DRAINAGE CLASSIFICATION & RECLASSIFICATION

Transcription

1 DRAINAGE CLASSIFICATION & RECLASSIFICATION December 9, 2016 ARCHITECTURE + ENGINEERING + ENVIRONMENTAL + PLANNING

2 PRESENTATION OUTLINE What is Classification & Reclassification? When and Why Reclassification? Guidelines for Commissioners Methodology for Classification

3 WHAT IS CLASSIFICATION? What is Classification - Iowa Code Section 468: Procedures established under the Iowa Drainage Code to classify the lands to provide for a equitable distribution of drainage benefits per parcel within a drainage district watershed. How to Classify Section : When a levee or drainage district has been located and finally established or otherwise provided by law, or extend any of the ditches, laterals, settling basins, or drains of a district, or required proceedings have been taken to annex additional lands to a district., the board shall appoint three commissioners to assess benefits and classify the lands affected by the improvement. Directions for Classifications Sections : Commissioners to Classify Duties Time for Performance Scale of Benefits Rules of Classification Assessment for Lateral Ditches Reclassification of Benefited Lands

4 WHAT IS RECLASSIFICATION? What is Reclassification - Iowa Code Section 468: The redistribution of benefits in an established Drainage District following the same rules and procedures established for classification. Many Districts have not be reclassified since their establishment in the early 1900 s; are these schedules equitable anymore? When to Consider Reclassifying Section : the Board may consider whether the existing assessments are equitable as a basis for payment of the expense of maintaining the district and of making the repair, improvement or extension. If they find the same to be inequitable in any particular, they shall by resolution express such finding, appoint three commissioners possessing the qualifications prescribed in Section and order a reclassification When Reclassification is Required - Section : When an assessment for improvements as provided in Section , exceeds twenty-five percent of the original assessment and the original or subsequent assessment or report of the benefit commission as confirmed did not designate separately the amount each tract should pay for the main ditch and tile lateral drains then the board shall order a reclassification in accordance with the principles and rules set forth in Section

5 WHEN AND WHY IS RECLASSIFICATION RECOMMENDED? When to Reclassify: If the board of supervisors, acting as trustees for the district, find the assessments to be generally inequitable, based upon an evaluation of the Engineer. (Code ) If separate assessment schedules do not exist for separate lateral district facilities. (Code ) Why to Reclassify: If the current assessment schedule was developed 50 to 100 years ago, there is most likely major changes within the watershed that would affect the distribution of drainage benefits. Additionally, the original classification was done without the availability of modern maps and computer technologies. These provide a means of developing a much more accurate distribution. LiDAR (Light Detection and Ranging) NRCS Soil Maps GIS (Geographic Information System) Computer Software

6 WHEN AND WHY IS RECLASSIFICATION RECOMMENDED? Additional Reasons to Reclassify: A change in landscape has occurred such as an abandonment or construction of a roadway or railway. Over the years land usage has changed such as farm ground permanently removed from production. Therefore assessments should be determined based on the existing conditions that affect the need for drainage. This is especially significant with partial or full urban districts. Landowners should only be responsible for the maintenance and repair of facilities which they receive benefits from. If lateral facilities have not been separated on to individual schedules the board of supervisors acting as trustees for the district should direct them to be. If an improvement to the district facilities are planned or constructed; such as a parallel relief tile or an extension to the open ditch. The distribution of the benefits will change due to these improvements.

7 GUIDELINES FOR COMMISSIONERS Iowa Drainage Code Section fix the percentages of benefits and apportion and assess the cost and expenses of constructing the improvement according to law and their best judgment, skill and ability. The Guidelines Governing Classification, Sections : Inspect and classify lands in 40 acres parcels or less according to legal subdivisions. (468.39) Use a graduated scale of benefits for each tract assigning a classification of 100 to the parcel receiving the greatest benefit. (468.39) In estimating the benefits Commissioners shall only consider the benefits which will be received by reason of the construction of the improvement in question. (468.40) Determine and report separately the benefits received by the main, laterals and sub-laterals. (468.41) Assess benefits and apportion costs to railroad property, public highways, and other public lands. (468.42)

8 METHODOLOGY FOR CLASSIFICATION PRIMARY FACTORS USED: 1 Benefited Acres SECONDARY FACTORS USED: 5 Parcel Elevation Factor 2 Wetness Factor 6 Runoff Factor 3 Proximity to Outlet 7 Other Factors 4 Facility Use Factor 8 Final Judgment

9 BENEFITED ACRES WITHIN THE WATERSHED OF THE FACILITY WITHIN THE WATERSHED OF THE FACILITY LANDS THAT RECEIVE BENEFIT FROM SUBSURFACE FLOWS THOSE PROTECTED FROM OVERFLOW

10 CATCHMENTS AND FLOW PATHS

11 WETNESS FACTOR Inherent drainage need of the soils on the parcel Use county soil survey drainage classification CATEGORY DRAINAGE CLASSIFICATION FACTOR (TYPICAL) SLOUGH VPD 100 WET PD 75 LOW SPD SWD 50 HIGH WD 25

12 WETNESS AND SOILS

13 PROXIMITY TO OUTLET Description: How much closer an outlet is brought. Computed as part of linear distance to the outlet furnished by the facility. Parcel's outlet is assumed to be at the outlet of the facility. Equals length of facility used by parcel's drainage divided by total distance to parcel's outlet. EXAMPLE: Proximity Factor = 13,500 feet of ditch / 18,000 feet of distance to outlet = 0.75

14 PROXIMITY BY PARCEL

15 FACILITY USE FACTOR Description: Portion of the facility through which the drainage from that parcel flows. Begins at zero at the outlet and always increases along the length of the facility. Computed as percent of original total ditch excavation completed or as percent of original total cost of drain tile required to construct the facility downstream of point of water entry. EXAMPLE: Facility Use Factor = (30,000 CY Original Downstream Excavation / 50,000 CY Original Total Excavation) X 100% = 60%

16 USE BY PARCEL

17 OTHER ADJUSTMENTS Adjustments for situations not typical of agricultural land in the district EXAMPLES: RUNOFF FACTOR: Urban areas, roads, railroads and others with greater runoff potential SURFACE/SUBSURFACE FACTOR: Areas tiled across divide into or out of district POND FACTOR: OTHER FACTORS ASSIGNED BY Permanent retention areas such as Municipal waste treatment lagoons, gravel pits, lakes and farm ponds COMMISSIONERS

18 CALCULATION OF CLASSIFICATIONS PARCEL #1 #2 #3 #4 #5 #6 #7 TOTAL BENEFITED ACRES WET FACTOR PROXIMITY USE FACTOR ELEVATION FACTOR ASSESSIBLE UNITS 80,930 15, ,000 30, , , , ,226 CLASSIFICATION (%) CLASSIFICATION/ACRE ASSESSMENT $ $62.08 $ $ $ $1, $ $3,762.28

19 CLASSIFICATION PER PARCEL

20 CLASSIFICATION PER ACRE

21 CLASSIFICATION PER ACRE

22 ASSESSMENT PER ACRE

23 FINAL JUDGMENT Methodology provides the commissioners with an understandable, defensible way to individually consider and account for the many factors which affect relative benefits in a drainage district. Results in fair and equitable treatment of all landowners regardless of location in the district. But, it only yields a set of numbers! The final and most important step is for the commission to judge the equity of those numbers Best method is to place a map of the district classification per acre for each parcel and take, with all supporting calculations, to the field. This allows the commission to best judge parcel-to-parcel fairness and overall equity.

24 THANK YOU. Ivan D. Droessler, PE Brian W. Blomme, PE