Seasonal Flow Characteristics of Kandla Creek Through In-Situ Measurements

Abstract

The measurement of tidal stream discharge is a complicated assignment in complex flow conditions that may be occasional or seasonal. The efficient discharge measurement in tidal streams is required with accurate real-time measurements over a longer-period. The discharge of tidal streams is computed as the product of the cross-sectional area and mean velocity. At present, the data on the discharge in tidal creeks and its behavior over time of the ingress of tide (i.e., rising or falling tide) which are seasonal along the Indian coast is inadequate, the understanding of which is considered in the present paper. This study has been carried out with the interest of exploring the seasonal flow pattern in the Kandla creek, Gulf of Kutch, Gujarat. The seasonal, temporal and spatial variation of Kandla Creek discharge of both vertical and lateral distributions of velocity was carried out by repetitive measurements by moving boat method throughout the 8 days of measurement during daylight of 10 to 12 hours a day. The magnitude and direction of the velocities relative to the boat were measured throughout the cross sections (east to west and/or west to east) at two locations (Location-1: North end of the Kandla creek and Location-2: South (near the creek mouth), by downward looking Acoustic Doppler Current Profiler (ADCP) equipment fixed at the side of the measurement vessel/boats with known draft and headings. The measurements were made at about 94 vertical traverses at each cross section. As soon as one traverse completion (left to right), the opposite side (right to left) of the creek traverse was measured for comparison. The maximum net discharge was recorded around 920 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /sec at Location-1 and around 1900 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /sec at Location-2, both during pre-monsoon with the ebb tide. During monsoon and post-monsoon season, the net discharge is observed during flood tide with relatively lesser magnitude than during the pre-monsoon ebb tide. The results on the discharge measurement confirm that the ebb tide is dominant during the pre-monsoon and the flood tide is dominant during the monsoon and post-monsoon seasons.