Remote Sensing Applications: Agriculture, Forestry, Water & GLOF
Idea in plain words
Agricultural Monitoring: Crop type identification, acreage estimation, crop vigor tracking (NDVI), and soil moisture estimation.
Exam tip
High-yield exam topic (Very High).
Explanation
Remote sensing provides irreplaceable monitoring capabilities across the fragile Himalayan ecosystem of Nepal. Optical satellite imagery cannot penetrate monsoon clouds; Synthetic Aperture Radar (SAR, Sentinel-1) penetrates rain and clouds to delineate flood boundaries across the southern Terai plains in real time. In high mountain regions, multitemporal satellite archives track expanding moraine-dammed glacial lakes, detecting terminal moraine dam instability and calculating downstream flood wave arrival times to protect downstream villages.
Key points
- Forestry Applications: Deforestation tracking, forest fire scar mapping, timber biomass estimation, and canopy height modeling.
- Hydrology & Flood Mapping: Delineating surface water bodies using Normalized Difference Water Index (NDWI), monitoring flood inundation extents via SAR imagery.
- Cryosphere & GLOF Monitoring in Nepal: Tracking Himalayan glacier retreat, mapping expanding supraglacial lakes (e.g., Tsho Rolpa, Imja Lake) to mitigate catastrophic outburst floods.
- Urban Planning: Monitoring urban sprawl, tracking impervious surface expansion, and analyzing urban heat island (UHI) effects using thermal infrared bands.
Example
Example
Monitoring Imja Glacial Lake in the Everest region: satellite image analysis revealed the lake surface expanded from 0.03 km² in the 1960s to over 1.3 km², leading to engineered lake lowering interventions.
Code examples
/*
Key Remote Sensing Spectral Indices:
1. Normalized Difference Vegetation Index (NDVI):
NDVI = (NIR - Red) / (NIR + Red)
(Values > 0.4 indicate dense green vegetation)
2. Normalized Difference Water Index (NDWI - McFeeters):
NDWI = (Green - NIR) / (Green + NIR)
(Values > 0 indicate open water bodies; suppresses vegetation)
3. Normalized Burn Ratio (NBR - Fire Scars):
NBR = (NIR - SWIR) / (NIR + SWIR)
*/
Exam questions
- [10 Marks] Explain how remote sensing is applied in Nepal for monitoring Glacial Lake Outburst Floods (GLOFs) and mapping flood inundation using Synthetic Aperture Radar (SAR).
- [8 Marks] Formulate the mathematical equations and explain the physical logic behind NDVI (Vegetation Index) and NDWI (Water Index).