Assignment 3

Question 1

a. You are undertaking a dynamic hydrographic survey in a small boat for a marina development. You are required to calculate the total draft correction including settlement and squat for the boat when underway and to also calibrate the echo-sounder to read the correct water depth at cruising speed by the Bar Check method. The following staff readings have been taken (at different locations for land and then water):

At the office;

Top of boat horizontally adjacent to transducer: 0.250 m

Transducer: 1.800 m

At the jobsite, Static in water;

Top of boat horizontally adjacent to transducer: 1.80 m

Water level: 2.650 m

Top of boat horizontally adjacent to transducer at cruising speed: 1.75m

At the job site, in water for Bar check;

Bar (depth) fixed 5m directly below the transducer towards the sea bed.

i. Calculate the static draft correction, the settlement and squat when underway, and calculate the adjusted echo sounder reading to read the correct water depth at cruising speed for the bar check.

ii. Based on the below diagram, mark out a non-GNSS position fixing method and pattern.

b. A GNSS base station set over a known PSM records an ellipsoidal height of 25.050m (uncorrected for antenna height), the antenna height is 1.45m and the AHD value of the PSM is 24.450m. At the time of hydrographic survey for the marina development, the vertical component from GNSS boat antenna receiver to water level is measured to be 2.45m. Reduce the following soundings to AHD:

Diagram below for illustration for 1(a)(ii) 

c. A rural stormwater channel requires a culvert design (only one RCP configuration is to be calculated, DO NOT CALCULATE RCBC configurations). The channel is approximately 7m wide and needs multiple pipes, you have a wide range of RCP’s on hand. 

The following design data has been provided:

Design Discharge Q50 = 9.0 m3/s.

Allowable outlet velocity = 4 m/sec.

Flood level = 61.1m

Invert level of channel at outlet = 60 m

Slope of culvert = 0.010 m/m

Allowable headwater depth = 2.0 m

Length = 25 m

Ke = 0.5

Question 2

a. A catchment drains to kerbing and channelling to a road that has a uniform longitudinal slope of -1.1%. The time of concentration calculates to be 15 minutes and the run-off coefficient C = 0.85. The minor storm is a 5 year ARI. Each sub-catchment is approximately rectangular (A = W x L). I = 80 mm/hr from IFD data for 5 year ARI, 15 minute duration. Determine the maximum permissible inlet pit spacing and subsequent pit spacing from bypass flow, given that the width of the sub-catchment is around 40 metres for a two lane road width of 7.9 metres, given Q = C.I.A.k for k in square metres. The roadway capacity is to be limited by the depths of flow below using Izzard’s equation (from Module 9) below. The flow rate and spacing of the inlet pits is related to the depth and spread of surface flow along the roadway and the pit capture efficiency is 60%. 

where F is 0.8 for a compound triangular section, ZG and ZP are 8.888% and 3% crossfall’s, nG and nP are Manning roughness coefficients for the gutter and pavement are 0.012 and 0.014 respectively, yG, yP and yC are the maximum depths of flow in the gutter and are 0.115, 0.075 and 0.000 for the gutter, pavement and crown of the road respectively and S0 is the absolute value of the longitudinal slope of the road.

b. In a stormwater network hydraulic design of a 60 m pipe length between two pits, the following data is provided:

Upstream pit surface level: 80.80 m

Downstream pit surface level: 80.5 m

Pit energy loss coefficient kw: 4.0

Minimum freeboard at pits: 150 mm

Minimum pipe cover: 400 mm

Pipe wall roughness ks: 0.06 mm

Flow rate Q: 60 litres per second

μ = 0.001139 Kg/ms

For a 300 mm diameter pipe, suitable for full-pipe flow, calculate upper and lower limit obvert levels for the pipe reach and the pipe gradient based upon the physical cover and slope of the total energy line.

Question 3

a. ‘As constructed’ plans, documents and files are supplied to local government authorities upon completion of civil works for land development. Discuss the survey methodology for undertaking ‘as constructed surveys’ (during the course of construction), including accuracies and the necessary relevant ‘as-constructed’ capture requirements for a sewage line in an urban subdivision, for provision for a typical local authority.

b. It is proposed to intersect two grade lines to fit a pedestrian walkway connecting two buildings, above a freeway. The distance between the two points is 200m and the reduced levels are as follows: Point 1 = 98.000m, Point 2 = 95.000m. Two successive grades of 1:80 (positive grade from point 1 to intersection point) and -1:40 (negative grade from intersection point to point 2) are proposed to intersect between the points. Calculate the reduced level of the intersection point and the distance of the intersection point from both points. Confirm and check the accuracy of your calculations.

Question 4

a. As part of the ground and feature modelling data collection stage of survey for the design of a road and small bridge, a bridge site survey is required to obtain sufficient information for design purposes. Describe the survey requirements and other relevant information to be obtained to aid in the design of the bridge.

b. It is proposed to construct an earth and rock filled dam across a major creek for irrigation of crops. The dam will abut either side of the stream (there is no by-wash, but there will be a drop inlet) and is 3 metes wide at the crest and batters down to the creek bed at 2h:1v ratio. (i) List and describe the types of surveys that may be required from the feasibility stage to final construction stage (there is no requirement for cadastral surveys or road surveys). (ii) Sketch an outline of the extent and location of any marks placed for setting out the dam, drop inlet, extent of the dam, control/recovery marks and benchmarks.