From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

We often hear that floods are getting worse everywhere, but there is rarely any actual data supplied to prove it. Instead all we get is “proof” from  climate models.

Here, a highly detailed study of one river basin in India  concludes that floods are not increasing:

Abstract

With increased awareness and discussions about climate variability and climate change, backed up by several global-regional climate circulation-prediction models, it is often said that hydrological extremes are increasing. The present study analyzed the historical floods in Krishna River Basin (KRB) using observed streamflow and precipitation records along with published reports, including news articles, to corroborate, “are the floods increasing in KRB”?

The methodology involved quantitative and qualitative analysis of floods in KRB at the subsystem scale (K1 to K12). The quantitative analysis involved i) Development of unregulated flow series through hydrological modelling, ii) Frequency analysis of unregulated flows and precipitation, iii) Threshold selection for defining the small, medium, and large floods, iv) Identification of flood events in observed streamflow series and v) Identification of causal rainfall and its relationship with flood peak.

The qualitative analysis focused on published reports and news articles to discover multiple aspects of flood characteristics and losses. 

The study concluded that floods are neither increasing nor decreasing for most subsystems of KRB except K7 (Lower Krishna Basin), where floods are decreasing.

Cyclic patterns analogous to Noah and Joseph effect are seen in the case of small floods for all the subsystems except K7, whereas single-year extremes affecting the entire series similar to Noah and Joseph erratic behaviour have been observed in medium and large floods except the K12 subbasin (Munneru Basin). The study confirms that qualitative analysis cannot determine the trend in floods as every event in the historical record is uniquely described, covering different dimensions ranging from various flood characteristics, losses, short and long-term impacts.

This study can provide a guideline to identify changes in floods, especially in basins with altered hydrologic regimes. This shall provide crucial information to the administrators to restructure and develop ameliorative policies for flood management.

https://www.sciencedirect.com/science/article/pii/S2666592123000677