(SEM VI) THEORY EXAMINATION 2023-24 RIVER ENGINEERING

KCE062 – River Engineering (B.Tech Sem VI)

The answers are written in simple, clear, humanized language (not short points) and are prepared strictly according to the uploaded question paper (both pages).
Reference: Uploaded Question Paper 

KCE062-RIVER-ENGINEERING

SECTION A

Attempt all questions in brief (2 × 10 = 20 marks)

(a) How are rivers formed?

Rivers are formed mainly due to precipitation such as rainfall or snowfall. Water flows downhill under gravity, eroding soil and rocks. Over time, small streams join together, forming larger channels that develop into rivers.

(b) What are the features made by a river in a flood plain?

In a flood plain, a river forms features such as meanders, oxbow lakes, levees, point bars, flood channels, and natural embankments. These features develop due to lateral erosion and deposition during floods.

(c) What do you mean by the meander river system?

A meander river system is a river pattern characterized by sinuous curves or bends. It develops in flat areas where the river erodes its outer banks and deposits sediment on the inner banks.

(d) Draw the figure of braided river.

A braided river consists of multiple inter-connected channels separated by sand bars and islands. (In exams, a neat sketch showing multiple channels is expected.)

(e) What is good ecological restoration?

Good ecological restoration is the process of bringing back the natural structure, function, and biodiversity of a river system while maintaining balance between human needs and environmental sustainability.

(f) List out the purpose of a groyne.

A groyne is used to protect river banks from erosion, control river flow direction, and improve navigation conditions by guiding water away from vulnerable banks.

(g) How do you calculate bank height ratio?

Bank height ratio is calculated as the ratio of bank height to the maximum depth of flow. It helps in assessing channel stability.

(h) What are the limitations of bio-engineering techniques?

Bio-engineering techniques depend heavily on vegetation growth and climatic conditions. They are less effective during high floods and require time to develop full strength.

(i) Write the categories of river training works.

River training works are classified into high water training works, low water training works, and medium water training works, depending on the flow conditions they address.

(j) Draw the figure of launching apron.

A launching apron is a protective layer of stones placed at the toe of embankments to prevent scouring. (A neat labeled sketch is expected in exams.)

SECTION B

Attempt any three (10 × 3 = 30 marks)

(a) Difference between aggrading and degrading rivers

An aggrading river deposits more sediment than it carries, resulting in a rising riverbed. This occurs when sediment supply is high or flow velocity is low.
A degrading river erodes its bed due to higher flow velocity or reduced sediment supply, causing lowering of the riverbed. Aggradation leads to flooding risk, while degradation can expose foundations of structures.

(b) Formation of components of a meander river system

A meander river system consists of bends, pools, riffles, cut banks, and point bars. These components form due to secondary currents, which cause erosion at outer bends and deposition at inner bends. Over time, bends migrate and may form oxbow lakes.

(c) Methods of form-based restoration technique

Form-based restoration focuses on restoring natural river geometry. Techniques include re-meandering straightened channels, reshaping banks, creating flood plains, and stabilizing bed profiles. These methods enhance ecological balance and channel stability.

(d) Natural channel design phases

Natural channel design involves assessment of watershed conditions, understanding river morphology, designing stable channel dimensions, implementing restoration measures, and continuous monitoring. A flow chart showing sequential steps is usually drawn in exams.

(e) Number of spurs to control one side of stream bank

The number of spurs depends on spacing, which is generally 1.5 to 2 times the spur length projected along the bank.
Given bank length = 150 m and spur length = 10 m, suitable spacing ≈ 15–20 m.
Thus, approximately 8 to 10 spurs are required.

SECTION C

Attempt any one (10 marks)

(a) Controlling factors of river morphology

River morphology is controlled by climate, discharge, sediment load, geology, slope, vegetation, and human activities. Climate influences runoff, sediment load affects channel shape, and human interventions like dams and embankments alter natural river behavior.

(b) Structure of a river

A river structure consists of source, upper course, middle course, lower course, channel, banks, flood plain, and mouth. In the upper course, erosion dominates; in the middle course, transportation is significant; and in the lower course, deposition is dominant.