Materials and method

The methodology approach mentioned in this study consists of four stages. The first stage is data collection of hydrographic data, hydrological records, bed material samples, and velocity measurements. The second stage is model preparation by mesh generation, model calibration, and verification using boundary conditions. The third stage is a model application to evaluate the morphological, hydrological changes, flooded land analysis, the current maximum conveyance capacity of the Rosetta branch. The fourth stage is the results and analysis of the three proposed rehabilitation scenarios’ impact on water surface profile, inundated land, and conveyance capacity as shown in Figure 1.

Study area

The study area covers approximately 155 km in the Rosetta branch of the Nile River in Egypt. Extending from Delta Barrage at Km 26 heading north reaching Shabrakhet gauge station at Km 181 downstream Elroda gauge station. Rosetta branch is considered a meandering channel whose sinuosity index is 1.5 and average channel width 122 m. The study area includes five water gauge stations and one control structure in addition to 5 drains discharging its effluent directly into the branch as shown in Figure 2.

Data collection

Hydrological data

Daily water level records of five water gauge stations (Elkhatatba, Abo Elkhawey, Zaywet Elbahr, Kafr Elzayat, and Shabrakhet) and flow discharge records of Delta Barrage were collected for the study. The average daily discharge of five drains (Elrahawey, Sabl, Eltahrer, Zawyet Elbahr, and Tala) was also collected. The collected data have a return period of 15 years from 2005 to 2020. The collected data revealed that the maximum flow discharge values are mainly recorded from June to August, while the minimum values are from November to January. The maximum recorded discharge was about 90 million m3/day during the year 2007, while the minimum discharge was 5 million.m3/day during the year 2005.

Hydrographic data

The hydrographic data consists of a Hydrographic survey of the study area bed level with a length of 155 km during the years 2020 and 2003. The hydrographic survey was carried out by the Nile Research Institute (NRI) of the National Water Research Center (NWRC) in Egypt.

Bed material samples and velocity measurements

Four velocities cross-sections were selected for model calibration and verification. The streamflow velocity was measured in the field. The first two were at km 37 while the second two were at km 140 from Elroda gauge. Also, five locations were chosen for bed material sample extraction at km (57,64,94,120, and 150) respectively from Elroda gauge where the average D50 was 0.35 mm and soil classification was fine to medium sand.