{"id":97,"date":"2013-03-27T19:24:15","date_gmt":"2013-03-27T19:24:15","guid":{"rendered":"http:\/\/weblab.open.ac.uk\/blog\/?p=97"},"modified":"2013-12-02T11:36:58","modified_gmt":"2013-12-02T11:36:58","slug":"river-observations-at-carding-mill-valley","status":"publish","type":"post","link":"http:\/\/weblab.open.ac.uk\/blog\/archives\/97","title":{"rendered":"River observations at Carding Mill Valley"},"content":{"rendered":"

Today Dave, Jim, Javi and Phil (from the FSC) took me to Carding Mill Valley and showed me the river observation and data collection activities that they do there with groups of students. We walked up the river to get a sense of the location, and Dave and Jim gave me a data collection worksheet that students currently use and walked me through the process of collecting a set of river observations. With secondary school groups they might repeat the observations up to ten sample sites as they walk back down along river, for primary students a similar set of observations would be made at fewer sites.<\/p>\n

Although a similar types of measures are made by different types of groups (i.e. primary, secondary, tertiary, etc.) the equipment used and number of data collection sites does vary. The following notes identifies the order and procedures involved in taking these measures, these would be repeated at each data collection site:<\/p>\n

Example data collected at one site<\/strong><\/p>\n

    \n
  1. Wetted perimeter (m)<\/em> [x1]: 1.67 meters<\/li>\n
  2. Width (m)<\/em> [x1]: 1.45 meters<\/li>\n
  3. Profile data<\/em> [x11]:\n
      \n
    1. Depth (cm)<\/em>: 14.5, 12, 16, 25, 21, 27, 30, 24.5, 20, 18, 13 centimeters<\/li>\n
    2. Bedload size (cm)<\/em>: 5, 3.4, 6, 6.3, 5.4, 9, 14, 8, 5.6, 12, 4.8 centimeters<\/li>\n
    3. Bedload roundness (class)<\/em>: 2, 2, 3, 2, 1, 2, 2, 3, 3, 2, 2, 3 Powers Index of Roundness<\/li>\n<\/ol>\n<\/li>\n
    4. Velocity [x3]<\/em>: 1.2, 0.8, 1.4 meters per second<\/li>\n
    5. Gradient<\/em>: 23 degrees<\/li>\n
    6. Notes<\/em>: There is a sharp bend to the right at horizontal angle of about 45 degrees, the left hand side bank shows signs of water erosion and there is some gravel deposited approx 10cm up the bank on that side, large boulder in the right hand side of the channel, approx 2m upstream.<\/li>\n<\/ol>\n

      Data collection procedure<\/strong><\/p>\n

      Wetted perimeter (m)<\/em> [x1]: At each site the groups start by measuring the wetted perimeter and width of the river. These are measured directly across the river. The wetted perimeter is a the length along the riverbed of a line that perpendicularly bisects the river. A chain is used to measure this. Starting by placing one end of the chain at one side of the river, the chain is laid out a few inches at a time along the riverbed until you reach the other side of the river. The end point on the chain is then held and the length of chain measured out is noted in meters.<\/p>\n

      Width (m)<\/em> [x1]: The width of the river is measured with a measuring tape. Like the wetted perimeter this is measured directly across the river. The width and wetted perimeter together outline the cross-section of the river at that data collection site.<\/p>\n

      Cross profile data<\/em> [x11]: The following three measures (i.e. depth, bedload size and bedload roundness) are done repeatedly across the river. Typically, the groups take measures at equal intervals across the river. For secondary school groups 11 data points are collected – 11 is an ‘easy number’ in that to identify the distance between each data point the students divide the river width at that point by the number of measures minus one. So in the case of 11 points the students would divide the river width by ten (e.g. river width = 1.45 meters, so make eleven measures starting 0 centimeters from one one side and work your way across to the other side i.e. at 14.5cm, 29cm, 33.5cm … 145cm from one side).<\/p>\n