that the WEPP
model is suitable for estimating soil loss in complex watersheds.
Keywords:
Modeling, WEPP, GIS, Soil erosion, Watershed.
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Abhijit Mitra,
Kunal Mondal and Kakoli Banerjee*
Department of Marine Science, University of Calcutta, 35 B.C. Road,
Kolkata-700 019, West Bengal, India
*Corresponding
author: E-mail:
banerjee.kakoli@yahoo.com
Abstract:
The lower stretch of Gangetic delta in the Indian sub-continent is noted for
its rich mangrove biodiversity, natural calamities, and
livelihood-supporting matrix of millions of people and is the only mangrove
base of Royal Bengal tiger (Panthera tigris tigris) in the planet
Earth. The present trend of industrialization, urbanization and construction
of barrage in the upstream zone has changed the landscape of the deltaic
complex and the characteristics of the aquatic sub-system have also changed
accordingly. This ecosystem offers an ideal site to study a number of
physico-chemical parameters in relation to changing scenario of the region.
The presence of heavily populated cities of Kolkata, Howrah and the Haldia
industrial belt on the bank of the Hooghly estuary has made the mighty River
Ganga highly vulnerable to anthropogenic stress. Spatial and tidal
variations of important physico-chemical parameters in the Hooghly estuarine
stretch of Gangetic delta complex were studied during the summer month
April, 2008. The water quality reflects the impact of Bay of Bengal (sea)
water almost on all the variables as revealed from the significant
difference of parameter values in high and low tides (except surface water
temperature and potassium). The 12 selected stations from the upstream to
downstream regions exhibited uniformity with respect to surface water
temperature. Significant spatial variations (at 5% level of significance)
were observed with respect to parameters like surface water salinity, pH,
alkalinity, DO, BOD, COD, NO3, PO4, SiO3,
extinction coefficient, SO4, Na, K, Cl and total nitrogen. Along
with tidal influences, the anthropogenic factors contributed by the adjacent
cities and towns exert a regulatory influence on parameters like BOD, COD,
NO3, PO4, extinction coefficient, SO4 and
total nitrogen.
Keywords:
Duncan
analysis, physico-chemical parameter, spatial variation, tidal condition,
Hooghly estuary
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JoSHJournal
of Spatial Hydrology
ISSN: 1530-4736