The rapid evolution of Unmanned Aerial Vehicles (UAV) has been largely driven by its extensive deployment in surveillance, agriculture, forestry, archaeology, military operations, environmental monitoring, and other similar domains. Across majority of these applications, UAV serve as image capture platforms, relaying captured data to other UAV or ground stations. However, transmission of digital image through UAV channels remains susceptible to unauthorized access and a spectrum of deliberate or inadvertent security breaches. Digital Image Watermarking (DIW) has emerged as a promising solution for fortifying the security of digital image transmission within UAV frameworks. To address this issue, a secure digital image watermarking scheme using RDWT-SVD transform domain is proposed. At the sender node, an encrypted watermark (authentication or copyright information) is interleaved in the host digital image. The receiver node extracts the watermark and decrypts to validate the authenticity of the received image. A novel light weight symmetric cryptographic-based four-level encryption approach is proposed for encryption/decryption of the watermark for high UAV image security. This encryption technique utilizes chaotic map and XOR operation to ensure high security at minimal computational expense. Experimental evaluations demonstrate the effectiveness of the proposed scheme, showcasing high visual quality and robustness (with an average Peak Signalto-Noise Ratio (PSNR) of 42.93 dB, Average Structural Similarity Index (SSIM) of 0.99, Normalized Correlation (NC) of 0.99, and Bit Error Rate (BER) of 0.0014 calculated across 100 images captured by UAVs. Both subjective and objective analyses affirm the heightened security and computational efficiency of the proposed encryption scheme. Furthermore, the scheme exhibits resilience against various image processing attacks, as validated through comparative assessments against recent state-of-the-art approaches. The presented DIW framework holds promise for applications such as copyright protection.