STUDY MORPHOLOGICAL CHANGES IN KARAJ RIVER AND THE ENVIRONMENTAL EFFECTS OF WATER RESOURCES DEVELOPMENT, RIVER ENGINEERING, AND GRAVEL/SAND MINING PROJECTS

Rivers and streams are completely dynamic systems, and their location,
shape, and other morphological characteristics are continuously changing over
time. In addition to water resources development projects and river management
programs that are factors affecting rivers, gravel mining sites are also considered
one of the most important factors that cause changes in rivers morphology
through improper mining and consequently disturbing the sediment balance.
Various river training activities over recent years on Karaj River have imposed
significant morphological changes in the river system. These changes have
resulted in disruption of the natural flow patterns of the river and destruction of
riverbed and river banks in some reaches of the river. This research attempted to
analyze the adverse effects of those projects on Karaj River morphology. In this
research, the development of hydraulic-sediment models to assess changes in
flow conditions, sediment transport, and also possible morphological changes in
Karaj riverbed due to river channelization, building Alborz Lake and artificial
recharge was carried out through field visits, collecting information and available
reports and maps. The two-dimensional HEC-RAS 5.0.3 and one-dimensional
HEC-RAS 4.1 models were used to simulate flow and sediment, respectively. In
these modelings, three hydraulic scenarios were used to investigate the flow
status in 3 modes: base mode (without using any projects), channelization area,
and artificial recharge area whose results are presented in detail in the report.
Some problems were backwater flow upstream of the Alborz Lake due to
inadequate capacity of intake structure and the constriction situation in result of
river channelization, significant energy losses at channelized river mouth which
cause water to return to upstream and flood spreading on, turbulence and
rotational currents due to inappropriate angle of connecting the river canal with
freeway bridges. These problems may have a significant impact on the hydraulic
flow and sediment of the river not so far away, especially within the bridges area.

STUDY MORPHOLOGICAL CHANGES IN KARAJ RIVER AND THE ENVIRONMENTAL EFFECTS OF WATER RESOURCES DEVELOPMENT, RIVER ENGINEERING, AND GRAVEL/SAND MINING PROJECTS Keywords:

Morphology , Karaj River , Sand and gravel , River Training , Sediment , Erosion