Melamchi Flood Analysis Using Drone Technology | Melamchi Flood | Drone Survey Carried out in Melamchi Flooding

Bhemathang -melamchighang section

Background

· Flood and landslide are frequent natural disasters of Nepal which occur in monsoon every year.

· These disasters annually claim thousands of lives and millions dollar of economic losses.

· Hydrology and meteorology department data shows heavy rainfall in this year monsoon relatively to previous ones.

· Heavy rainfall has caused flood and landslide all around the country.

· The biggest flood disaster of this year happened in 15^th June 2021, Melamchi-Helambu area of Sindhupalchowk district 60 km north-east from the Kathmandu..

Study Area

· Helambhu R- Municipality, Melamchi Municipality and Panchpokhari.

· Drone Survey : Indrawati and Melamchi River Basin, Sindhupalchowk.

· Land Slide prone area/ flood risk areas

· Major Risk Settlements: Nakote, Timbu Chanaute, Kiwul, Gyalthumg and Taramarang. and Melamchi Bazar.

Study Methodology

Technology Used During Field and Office Works

Drone Technology

Survey drones generate high-resolution orthomosaics and detailed 3D models of areas where human resources are not possible to reach.

Why Drone Survey in Disaster Management Project ?

Reduce field time and survey costs

Provide accurate and exhaustive data

Map otherwise inaccessible areas

Software Use

Agi-Soft: Drone Image Processing

Erdas imagine: Image Correction and Image Enhancement

Arc. GIS: Terrain Analysis and Image Analysis

Arc. Scene: 3-D Terrain Model Visualization

Summary Photograph of field visit.

Analysis

Change Pattern of Melamchi River After Flooding

-On 16 June, the Helambhu Rural municipality (Chowkphu, chusamani, Nakote, Fupkang, Kharchun, Chadan, Rival, Sarkathali, Ambathang, Dhuring, Timbu, Sene, Haldhe, Chasam, Kiwul, Chanaute, Gaylthumg and Taramarang settlements) and Melamchi municipality (Taramarang, Fatte, Kattike, Purano Bazar and Melamchi bazar) was hit by a heavy flash flood from two tributaries – the Melamchi and Indrawati rivers –

-damaged of 252 households in Helambhu and 291 households in Melamchi municipality along with heavy damage to the Melamchi water supply project while cutting off road access to several settlement.

River Pattern Change in Bhemathang Area

-The figure shows the location of Bhemathang area.

-It is clearly visualize that the left side of figure (date: 2020) shows less deposition of debris and right side (date: 2021,Aug 6) of the figure shows the heavy deposition of sediments in Bhemathang area after flood.

Bhemathang Before & after Flood

The above figure shows the location of Bhemathang area. It is clearly visualized that the left side of the figure (date: 2020) shows less deposition of debris and the right side (date: 2021, Aug 6) of the figure shows the heavy deposition of sediments in Bhemathang area after a flood

Maximum Source of Deposition is From Pemgdang Khola

After four days of study in the Bhemathang area, the source of deposition in Bhemathang is from the Pemdang river and the Melamchi river. The flow direction of the Pemdang river is from North -west to south whereas the Melamchi river is from North-East to South, these two rivers meet at Bhemathang.

It is clearly visualized that in the above picture, the flowing water of the Pemdang river is muddy, and the Malamchi river is crystal clear water. This concludes that the maximum source of debris deposition in Bemathang is from the Pemdang river.

Sediment Loss & Deposition in Bhemathang

Bhemathang river profile before & after Flood

Sediment Loss & Deposition Bhemathang - Melamchighang

Summary of Mass Balance

The above table shows a summary of the mass balance volume of the Melamchi flood. The sediments deposition and loss in the Bhemathang section is 17.59 mcm and 0.67 mcm, similarly the sediment deposition and loss in bhemathang to melamchighang section is 1.03mcm and 29. 11mcm.The sediments deposition and loss in melamchighang to melamchi bazar section is 51.85mcm and 18.95mcm. The net sediment deposite in drone surveyed area is 21.74mcm.