Says recommendation proposed is vague, needs reworking with actual facts & figures
MARGAO
A consultancy firm Terra Hydrotech Solutions engaged by the Benaulim panchayat has disputed the findings of the Water Resources Department (WRD) on the question of flooding in the low-lying and water catchment areas of Benaulim and adjoining area in the event the western bypass passing through Benaulim is not built on stilts.
In fact, the firm has concluded that the WRD report on flooding at Benaulim is based on insufficient data and that the methodology used to analyse the draining in the study area is rudimentary.
The firm has further stated in its report submitted to the Benaulim village panchayat, which is now relied by the panchayat to make a strong case before the High Court in support of its plea to build the bypass on stilts, that the recommendation proposed by WRD Chief Engineer is very vague and needs to be reworked with actual facts and figures, considering the right discharge points of Sal River at Khareband.
With the Goa government rejecting the demand for bypass on stilts by increasing the number of culverts along the stretch, the firm has pointed out that the proposed elevated structure for a small stretch will cause water-logging due to the damming effect and hence is a poor solution.
“If reworked, the figures will definitely be very higher than that stated in the report and the actual cause of the flooding can be delineated and real time solutions for mitigation of this situation can be delivered,” the firm stated in its report.
Doing a review of the study report and recommendation on the proposed National Highway Bypass passing through Benaulim prepared and submitted by Chief Engineer, Water Resources Department, Porvorim Goa and presented to the Member Secretary, Goa State Biodiversity Board, the firm has said WRD has prepared the report based on insufficient base data and information.
Saying the WRD report assumes values of the intensity of rainfall, slope of the river, type of soil, depth of the river and, flow and discharge rate of the river without providing any reference for the information.
Further pointing out that the entire catchment area has not been considered in the report, the firm stated that in the theoretical calculation presented in the report, the catchment area is assumed to be 55 sq km up to the wholesale fish market. However, the flooding problem is prevalent in the entire Benaulim catchment area up to Kharebandh which is two km downstream from the wholesale fish market. Hence, the agency has recommended to recalculate the catchment area to accommodate the entire area contributing to the flooding situation near Kharebandh and Benaulim and to rework the calculations for discharge at river outlet point near Kharebandh.
Saying there is no indication in the report of any ground survey, field measurements and sampling, it further pointed out there’s no demarcation of the flood plain detention basin and traditional openings on the catchment delineation map shown in the report.
On the maximum flood levels, the agency has pointed out that the Hydrology of River Sal makes no mention of the maximum height and average height of the floods. “These levels are important to assess the area currently impacted due to flooding, the area which may be impacted due to flooding after the construction of the highway as well as determining the height of the culverts,” the firm stated.
Saying the existing constrictions from the wholesale fish market to the southern boundary of Benaulim has not been considered in the WRD study report, the agency said building the highway along or close to the narrow points in the river where the channel width decreases, can have a significant impact on the flow of water and sediment transport, as well as the hydrology, ecology, and human activities within the river basin.
Referring to the absence of flood modeling in the WRD report, the agency said a flood modeling report is a technical analysis of flood behaviour using computer models. It typically includes a detailed analysis of flood hydrology, hydraulic modeling of river channels and floodplains, impact of the proposed project i.e western bypass highway and an evaluation of flood mitigation measures such as installation of culverts along the highway.
